Comments

  • Who is morally culpable?
    I didn't vote on the poll since 'none of the above' wasn't a choice.

    Is determinism true? How can we know for sure?Truth Seeker
    Contrary to the popular belief, determinism has nothing to do with this. It has to do with the physics of our universe being causally closed. If it is (deterministic or random), then there can be no objective morality, or as 180 puts it:
    There cannot be a vantage point for us outside of this causal nexus to differentiate right or wrong about assigning "actual moral culpability180 Proof
    :100:

    I don't take it for granted that determinism means you shouldn't hold someone culpable.flannel jesus
    That's the common mistake. Determinism (or any closed physics) means that one cannot be held objectively culpable, which is very different from being held culpable.

    So while there are valid interpretations of physics that are deterministic and ones that are not, the difference is moot. The question is if physics is causally closed. Those that posit objective morality require the cause of one's choices to come from elsewhere than physics, hence the need for physics to not be causally closed.


    I find all this a side track to what moral culpability is. Morals are a product of a society with expectations on its members. If something is not a member of such a society, then moral culpability is meaningless. If you disagree (which I'm sure many do), then provide a counterexample.

    If morals are objective, then the rules of all societies anywhere must be based on these objective rules. So say you're playing dungeons and dragons. The dungeon is not closed. The choices made are made by people outside. There is a moral code that you don't betray your team members. That can only be meaningful if the player has some control over his character in the game. Else the character's actions are determined by the closed physics of the game and those outside the game cannot hold him moral culpable.
  • What is Simulation Hypothesis, and How Likely is it?
    couldn't one adopt the kind of approach that the weather forecasters (and, I believe, physicists trying to work out fluid dynamics, which is probably the same problem) have adopted?Ludwig V
    The weather is closer. Fluid dynamics of a system in stable state (say water moving through a pipe, dam spillway) needs a description of that state, a calculus task. If it is dynamic (simulation of water waves), then it's more complicated, closer to the weather.

    No simulation of the weather will produce an accurate forcast a month away, no matter how accurate the initial state is measured. Trends can be predicted, but actual weather at location X at time T is not going to happen. Similarly, no simulation of people is going to predict them doing what history says actually happened, no matter how accurate the initial state.

    One does not improve weather forecasting by simulating the formation of individual rain drops, but nothing else at that level of detail, yet Bostrom is suggesting that such an inefficient choice would be made on a regular basis, for seemingly no purpose except that his argument depends on it. He clearly isn't a programmer.

    Comment - this possibility high-lights for me a question about Bostrom's first two hypotheses.
    The entire paper is one hypothesis. There are not more that I am aware of.
    Your following description doesn't help in me trying to figure out what you're considering to be 'the first two of presumably more than two hypotheses'.

    That would require us to define what is meant by "post-human" and "extinction".
    I posted his definition of 'posthuman', which is, in short, a level of technology capable of running the numbers he underestimates, and far worse, capable of simulating a posthuman set of machines doing similar simulations.
    As for extinct, there would only be two possible definitions: 1) No being in the universe is biologically descended from what is the Human species today. This of course is totally undefined, since if we're simulated, the actual humans of 2024 may not appear human at all to us. Much depends on what era the simulation uses for its initial state.
    2) The other definition is that no entity in the universe has the human race of today as a significant part of the causal history of its existence. In short, if there are human-created machines that have replaced us, then humans are technically still not extinct. This is very consistent with his choice of the term 'posthuman'. One can imagine the machine race actually getting curious about their origins, and knowing about humans and presumably having some DNA still around, they might run simulations in attempt to see how machines might emerge from that. Of course, the simulations would produce a different outcome every time, sometimes with humans going extinct quickly, or losing all technology and reverting essentially to a smart animal, much like how things were before people started digging metals out of the ground.

    Then we would have to deal with the difference between two different possibilities. We may go extinct and be replaced (or ousted) by some other form of life or we may evolve into something else (and replace or oust our evolutionary predecessors).
    There you go. You seem to see both routes. The third path is extinction, or simple permanent loss of technology.

    Given that inheritance is not exact copy and the feed-back loop of survival to reproduction works on us just as surely as on everything else, can we exactly define the difference between these two possibilities?
    What two possibilitie? Humans that evolve into something we'd not consider human by today's standard? Many species do that all the time. Other possibility is 'ousted' as you put it. Our biological line is severed, as happens to nearly all biological lines given time.

    They say that birds evolved from dinosaurs, and that mammals took over as dominant species from dinosaurs.
    Good example. There are no dinosaurs (which, unlike humans, is a collection of species). The vast majority of those species were simply ousted. They have no descendants. But some do, and the alligators and birds are their descendants. They are not dinosaurs because none of them is sexually compatible with any species that was around when the asteroid hit. They are postdinosaur.

    Which possibility was realized for dinosaurs?
    It depends on the species, or the individual. Mom has 2 kids. One of those has children of his own, and the other is ousted, a terminal point in the family tree.

    Another problem. Given that a feed-back loop is at work on these phenomena, can prediction ever be reliable?
    Prediction of what? A simulation of history makes no predictions. A simulation of the future is needed for that, hence the weather predictors.
    To guess at the question, no simulation of any past Earth state will produce 'what actually happens', especially if that simulation is of evolutionary history. There is for instance no way to predict what children anybody will have, or when, so none of the famous people we know will appear in any simulation. Again, Bostrom seems entirely ignorant of such things, and of chaos theory in general.

    The third hypothesis suffers, for me
    You really need to tell me what these hypotheses are, because I know of only the one. Two if you count the VR suggestion, but that doesn't come from Bostrom. i know of several that support a VR view, but none that has attempted a formal hypothesis around it.

    Anyway, Bostrom posits nothing that is equivalent to a brain in a vat. That is more appropriate to a VR discussion.


    The second premise - any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof) - seems obviously true to me.wonderer1
    It the second possibility. He says one of the three must be true. It's not a list of three premises.
    I agree that granted this super-improbable posthuman state, that indeed, nobody is going to run a simulation of the history that actually took place. It just cannot be done, even with the impossible technology required.

    The simulator would need to consist of more particles than the system which is being simulated.
    If it is simulating at the particle level, yes. I can run an easy simulation of the planetary motions without simulating each bit. Each planet/moon/asteroid can effectively be treated as a point object, at least until they collide.

    That's a rather fundamental problem. In practice, only things that are simpler than the simulator (or things treated simplistically) can be simulated.
    Yes, and Bostrom claims several levels of depth, meaning the simulation is simulating the machines doing simulations.

    It seems to me that the person who would seek to disprove the second premise would need to prove that consciousness can arise in a simulation of something much more simplistic than the world we find ourselves in,
    Yes. If the goal was to simulate consciousness, they'd probably do one person, or a small isolated community (a closed system). And it wouldn't be a simulation of anybody real, but rather just a learning tool to show that a simulated person behaves like we do. If it worked, it would be a big blow to the dualists, but I'm sure they'd find a way to explain the results away.
    The dualists can similarly deal a pretty fatal blow to the physicalists, but they choose not to pursue such avenues of investigation, which to me sounds like they don't buy their own schtick.
  • What is Simulation Hypothesis, and How Likely is it?
    So I wanted to address the Simulation Hypothesis from Bostrom directly.
    I quote only the abstract and a few parts of the intro.

    This paper argues that at least one of the following propositions is true:
    (1) the human species is very likely to go extinct before reaching a “posthuman” stage;
    (2) any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof);
    (3) we are almost certainly living in a computer simulation. It follows that the belief that there is a significant chance that we will one day become posthumans who run ancestor‐simulations is false, unless we are currently living in a simulation. A number of other consequences of this result are also discussed.
    — BostromSimHypothesis
    Posthuman is defined here:
    The simulation argument works equally well for those who think that it will take hundreds of thousands of years to reach a “posthuman” stage of civilization, where humankind has acquired most of the technological capabilities that one can currently show to be consistent with physical laws and with material and energy constraints. — BostromSimHypothesis
    The trichotomy is reasonable, but worded in a misleading way. Point 1 makes it sound like this preposterous posthuman state is somehow inevitable if the human race doesn't meet an untimely demise along the way. This is nonsense since the posthuman state described is totally unreasonable, and human technology seems heavily dependent on non-renewable resources upon which this gilded age depends.
    The computer envisioned is a molecular machine that isn't electronic, but works with levers and gears and such, very small. But it needs a huge structure to supply energy and dissipate heat. The latter isn't problem, but a mechanical computer made of individually placed atoms would be phenomenally unreliable, and would be very size constrained. How does one fetch data from distant locations, using levers and shafts and such? The data set required by the description would require far more molecules than the described device would have.

    The third point seems to suggest that all this fictional processing power would be regularly pressed into service doing what he calls 'evolutionary history', a simulation of our ancestors. This is not just unlikely, but actually impossible.
    Say the people from 100 centuries in the future wants to simulate the world of today. To do that, they'd need to know the exact state of the world today, down to almost the molecular level, and I know for a fact that nobody has taken such a scan. Furthermore, any simulation of that state would last a few minutes/hours at best and then diverge significantly from what actually happened. So a simulation of one's own history cannot be done. At best, to simulate 'evolutionary history', one might set the world to the state of 20 million years ago with many of the species known to exist at that time, and see what evolves. It won't be themselves, but if those running the simulation are not human, then we're the unexpected things that evolves instead of them. That's plausible, but it isn't a simulation of their own history.

    More problems when they claim to simulate the high performance machines that run the simulations later in time. He is after all claiming that there are simulations being run by the simulations. He seem to have no idea how inefficient this would be, that it takes millions of instructions to simulate a single interaction, coupled with all the side effects. I've written code to simulate the running of code (for profiling purposes). It didn't simulate transistors or anything, it just needed to assume that the processor works correctly and simulate at the intstruction level. It still took thousands of instructions to simulate one instruction.

    That's just me tearing apart the abstract. The article goes on to suggest impossilbe future computer speeds, and tasks that are more than even that fictional processor could handle. There's a section specifically about substrate independence, with which I agree. It essentially says that doing it with paper and pencil, electronics, mechanical, etc all work the same. The outcome of the simualtion in no way depends on what substrate is used.


    He does an estimation of 1033-1036 instructions needed to do one of his simulations of human history. Apparently only the people are simulated, and the rest (animals, plants, geology, and much worse, all the computers) are only imitated, not simulated. He justifies this small number with 100 billion humans, 50 years per human, 30M seconds per year, 1014-1017 brain ops per second, which comes to 15 times the figure stated above.

    OK, it takes a lot of instructions to simulate all that goes on during a single brain op, and all that goes on between them. To simulate world history, it seems far more than just brains need to be simulated. At 100 billion people, only about a century or so of history can be simulated, nowhere near enough to get to the point of them running such simulations of their own.
    Why 50 years? Is life expectancy expected to go down? What's the point of simulating minds at all when imitating people (as is done for everything else) is so much more efficient? The only reason is that Bostrom's idea doesn't hold water if you don't presume this needless complication.

    Given future technology, simulation of a small closed system (maybe a person, or an island village) can be done. Actual world history? No actual history of any person, let alone all of them, can be done. Why does Bostrom choose to ignore this?


    So I have to imagine myself as being a sim and not knowing it?Ludwig V
    Yes. That's Bostrom's whole point. He says we're probably all simulated, but it's based on the anthropic reasoning above, which makes many many unreasonable assumptions.
    ~
  • What is Simulation Hypothesis, and How Likely is it?
    Regarding the question "are we in a simulation?" I interpret this as similar to "is solipsism true?" It's impossible to prove one way or another, but nevertheless - it's rational to believe we are not.Relativist
    In that sense, the two are similar. Also, quite often, in both VR and a true sim, solipsism is true, but you know it because there are clues. We here are envisioning a scenario where the simulated reality is good enough that those clues get harder and harder to find.

    Regarding the Turing test: it has been passed - to a degree.
    Cool. I wasn't aware. Nice controlled test, and kind of pre-chat-bot, which is maybe a good thing. I wonder how trained the judges were; where was the focus of their questioning? To pass today with tools like chatGTP around, you'd have to dumb down the machine answers since it 'knows' more than any human, even if the majority of what it knows is wrong.

    Conversely, humans have "failed" the Turing test (https://www.nbcnews.com/news/amp/ncna163206) -- observers inferred that a human's responses were not humans.
    It would seem fairly easy to pretend to be an unintelligent machine, but I presume these people were not attempting to appear nonhuman.
    I administer a small Turing test all the time for unsolicited callers on the phone. Most phone bots record, but don't parse, any of your responses, so usually one small question is enough. That will change soon.
    The voice-response ones (with limited options to traverse a menu) comprehend profanity, the use of which is often the fastest way to get a human online.

    Regarding "true" AI: IMO, it would entail a machine engaging in thoughts, learning as we do, processing information as we do, and producing novel "ideas" as we do.
    Agree. The game playing AI does all that, even if it is confined to game playing. Early chess or go playing machines were like self-driving cars, programmed by the experts, using the best known strategies. Then they came up with a general AI (like AlphaZero) that wasn't programmed at all to play anything specific. There was only a way to convey the rules of the game to it, and it would learn on its own from there. After a few days of practice, it could beat anybody and any of the specifically programmed machines. That definitely meets all your criteria.
    It doesn't pass the Turing test, but given enough practice, something like it might, but you can't gain a human experience through introspection, no via training data from the web. It would have to actually 'live' a life of sorts, and questions to test it should focus on life experiences and not educational facts.


    Progress would not be measured by fooling people, but by showing there are processes that work like our brains do.
    Totally agree. Progress by imitation has its limits, but since a computer is not a human, to pass a Turing test it will always have to pretend to be something it isn't, which is hard to do even well after it has surpassed us in intelligence.

    Benefits include confirming our theories about some of the ways our brains work.
    That is more relevant to this topic. To demonstrate how our brains work, you (probably) have to simulate it. To simulate it, you need to give it state and an environment (all this was brought up in prior posts). The state in particular is not exacty something you can make up. It needs to have grown that way through experience, which means a quick sim won't do. You have to start it from well before birth and run this really complicated simulation through at least years of life, providing it with a convincing environment all the while. Tall order. It would presumably take centuries for a single test to run, during which the hardware on which it is running will be obsoleted multiple times

    Thanks for joining the topic.


    My argument is that if one starts the Turing test by specifying that the subject is a machineLudwig V
    Then the test is invalid, I agree. If you click the link about the test being passed, the judges did not know which conversations were machines and which were people. They did know that there were five of each. Everybody (judges, machines, human subjects) knew it was a test.

    That's why the attempt to distinguish between the two on the basis of empirical evidence (Turing test) is hopeless.
    The Turing test was never intended as a test of consciousness.

    But it might turn out that the machine is more successful than human beings at [medical diagnosis]
    True. Machines can detect skin cancer better than any human, and that's worth paying for (but there's probably a free app). In my case, the non-doctor tech that saw me googled my symptoms and read back to be verbatim the same information google gave me at home, but leaving off the part where it said "see your doctor if you have these symptoms". Obviously no actual doctor was consulted.

    I think that a machine can diagnose some medical conditions. Whether it can imitate diagnosing any medical conditions is not at all clear to me.
    A 3 year old can imitate giving a diagnosis. Its how daddy gets covered by 20 bandaids. And if a machine can give a diagnosis (they can), then why would they have to imitate the ability that they actually have?

    Do you get confirmation about whether your "spots" are correct or not?
    A few are false positives, which are often confirmed by a simple PM to them. The bots don't hold conversations, but rather give single replies to a question, and no more. Short, and often correct but obvious and not particularly helpful. If you reply to a bot-post, the bot will probably not notice it.

    Some are real easy, and can be spotted before they ever submit a single post. Russia was very big on bots that created sometimes hundreds of sleeper accounts that never posted anything. I banned many of them en-masse. Those have dried up since I think Russia closed the internet connection to the world so the public cannot see how the rest of the world views their war.

    Parrots imitate talking. Are they smarter than human beings?
    No more than is a tape recorder. Parrots don't pass a Turing test.

    I thought you said that there were people inside the system. Now I'm really confused.
    In the Simulation Hypothesis, we are the simulated people, the ones inside the system. Do not confuse this with the VR hypothesis where the people are real and only their experience is artificial. Read the OP if you don't get this distinction.
  • What is Simulation Hypothesis, and How Likely is it?
    On the Turing test discussion:

    I think that you are not talking about the same question as Relativist. (See below).Ludwig V
    Indeed. I dragged in Relativist since the topic of Turing test came up, and he suggests that the test is insufficient to determine intelligence.
    The Turning test has nothing to do with a simulated reality, but rather with a device that imitates a human's text responses, as a test of intelligence.

    And if a machine passes the test (it's a text test, so there's no robot body that also has to be convincing), then it exhibits intelligent behavior. The test is not too weak.
    — noAxioms
    Here, you are positing that you are starting with a machine. In that case, the question is whether the behaviour is really intelligent or merely seems to be intelligent.
    Ludwig V
    Here again, the quoted comment concerns the Turing test, not the simulation hypothesis.

    even if the response was intelligent, it does not follow that the machine is conscious or sentient.Ludwig V
    The Turning test is not a test for either of those. There's not even a test that can tell if your neighbor is conscious/sentient. If there was, much of the p-zombie argument would be immediately settled by some empirical test. The whole point of the term 'conscious' is that it is always defined in such a way that is immune from empirical evidence.

    The fundamental point is whether we can even formulate the question without begging it.
    The question is simple. I am communicating with some unknown entity via text messages, much like we do on this forum. The question is, is that with which I am communicating a human or not?

    I don't see begging in that wording. I am a moderator on a different forum, and one job is to spot new members that are not human. They're not allowed. I've spotted several, but it's getting harder.
    I've even been charged human health insurance rates for a diagnosis provided by a machine, and I protested it at the time. They provided no service at all to me, but they charged me anyway.


    The Turing Test is passed by fooling people into believing there's a human giving responses in a conversation.Relativist
    In a text conversation, yes. That's pretty hard to do, and we're not there yet.

    This is feasible today at least within a limited range of conversation topics.
    Well, one of the ideas is to go outside those topics. I mean, none of the chat bots have long term memory, so one of their traits is that they don't ask any questions of their own since they cannot learn. I suppose clarification requests of questions posed to it might count as asking something.

    If the entity was to pass the test, then nothing is off limits. Be insulting to it, or annoying. It should react accordingly. If it doesn't, it's not passing the test. If it does, it is probably already considerably more intelligent than humans, since it requires far more smarts to imitate something you are not that it does to just be yourself. The entity is not human, and to imitate human responses, especially those involving human emotions, would require superior ability. It doesn't require the entity to actually have human emotions. It is not a test of 'is it human?', but rather 'is it intelligent?'.

    What more are you looking for?
    You claimed the test is too weak. I claim otherwise. If it passes, it has long since surpassed us in intelligence. As a test of human-level intelligence, it is more than enough.

    a computer can produce words that sound like it's expressing empathy - but it actually is not.
    It's not empathy, but it very much is expressing empathy. People are also quite capable of expressing empathy where there is no actual empathy, such as the politicians that send their 'thoughts and prayers' to mass-shooting families, but do nothing about the problem.


    On the Simulation discussion:

    You are positing that it is people who are "in" the sim - i.e. (I assume) being fed the data.Ludwig V
    In a VR, yes, exactly that. People are real, and are fed experience of a simulated reality. Every video RPG does this.
    It the simulation case, there is no experiencer in the world running the sim. There are only fully simulated people inside 'the system', and if that system is not closed, the system needs to be fed artificially generated causes from outside. So for instance, if you look up, you see imitation stars, not fully simulated stars.

    This is one of the reasons Tomb-Raider is less abusive of the processing power of your gaming machine than is something like Minecraft. The former is in a tomb, a very confined limited region in need of simulation. Minecraft on the other hand is outdoors, and my son needs to limit his render distance, else the computer can't generate the background as fast as it needs to. So distant things suddenly appear when you get close enough to them, very unlike reality where there is unlimited sight distance. This is only a problem for a VR where speed of computation matters.

    Plus, if I've understood you, you are positing that the subjects cannot communicate with whatever is running the sim
    No. If you can do that, you very much are aware of the creator/creation status. It would be like talking to a god. In a VR, you can talk to the other players, and you can talk to the NPCs if the NPCs have enough intelligence to talk, but you can't talk to anybody outside the simulated universe.
  • What is Simulation Hypothesis, and How Likely is it?
    So how does this question differ from the brain in a vat, from Descartes' demon or from the supposed possibility that we are all dreaming?Ludwig V
    Nothing like dreaming.
    VR has many of the same issues as the first two. The actual simulation hypothesis does not suggest an artificial sensory stream, except necessarily at system boundaries.

    So how does this topic differ from the question what it's like to be a bat?
    We are not bats. It's not about what it's like to be something we're not. We know what it is like to be a human. The question is, how might we (being the subject of simulation) detect that fact?

    I'm afraid I didn't realize what the philosophical background is (essentially, Bostrom).
    Bostrom is half the story. Most popular fictions depict VR, not a sim. Matrix is a good example of a VR, however implausible.

    I don't find the question interesting, because if we posit that there is no way of telling, then there is no way of telling.
    I didn't posit no ways ot testing. But depending on the quality of the simulation, it might get difficult. The best test is probably to recognize that there must be limits, and to test those limits.

    The interesting question is under what circumstances we would accept that something we designed and built is a conscious being, i.e. a (non-human) person.
    The 'can a computer think' topic was sort of about that. I suppose we could copy our own design and build an actual biological human, but in something other than by the normal way. Anything else is going to be trivially detectable. Not sure how that 'built' person would get loaded with experience. It's not like you can just upload software to a human. Doesn't work that way.

    From that topic:
    The Turing Test is too weak, because it can be passed with a simulation. Simulating intelligent behavior is not actually behaving intelligently.Relativist
    There is mention of the Turing test in earlier posts here. Passing it with a simulation is doing it the hard way. We're getting close to something that can pass the test now, but nowhere close to actually simulating the way a human does it. Perhaps you, like Ludwig here, mean 'imitation', which anything that passes the Turing test is doing by definition.

    And if a machine passes the test (it's a text test, so there's no robot body that also has to be convincing), then it exhibits intelligent behavior. The test is not too weak. What they have arguably already does this, since a machine can exhibit intelligent behavior (even more so than us) long before it can successfully imitate something that it isn't. I mean, I cannot convince a squirrel that I am one of them, but that doesn't mean they're more intelligent than me. I've done it to birds, speaking their language well enough for them to treat me like one of their own kind. It's not hard with some birds.


    This is the traditional problem of evil.Ludwig V
    Pain is not evil. I'd never want to change myself to be immune from pain. It serves an important purpose, and not an evil one.
    The problem of evil argument against God only has teeth if you posit a God that has and follows the same moral values as we envision, such as it being an act of evil to create something humans deem evil.

    I wish I knew what the difference is between a simulation and an imitation, a simulation and a mimicry, a simulation and an analogy, and a simulation and a model.
    A statue, puppet, or a speaker blaring bird-of-prey noises to scare away geese, or a wooden duck lure, are all imitations/mimicry.

    A video game is a VR, which, by definition, feeds artificial sensory input to the real player.

    Conway's game of life (the description of it) is a dynamic model. The execution of the rules of that model (on a computer, paper, pebbles on a go-board, whatever) is a simulation.
    They make computer models of cars. The model is a description of the physical car, what parts are where, and what they're made of, how they're connected. The simulation of that model might throw it into a solid wall, or another car at some high speed, to learn how the initial state in the model deforms by the stresses of that collision. Simulations typically serve some sort of purpose of the runner of the simulation.
  • What is Simulation Hypothesis, and How Likely is it?
    I describe human beings, in contexts like this, as our paradigm of a person.Ludwig V
    Remember, we're not worrying about what those running the simulation are calling the simulated things. We're supposing that we are the subjects here, the ones being simulated, and we (and only we) call ourselves human beings or people. That's the only definition that matters.
    It is the people in the simulation that are tasked with finding evidence that they are the subject of a simulation. What we're called by the occupants of the reality running the simulation is irrelevant.

    I have to say, if these beings are to be conscious, I wish you luck in getting your project through your research ethics committee.
    That's kind of like suggesting that God is unethical to have created a universe that has beings that feel bad, and yes, there are those that suggest exactly that.

    My question now, is why not just talk about people living in a different universe?
    I wanted a universe that is simulated, instead of being instantiated in some other way. I do suppose that the simulated universe is a part of the container universe, but it's still a separate universe. That's questionable if it's an open simulation, but not all of them are. Much depends on the goal of running the simulation. Bostrom actually posits what that purpose would be, even if it is a totally naive one.

    the sims you are describing are clearly in the same universe as we are.
    It is the same universe as we are, because I posit that we are the simulated ones. How would be tell if that were true? The topic isn't about how to run a sim. The topic is about what it's like to be one.

    Talking of sims, do you regard chess or (American) football as a simulation of war?
    There are definitely war elements in both, but that makes it more an analogy than a simulation. The do run simulations of war all the time, pretty much continuously. Yay cold war. Those simulations don't simulate the consciousness of anybody, and I don't think they even have people beyond statistical counts.



    I know human consciousness is a fairly hotly contested issue. But does anyone disagree that it involves multiple processes taking place simultaneously?Patterner
    It is a parallel process, yes. Per relativity, simultaneous is an ambiguous term for events, and no, nothing in a any physical system requires spatially separated components of any process to be simultaneous in any frame. Per the principle of locality, one cannot depend on the other (they are outside each other's causal light cone), and thus the interactions can be simulated in any order, serially.
    The computer would likely do the same thing, but a truly serial process would be much like a Turing machine, and incredibly inefficient design, but performance was never the point.

    If we agreed that a process can take place in the scenario you're describing, you cannot write multiple things simultaneously.
    Granted, but there's no need to, per the above comment. Any such transactions can be computed in any order without altering the outcome. Per the principle of locality, no spatially extended process can have a requirement of simultaneous operation.

    A regular computer would do it that way as well, but the big weather simulation machines are often very parallel, operating on large vector quantities rather than single numbers (technically refered to as SIMD (single instruction, multiple data) machines). The cray supercomputers worked that way, but not sure how much modern high-end machines use SIMD architectures. Point is, doing it serially is just slower, but it doesn't produce a different outcome.

    At no time, in no sense, is everything needed for human consciousness happening at the same time in the paper and pencil scenario.
    On the contrary, time in the simulation has nothing to do with time for the guy with the pencil. Our pencil guy can set everything aside for a year and get back to it later. The simulated guy will not notice. No doubt each transaction will have a location/timestamp, and there's nothing preventing multiple transactions (all the transactions in a single iteration of the data) from having the same recorded timestamp. That is pretty much how simulations are done. Here is the state at time X, and then it uses that state to compute the next state at X+<increment> where the increment might be a microsecond or something. It might take a minute for a machine to simulate all the transactions to generate the next state. It might take the pencil guy several lifetimes to do the same thing, so we're going to need that society to train his replacements each time he retires.
  • What is Simulation Hypothesis, and How Likely is it?
    At risk of opening a can of worms, how does 'modern physics' come into it?
    I joined this and other forums to find out how the prominent philosophers (the ones you learn of in class) dealt with modern physics (narrowing the search to recent ones of course) and found that for the most part, they either didn't know their physics, or didn't care about it.
    So I learned physics, or at least the parts of it relevant to the subjects I cared about.

    Relativity threw significant doubt to Newtonian absolutism where there was one preferred frame and time was posited to be something that flows or progresses, that there was a preferred moment in time, and the universe was static, and either infinite age or somehow set in motion from some initial state at some point. Much of religious myths (especially the creation parts) requires the universe to be contained by time instead of the other way around, and this did not become apparent until about 110 years ago. The universe having a finite age is about a century old, and some religious teachings did at least bend with that one and put the creation event there.

    Quantum mechanics really threw a spanner into the gears with suggestions that ontology might work backwards (that existence depends on interaction with future things), that identity of anything (electrons, rocks, people) is not at all persistent and thus I am not the same I as a second ago.

    One can of course pick an interpretation consistent with your preferences and avoid the implications of the ones you don't like, but if doubt is to be eradicated, all the alternative interpretations contradicting the thing of which you are certain must be falsified.


    And who knows what else might get discovered. Nobody saw QM coming, so all these people who held certain beliefs with certainty found themselves to be wrong or at least potentially wrong. So a declaration of 100% certainty is irrational. I mean, my certainty rests on the sum of two numbers (a pair of arbitrary real numbers say) being exactly one other real number, always and anywhere. I don't significantly doubt that, but I still question it. What if it's only a property of this universe that such a sum comes to that one solution and not a different one elsewhere?
    Wayfarer
    Persistence of self-identity over time is not discussed in Descartes
    Indeed it isn't, but the assumption is implicit. It's too obvious to bother calling out explicitly, or at least it was obvious until ~50 years ago.

    Beings are not objects or things
    Your opinion. The opinion of others may vary.


    I was thinking of philosophical zombiesLudwig V
    I knew what you meant, even if Wayfarer chose to reply to what you said instead of what you meant.

    My point is that there is no easy and clear way to state what the Turing hypothesis is trying to articulate.
    The Turing test (The closest 'Turing Hypothesis gets is the Chuch-Turing thesis, concerning what is computable, and is oddly relevant below) is an intelligence test for when a machine's written behavior is indistinguishable from that of a human. The large language models are getting close, and the easy way to tell the difference is to not ask them questions with factual answers. They also are not designed to pass the Turing test, so all one has to do is ask it what it is.

    Suppose that these simulated people are conscious (as they would be if the simulations were sufficiently fine-grained and if a certain quite widely accepted position in the philosophy of mind is correct).
    For me, a conscious being is a person and a simulated person is not a person, so this confuses me. Can you perhaps clarify?
    A simulated person would be a person, just in a different universe (the simulated one). It's likely quite a small universe. You seem to define 'person' as a human in this universe, and no, the simulated person would not be that.

    why isn't 'dubit' a word? It ought to be.
    — noAxioms
    Well, since you have now used it, and I understand it (roughly, I think), it is a word now.
    And it was already used in somebody else's reply.


    It seems to me you cannot simulate with paper and pencil, because it is not an active medium.Patterner
    Not sure what the term 'active medium' means. Googling it didn't help. I can implement a Turing machine armed with nothing but paper and pencil. Per the Church-Turing Thesis mentioned by mistake above, that means I can do anything that is computable, including the running of the simulation.

    The papers hold not a description of how the simulation works, nor a novel about the lives of the characters simulated, but rather are utilized as memory in the execution of the algorithm, which is doing exactly what the high-power computer is doing. Sure, some of the paper needs to hold the algorithm itself, just like the computer memory is divided into code space and data space.
    The pencil exists to write new memory contents, to change what a paper says to something else, exactly as a computer rewrites memory location.

    If you program everything necessary to simulate consciousness into a computer**, but never hit Run
    But I am hitting 'run'. I wouldn't need the pencil if I didn't 'run' it.
  • What is Simulation Hypothesis, and How Likely is it?
    a person is a human being, i.e. an animal. ... Some physical structures are machines, and hence not animals, but I don't see why such structures cannot possibly constitute people.Ludwig V
    There's a contradiction here. People is animal. A machine is not animal. But a machine can be people? That means a machine is animal and not animal.

    But if they are to constitute people
    I think you are again envisioning imitation people, like Replicants. That's a very different thing than the simulation hypothesis which does not involve machines pretending to be people.
    If you're going for an empirical test, it doesn't work. If a convincing replicant is possible in a sim but not in reality, the runners of the sim can see that and know that their simulation isn't very accurate, and the people in the sim don't know that replicants should be different, so they have no test.

    Secondly, where do you get this assertion that machines must lack spontaneity? I mean, deep down, you're a machine as well running under the same physics. I think you're confusing determinism with predictability.

    So I think you are right to argue that some such process as this would be necessary to create a machine person.
    No. The simulation is creating a biological person, not a machine person. Try to get that. Replicants are not grown from a zygote. A replicant can be trivially tested by an x-ray or just by sawing it in half, or so I suggest. Apparently in Blade runner, it was very hard to tell the difference, but that's also a fiction.

    Calculating is widely recognized as a rational activity.
    That's right. Physics doesn't do spontaneous things (quantum mechanics excepted, which is a big problem if you want to simulate that). But classical physics isn't spontaneous, and yet spontaneity emerges from it, or at least the appearance of it. Anything in the simulation would have to behave just like that.

    To me, it makes no sense to deny that computers can calculate. The catch is that such rational activities are not sufficient to be recognized as a person.
    Yet again, no computer is pretending to be a person, so it isn't a problem.

    If you call it a rationalization, you have already decided the argument is invalid or unsound.
    Probably invalid in this case, and yes, I've decided that, but on weak grounds since I have never followed the argument from beginning to a preselected improbable conclusion.

    Would a simulation of agonising pain be actually painful?
    If the simulation is any good at all, and presuming monism, then yes, it would be painful to the subject in question. No, the computer running the sim would not feel pain, nor would the people responsible for the creation of the simulation, despite suggestions from Kastrup that they apparently should.



    The logic of cogito ergo sum is neither rationalisation nor myth, it is the indubitable factWayfarer
    I didn't say that was the rationalization. I even accepted it since it was a reasonable statement in the absence of modern physics. It is him building on that foundation to his later conclusions that is the rationalization, which I clearly spelled out in my post.
    As for it being indubitable, well, I dubit it, as I do everything *. The Latin phrase translates roughly to 'there is thinking, therefore thinker" which suggests process, a state that evolves over time, but presumes (without doubt) that all said states are states of the same thing, which is for instance in contradiction with quantum interpretations like MWI, which you probably deny because it is fairly incompatible with the dualistic view of persisting identity. That denial is fine since nobody can force your opinion, but absent a falsification of the interpretation, the assertion is hardly indubitable.
    And no, I don't accept MWI either, but I don't claim it has been falsified.


    * why isn't 'dubit' a word? It ought to be.
  • What is Simulation Hypothesis, and How Likely is it?
    That it is another universe, is one of hte ridiculous premises required for its probability to be an effective argument. This is what I'm getting - on it's face, its mathematically almost certain we are in a simulation set up by future generations.AmadeusD
    I agree that the logic presented is completely valid, but the premises are outrageous, and the conclusion is only as sound as those premises.

    But the invocations required to actually, practically, in real life take that seriously are unnerving to say the least, and perhaps the sign one is not being honest with themself.. if the theory convinces one.
    I don't take the argument seriously due to the faulty premises. I see no reason to actually suspect that I am a product of simulation, but I also don't rule it out, nor would I personally find it unnerving to actually find evidence that such is the case.
    I do my best to be open minded to any possibility, or at least possibilities where knowledge can be had. So if I'm for instance in a VR being fed fiction, then I have no choice but to make sense of the fiction being fed to me, and to not worry about the inaccessible nature of whatever feeds it to me.


    But you did not go further into the argument. That is the opening argument for the BIV. But Putnam continues on to counter-argue that premises or claims above are necessarily false. If you're a BIV then to say "I am a brain in a vat" is false because you wouldn't be referring to a brain and to a vat. There's no reference at all! There is no causal link to make the argument sound.L'éléphant
    OK. I admit to not reading the whole thing because I was only trying to point out similarities in the issues of BiV and VR, which are often aligned.

    If either has memory of being put in the vat, then the arguments become more sound. Any video game is like that. You have memory of starting the game, and have evidence that you've not spent your life there (although close with some of my kids).

    If it is indeed just a black-box or non-human mind being fed false information, anything that comes out of its mouth referring to anything about the physical world is false.L'éléphant
    I don't follow that. If it says (without evidence) that it is a BiV, then the utterance is true if that is indeed the fact. It's just not something justifiable, at least not if the lies being fed to it are quality lies. So it isn't knowledge, but not all utterances are necessarily false. What about 2+2=4? Is that also one of the lies?

    The simulation hypothesis is a pitfall -- it looks attractive because it allows us to make arguments like "how do you prove we're not in a doll house?" but we fail to recognize the contradiction of the utterance.
    OK, I haven't brought this up, but if it is a true sim (not a VR), the sim is computing the values of a mathematical structure (this universe), which is sort of presuming something like Tegmark's MUH.

    If I am a part of a mathematical structure, somebody computing that structure doesn't enact the creation of that structure, but rather just works out details of that structure that already is, sort of like Pi is (supposedly) a constant that is not just a property of this universe. It can be known in any universe independently, and the ratio of circumference of a circle to its diameter is pi even if nothing knows that. Computing ii is like the simulation. It doesn't create pi, it just makes the approximate value of it known to whatever is running the computation. The sim may work similarly, making this universe known to the runner of the simulation, but doesn't constitute an act of creation of the universe, which doesn't need to be simulated in order for parts of it (us) to be what we are, which is conscious of the parts of the universe to which we relate.



    You said you would start the sim as a zygote. I am asking: what is the difference between this zygote and a zygote in reality?NotAristotle
    Several differences. The sim is run at some finite level of detail. Does it have mitochondria? Depends on the level of detail, if it matters to the entity running the sim. The sim probably cannot run at the quantum level, and the real zygote does, and even deeper if there is a deeper.

    The sim zygote is an open system, and the real zygote is part of a close system. That is a second major difference. Something has to imitate the interactions with the parts external to the system, and that requires making up fiction now and then, and one can attempt to catch contradictions in that fiction. Of course it helps a lot to know where the system boundary is.

    Or is the zygote you are postulating a mere simulation of a zygote?
    Yes, that. You don't need to pre-load the simulated thing with memory of a past consistent with the fake initial state of the simulation. That's the problem we're trying to get around. Don't know why you find this problematic. The system simulated then grows up into a conscious human with real memories of its upbringing, not fake memories planted by an initial state that probably doesn't know how memories are stored. The whole point of the sim after all is to learn these things.



    Per Descartes, I hold that the fact of one's own existence, that one is a subject of experience, is apodictic, it cannot plausibly denied.Wayfarer
    And here I go doing exactly that, not denying it, but having doubts about it to the point of abandoning the realism it fails to explicitly posit.

    Funny that right after I go on about humans not being rational, but being very good at rationalizing. Conclusion first, then an argument that leads to it. Descartes starts with all this skepticism, and builds up from this simple state that, lacking any knowledge of modern physics, leaves him with something he decides can be known with certainty. I'm fine with that, and I'm admittedly not very familiar with his work, but he goes from there to conclude, surprise, surprise, the exact mythological teachings of his own culture and not any of the other thousand choices of other cultures. That's a great example of rationalization. It was his target all along. A more rational progression from those beginnings leads to idealism/solipsism.
  • What is Simulation Hypothesis, and How Likely is it?
    So, you don't think there's any criterion by which we can discern the difference.Wayfarer
    I do think there are ways, but most of the posters are using fallacious methods to justify their assertions.
    I can think of ways, albeit technologically unrealistic, to falsify a VR with multiple people (non-solipsism) in the VR. If there's just one, other methods need to be used.
    For instance, put me under anethesia. To me, I appear to awaken after only a little time has passed. The only way a VR could do that is to put the real person similarly to sleep, and not just pipe in the sensation of awakening after a short time. That fake 'moving the clocks forward' trick only works under solipsism.

    You admit the possibility that you're not actually a real being.Wayfarer
    The possibility that I am a real being already is contingent on the definition of 'real', and not being a realist, perhaps my not believing that has nothing to do with any suspicion of being a product of a simulation.

    Bottom line still is, per my chosen handle: Don't hold any beliefs that are beyond questioning. The worst things to accept unquestioned are the intuitive ones.
  • What is Simulation Hypothesis, and How Likely is it?
    What is the difference between the simulation and reality if you are constructing "simulated people" based on the same historical states that result in non-simulated people? If the physicalness of both systems is identical in all respects, what is the difference?NotAristotle
    Unclear on the question. The difference between reality (which doesn't supervene on something higher) and the sim (which does) is just that. Reality is supposedly a closed system, and the simulation (either kind) is not, and there is one of the places to look for empirical differences between the two.
    As for the 'historical states', I need clarification. I propose a 'system' that is smaller, with one or a few people say who are actually simulated, and the rest are outside the system, not simulated, but are rather imitation appearance (sensory input to the simulated ones) of other people. AI controls these sensory inputs, and if it is good enough, nobody can tell the difference.
    Bostrom gets into this, except all people are in the system, so there are no imitation people, but most other things are imitation. A wall is not particularly simulated, but it still needs to show wear after time. Paint needs to peel. Dead things need to rot, or at least need to appear to. Physics of simple things is often simple, but changes upon close inspection. That's really hard to do in a simulation, but Bostrom is apparently not a software person and has many naive ideas about it.



    I agree, generally. The paper, on it's face, is fairly convincing but it requires such a ridiculous set of premises (similar to the Fermi Paradox) that it doesn't seem all that apt to the Universe we actually inhabit.AmadeusD
    Bostrom assumes otherwise, but whatever realm is running his simulation doesn't need to be a universe like our own.
    As to the Fermi thing, I have opinions, but they're only opinions.


    I’m sure simulations of kidney functions, like other organic functions, may be extremely useful for medical research and pharmacology, without literally producing urine.Wayfarer
    If you or Kastrup expect a kidney in one universe to produce urine in another, then you don't really know what a simulation does.

    That’s the point - simulations may be useful and accurate, but they’re still simulations, not real things.
    But the question asked is how we might know (and not just suspect) that we are not the product of a simulation. A detailed simulation of you would likely deny his own unreality (as you use the word here), and would also deny that his consciousness is the product of his underlying physics. If he does this, he would be wrong about both. I'm not sure what you'd expect that simulation to yield.
  • What is Simulation Hypothesis, and How Likely is it?
    Regarding your objection re: physicalism. The problem with conscious people within/part of a simulation has to do, in my opinion, with the historical necessities of consciousness. That is to say a simulated person does not have the requisite history to be conscious.NotAristotle
    The simulation needs to provide an initial state that provides that history. History is, after all, just state. Hence my suggestion of starting the sim of a human as a zygote since there is no need to provide it with prior experience. But then you have to simulate years of experience to give it that history, but at least you don't need to presume what the mature brain state might be.

    and someone alive must come from someone else who is alive
    It has to start somewhere, so the womb would be outside the system, an imitation womb, empirically (to the child) indistinguishable from a real mother, in every way. I suppose the placenta would be included in the system since it is, after all, the child and not the mother, but when it is severed, the sim needs to remember which half to keep as part of the system.

    People and inanimate objects are not in the same categoryLudwig V
    To a simulation of low level physics, they pretty much are the exact same category, and both have the same problem of needing to exert some kind of effort to keep track of what is the system and what isn't, a problem that real physics doesn't have since it operates on a closed system.

    What keeps the house warm, (not too hot and not too cold) is the entire system including the water, the pump and the radiators, with its feedback loops and not any one component.
    Similarly, a person (and not a brain) is what is conscious. Not even that, because an environment is also needed.

    A computer is arguably more like a conscious being, that it is probably too rational to count as one.
    Irrationality is required for consciousness? A computer is rational? I question both. Deterministic is not not rationality. I do agree that irrationality is a trait of any living creature, and a necessary one.


    If that's the point, we don't need the theory. We all experience dreams from time to time. And we know how to tell the difference.
    Any sim would be distinguishable from a dream state.
    But we can't tell the difference while we are dreaming.
    Sometimes. One is often reft of rational thought while dreaming, but not always. I can tell sometimes, and react to knowing so.



    The weather event would need to be wet and windy, and not just appear to be wet and windy."bongo fury
    Yes, Wayfarer just below quotes Kastrup suggesting exactly that.

    Bernardo Kastrup says you can get a computer to run an exquisitely-detailed simulation of kidney function, but you wouldn't expect it to urinate.Wayfarer
    It would be a piss-poor kidney simulation (pun very intended) if it didn't.
  • What is Simulation Hypothesis, and How Likely is it?
    It doesn't have to be "at any time", it can just be at the start. And presumably a baby could be hooked up to the machine anyway, without any concern for their memories, no?flannel jesus
    Well, the Sim hypothesis (all versions) as how we might know we are or are not in a sim or VR. You're speaking of a VR in this case. Your memories define who you are, and if those are totally wiped, it's somebody else in the VR, not the person who entered it.

    This VR is portraying a world of 2024 to me, a world in which the technology for such a setup isn't going to exist for at least a century. So if I've been put into it some time in say 2200, then all my memories have been wiped, and they're just running somebody else on what's left of my hardware, rewriting it into a new person that thinks it is 2024. Who would volunteer for that?

    Sure, it could be done to a baby who doesn't question the change in environment, but why would anyone take a baby and subject it to indefinite VR? How does anybody in a VR not just atrophy away from disuse of all limbs? People permanently paralyzed have pretty short life expectancies, regardless of how much fun their brain might be having.
  • Boethius and the Experience Machine
    Might such a machine invariably force users to voluntarily exit the machine (provided exit is possible)?Count Timothy von Icarus
    I echo NotAristotle's sentiments. If the guy knows he is in a simulation, he also knows that the virtue he is practicing is wasted, benefiting nothing but shadows of people. Knowing this, he happiness would hardly be maximized. The experience machine, to maximize his happiness, would in short order exit him from it to allow him to practice actual virtue that benefits actual people.

    If he doesn't know he's in the sim, then he cannot choose an option of which he doesn't have knowledge.
  • What is Simulation Hypothesis, and How Likely is it?
    I don't think so. If someone made such a machine, that someone could know enough about a brain to manipulate memories too. They can manipulate your entire experience of your world, why not your memory?flannel jesus
    This would be a violation of the premise, that only the inputs and outputs are artificial, and the experiencing entity itself is left to itself. If you posit that even your memories are open to direct manipulation at any time, then you end up in the Boltzmann Brain scenario, where,such a hypothesis, as Carroll put it, "cannot simultaneously be true and justifiably believed".


    This does bring up a very relevant point though. Let's dumb down Bostrom's scenario (A Sim this time, not a VR). Instead of simulating a planet, we do just one person Bob, born in say 1870. How does one go about setting the initial state of such a simulation? The machine only knows how to do physics at some specific level of detail. It knows what we do: how cells grow, get nutrients, split, neuron and axon interactions and network changes. But it doesn't know how consciousness emerges from that. It doesn't know what it's like to be the person. It cannot set a state if it doesn't know how the memory works, and what memories to give our subject. The only way to plausibly start such a simulation is from a zygote. From there it evolves as an open system, with all Bob's inputs and outputs faked by plausible but not fully simulated surroundings. His mother for instance would be an imitation, one good enough to fool our subject.
    This is what I mean by two kinds of people in a Sim (and three in a VR). Mom is an imitation, outside the open system. Bob is simulated, being the open system.

    The computing capability to do this is possibly something that can be done in the foreseeable future, but running a simulation of a life all the way from a zygote is a long time to wait, and takes an incredible amount of AI to give Bob a realistic and believable environment in which he gets raised.


    A pencil is not an information processing system. A pencil may be part of an information processing system which includes a person and a pencil and piece of paper, but the brain of the person is playing the key role in whatever information processing occurs.wonderer1
    The one (at a time) person operating the pencil and paper was implied. Also not explicitly missing is a society to breed, train, feed, and otherwise support the efforts of the series of people doing the primary task. A big part of that support is replacement of paper/parchment as it decay into unreadability before it is actuall needed as input for a subsequent step. But the computer also needs to do this, and a lot more frequently than every few centuries or so. Computer memory rots and needs to be refreshed a few hundred times per second.
    Point is, all these implicit additions not being explicitly stated doesn't make the statement false.

    To answer your question, a pencil can't process the video file found here.
    That's right. As you point out it would need a person operating the pencil, which, based on your protest above, is something you feel needs to be explicitly specified.
    The video is digital so not even an A->D conversion is needed to get to the part where the video can be digitally processed. I do admit that a pencil is a poor tool for analog signal processing.
  • What is Simulation Hypothesis, and How Likely is it?
    I disagree with this. In the BIV, the brain is a given. That is, human brain.L'éléphant
    Well, to quote the BiV IEP page, very close to the top:
    Or, to put it in terms of knowledge claims, we can construct the following skeptical argument. Let “P” stand for any belief or claim about the external world, say, that snow is white.

    [1] If I know that P, then I know that I am not a brain in a vat
    [2] I do not know that I am not a brain in a vat
    [3] Thus, I do not know that P.
    — iep BiV
    https://iep.utm.edu/brain-in-a-vat-argument/#:~:text=The%20Brain%20in%20a%20Vat%20thought%2Dexperiment%20is%20most%20commonly,experiences%20of%20the%20outside%20world.

    So if P happens to be "the nature of that doing my experiencing is a human brain", then that cannot be known. Sure, the BiV does originally posit a human brain in a vat, but for purposes of the relevance to VR scenario, anything in a VR cannot know the true nature of its own mind, especially if it can prove that the physics that the VR is conveying cannot be the cause of your actions.

    Because the point of the theory is skepticism
    Yes, that's exactly the point, and yet most VR discussions (say the thing that Musk suggests is almost certainly true) fail to be skeptical about his true nature, something for which he has pretty much zero empirical evidence if his skepticism is true.

    If I could experience the real world, then be hooked up to a machine that simulates the same thing I have experienced, seamlessly, that I would not be able to tell the difference, then theory has made its point.
    Why wouldn't you then remember being hooked up to the machine? You only have memories of a world where such a machine is not possible (yet), so an actual transition from reality to VR is not plausible.


    I remember raging arguments at the International Skeptics Society years ago about whether enough monks writing down 1's and 0's could simulate consciousness, like the guy in the comic I posted moving rocks around and simulating this universe.RogueAI
    And did the nay-sayers actually come up with a reason why it could not? The only reason I can think of is that of dualism: Total denial that consciousness can be a physical process at all. It needs magic to fill what are seen as gaps, and a simulation (both computer or paper) for some reason is denied access to that same magic.

    Both you and B-F have yet to justify why a sim on paper is fundamentally different from the exact same computation done by transistors. But it seems a third person is joining the ranks:

    A computer can process information in ways that a pencil cannot. Why think consciousness can exist without the occurrence of information processing?wonderer1
    Same question then: What information can a computer possibly process that a pencil cannot? Time of computation seems to be the only difference, and time of computation is not a factor at all with the Sim hypothesis, even if it is absolutely critical to the VR hypothesis.
    I do very much agree that a VR cannot be done by paper & pencil, but I never suggested otherwise,
  • What is Simulation Hypothesis, and How Likely is it?
    It is unclear to me why there would be more leaf worlds, could you spell that out for me?NotAristotle
    Picture 'reality' R0 as the trunk of a tree. It has 9 boughs (S1-S9) coming out of it, the simulations being run on R. Each of those has 10 branches, labeled S10-S99. Those each in turn have 10 sticks (next level simulations (S100-S999), Then the twigs (S1000-S9999) and the leaves (S10000-S99999). Every one of those simulation has say 10 billion people in it, so a given person is likely to be simulated (all except the ones in R0), and most of those (90%) find themselves in the leaves, the non-posthuman state as defined by Bostrom. So finding yourself in a state where such simulations are not possible is most likely. And this is presuming only 10 simulations per world, whereas Bostrom posits far more, so the numbers get even more silly.

    This argument is a gross simplification, and presumes some outrageous things, for instance, that one world can be simulating trillions of consciousnesses at once, and there are motivations that people would want to run such a thing at all. It also presumes fate: that all initial random states with people in it will almost certainly eventually progress to this posthuman state. It also preposterously presumes the continuation of Moore's law for millennia, and posits no end to non-renewable resources. Those are many of the reasons Bostrom's proposal falls flat.
    How about simulating a quantum universe with a classical machine? That's been proven impossible. I notice Bostrom suggests shortcuts, where the brute simulation needs to know what it's particles are doing and notice when intent emerges from the atoms so that it can actually change physics when one looks closely enough at something. The comedy never ends with that proposal.

    Empirical methods of falsification are also interesting to explore.

    A running process isn't just a succession of maps?bongo fury
    A description of a running process is a map. The process itself is not.

    Do you mean that some part of the computer running the game would need the detail?bongo fury
    It would need to simulate the NPC down to the biochemical level. The NPC would need to be conscious to believe anything, and not just appear to believe stuff. Heck, Elon Musk 'appears' to believe he's in a VR (as a player presumably, not an NPC), but it is questionable if he actually holds this belief. Ditto for a few other notable celebrities that make heavy claims but seem to have ulterior motives.

    Then you're talking about an AI
    An AI is needed to make a convincing NPC that doesn't do its own thinking. It is far more efficient for the actions to come from an AI than it is to actually simulate the character's thoughts and other processes. A pure closed simulation (Sim or VR) needs no AI at all, just brute capacity. No current game has any character do its own thinking, and the NPC are really obviously an NPC since barely any processing power is budgeted to doing the AI better. It's getting better, but has a long way to go before the line between players and NPCs begins to fade.

    Or do you mean that a fictional character described and depicted in the game would need the detail?
    Heck no. A game need only simulate my sensory stream, nothing else. There's no reason to make the characters appear to ponder about what their nature is.

    Have you ever seen this?RogueAI
    I've seen the xkcd thing, yes. I'm not the first to see it. There's lots of references to 1D and 2D simulations in that, but how else are you going to depict it in a comic?
  • What is Simulation Hypothesis, and How Likely is it?
    I think I have heard it said that if a future people decided to make a simulation, they would make A LOT of such simulations. And these simulations would be nested -- simulations within simulations.NotAristotle
    That's pretty much Bostrom's argument, a sort of anthropic reasoned hypothesis that demonstrates a complete ignorance of how simulations work.

    If there are a huge number of simulations within simulations, that means only a small number of these simulations will be simulations that do not have a simulation that they are themselves running. But if we are living in a simulation, we must be living in one of the simulations that is not itself running a simulation. In that case, the odds that we are living in a simulation would be astronomically small.
    That was one of the counterarguments that I think itself fails to hold much water. If each simulation runs several internal simulations, the leaf ones (us) would be exponentially more in number than the base levels. Of course this exponential simulations that are simulating other machines running simulations is a big part of the reason the premises fall apart.

    On the other hand, I do not think we would be conscious if we were "in" what you are calling an actual simulation.
    Why not? I mean, if you deny that consciousness emerges from physical process, then it falls right out of the gate, but presuming physicalism, the simulated person wouldn't act correct if the simulation got the physics wrong.

    For that matter, even under dualism, what prevents the simulated person from gaining access to this supernatural woo like the physical human does?

    In any case, I know I am not living in a simulation.
    How? Incredulity? I'm trying to gather actual evidence for both sides. Lots of people 'know' things for sure, and lots of what people 'know' contradicts what other people 'know'. Humans are quite good at being certain about things for which there is no hard evidence.
    I mean, I don't buy the hypothesis either, but to declare to 'know' such a fact without any logical/empirical backing reduces it to a mere belief, rationalized, but not rational.

    I won't seriously consider the possibility that I'm living in a simulation, or a simulation myself, or a Boltzman brain, or whatever else.Patterner
    This is better worded. It's an extraordinary claim and it requires extraordinary evidence to be taken seriously. The various proponents seem to to use very fallacious arguments in an attempt to demonstrate that evidence.

    Being a Boltzmann Brain thing isn't a proposed hypothesis by anybody. It's simply an obstacle in the way of the validity of various proposed theories explaining how physics actually works. Very few people understand the significance of a BB. Sean Carroll sums it up:

    A theory in which most observers are of the Boltzmann Brain type is ... unacceptable: ...
    The issue is not that the existence of such observers is ruled out by data, but that the theories that predict them are cognitively unstable: they cannot simultaneously be true and justifiably believed.
    — SCarroll
    That means that no observer can have knowledge of the workings of such a universe.


    I am not familiar with any arguments for how physical processes provide an account of the first-person nature of consciousness.Patterner
    I didn't say it did, any more than does the alternative view. The topic surely is discussed in more relevant topics on this forum or on SEP pages. It is a digression here. The Sim hypothesis presumes, as does the last 5 centuries of science, a form of physical monism. There's no hard problem to be solved. There's nothing 'experiencing' you first person.


    .. that the thing simulated is conscious.
    — noAxioms

    Which is to say that a collection of electronic switches is conscious.
    RogueAI
    Well, if you simulating a collection of electronic switches (which a human is, in addition to a lot of other supporting hardware), and you consider that such a collection (the human) is conscious, then yes, the simulated thing will be conscious.



    So, a simulation as a description or theoretical model, distinct from any real or imaginary structure satisfying the description.bongo fury
    The model is perhaps a design of a simulation. The simulation itself is the execution of it, the running of code on a computer for instance being one way to implement it, but paper and pencil also suffices. A simulation is a running process, not just a map.

    Gosh. This?bongo fury
    This is absurd. You're not going to be able to simulate a conscious person with paper and pencil.RogueAI
    You both seem to balk at the paper/pencil thing, but what can a computer do that the pencil cannot? If you cannot answer that, then how is your denial of it justified?

    A novel or a computer game can perfectly well describe or depict a conscious human that doesn't know he is being imagined, and it can equally well describe or depict a conscious being that does know. Detail is neither here nor there. — bongo fury
    The NPC in the computer game would need that amazing level of detail to actually believe stuff (like the fact that he's not being simulated), and not just appear (to an actual player) to believe stuff.
  • What is Simulation Hypothesis, and How Likely is it?
    ChatGPT certainly simulates mental processes (or seems to. More about that in a second).RogueAI
    It simulates no mental processes at all. It answers on its own, not by simulating something that it is not. It is an imitation, not a simulation of anything.

    Do you think it might be conscious?
    That of course depends on your definition of 'conscious'. Most of the opponents of machine consciousness simply refuse to use the word to describe a machine doing the same thing a human is doing.

    Dictionaries define it as 'aware' of and responding to its surroundings, so in a crude way, a thermostat is more conscious than chatGPT. A chat bot has no sensory feed except a network connection from which queries appear, and might possibly not be aware at all of where it actually is, not having any of the external senses that humans do. So by that definition, it isn't very conscious, and it probably isn't one thing, but rather a multitude of processes that run independently on many different servers.

    A true machine intelligence would likely qualify as being conscious (except by those that refuse to apply the word), but it would be a very different kind, since humans cannot spawn off independent process, and cannot distribute their thinking to multiple sites far enough apart that quick communication isn't practical. Biological consciousness is thus far always confined to one 'device' that is forever confined within one head (sort of). Bees exhibit a more distributed collective hive consciousness. An octopus is quite intelligent but has its consciousness spread all out, most of it being in its arms. Machine intelligence would be a little closer to octopuses, but even an octopus cannot temporarily detach an arm and have it act independently until reattached.

    On topic: No machine is going to get smarter than us by doing a simulation. Those are by nature incredibly inefficient.

    Now, when you drill down on "simulate mental processes", what does that ultimately mean?
    It probably means creating a map of brain neurons and synapses organization and running that in a dynamic simulation that not only follows neural activity (and input), but also simulates changes to the map, the creation/deletion of neural connections.


    think that sounds like magic, but everyone else is taking it seriously, so you also have to take seriously the idea that it might not take a whole lot of switching operations to generate consciousness. — RogueAI
    I don't think it takes very many, but to me, consciousness is a gradient, so the question is not if you're conscious, but how conscious. It is more of an on/off thing with a definition like Wayfarer uses, of having first person subjectivity or not. I don't really understand that since I don't see how an device with local sensory input doesn't have first person subjectivity.
    Does my finger have subjectivity? It has first person sensory input, but all it does is send the taken measurement up a wire to be dealt with elsewhere. Ditto for the thermostat. It doesn't react any more to the sensory input other than to convey a signal. So maybe my boiler is crudely conscious because it processes the input of its senses.

    Again, all this is pretty off topic. My boiler doesn't work by simulating a biological nerve system. I don't have the budget to have one that does it in such an expensive, inefficient, and unreliable way.

    So it seems that if we're going to take simulation theory seriously, we should be equally open to the idea that some of the simulations we're running now are conscious.
    ... that the thing simulated is conscious. The simulation itself is no more conscious than is real physics. As I said just above, a sufficiently good simulation of a bat would not know what it is like to be a bat, but the simulated bat would.

    Maybe some of the "creatures" in Conway's Game of Life are conscious. Why not?
    I suppose it would require one to identify a construct as a creature. One can I think implement a Turing machine in GoL, so one you have that, there's little it cannot do.


    Surely the problem is the one frequently pointed out, with the word "simulate" being ambiguous between "describe or theoretically model" and "physically replicate or approximate".bongo fury
    The simulation hypothesis does not suggest that any physical planet (Earth) was created as an approximation of some design/model/real-planet. It is nothing but a hypothesis of something akin to software being run that computes subsequent states from prior states. A VR is a little simpler and more complicated than that because the subsequent states are computed not only from prior states, but also from external input. Sim is deterministic. VR is not.

    So the question occurs, are you holding this

    That means that yes, even the paper and pencil method, done to sufficient detail, would simulate a conscious human who would not obviously know he is being simulated.
    — noAxioms

    up for ridicule, or serious consideration?
    That was very serious. Sim is simply a computation, and any computation that can be done by computer can also be done by pencil and paper, albeit a lot slower and a lot more wasteful of resources. But time is simply not an object. One might consume 50 sheets of paper and one pencil a day, and the only reason it wouldn't work is because Earth would die before you got very far in a simulation of something as complicated as a person in a room.

    A VR cannot be done this way.


    I think [physical processes producing consciousness] sounds like magic, but everyone else is taking it seriouslyRogueAI
    For the last 5 centuries or so, science has operated under methodological naturalism which presumes exactly this, that everything has natural (physical) causes. Before that, it operated under rmethodological supernaturalism where supernatural (magic) was the cause of anything inexplicable, such as consciousness, the motion of the planets, etc. Presuming magic for the gaps contributed to keeping humanity in the dark ages. The other big cause was general illiteracy, but that continued until far more recently.
    My point is, be careful what you label as the magic in that debate. The Sim hypothesis presumes naturalism, and if you don't at least understand that view, then you're not in a position to critique the SH.

    So if I miniaturized the AI hardware and grafted it into the frog, it becomes a simulation instead of a VR?Ludwig V
    No. If you miniturize the VR set (the device that feeds fake sensory input to you, and conveys your responses to the VR) to fit a frog, then a frog can enter the VR just like the human does.
    A simulated frog is just that. There's no real frog running it. It runs on its own. An imitation frog is even worse, and only appears to be a frog to something looking at it, but its actions are faked since it is outside the system being simulated.

    But it is an abstraction from the world in which Conway - and you and I - live.
    From this world yes, but it isn't a simulation of this world.

    I thought we were using "world" in the first sense.
    I'm using 'world' in many ways. There's the world that we experience. If it's a simulation/VR, then there is another world running that simulation, upon which this world supervenes. Maybe that world also supervenes on an ever deeper world, and (as Bostrom hints), it is turtles all the way down.

    Well, I would say that those films are simulations of a fantasy scenario/world.
    I would not say that. They are not 'simulations' as the word is being used in this topic. Those films (any film) are mere depictions of those fantasy worlds, not simulations of them.


    But the idea that VR might be used to deceive people itself presupposes that what is presented by the VR is not real. What might be more troublesome is a VR that re-presented the actual world around the wearer. Pointless...
    Good point, that VR need not involve deceit. One can use a VR setup to say control an avatar in some hostile environment. The military uses this quite a bit, but those are not simulations. Not all VR is a simulation, but this topic is only to discuss the ones that are. I cannot think of a VR into a simulated world that doesn't involve the deceit of making that simulated world appear real to the subject. It actually being real or not depends on your definition of 'real'.

    Are you an idealist?
    No, but their reasoning made a nice counterexample to your assertion that other people are necessarily as real as yourself. In a VR, and even in a Sim, this isn't necessarily true. I enumerated three different kinds of people, each of which operates differently. I suppose I should give them names for easy reference.
  • What is Simulation Hypothesis, and How Likely is it?
    If you're open to the possibility that consciousness could emerge from a computer simulation, are you also open to the idea that consciousness is already emerging in the simulations we're currently running?RogueAI
    Last I checked (which has been a while), they can do bugs, and even that is probably not a simulation of the whole bug, let alone an environment for it.

    As for Baldur's Gate, that (like any current game) doesn't simulate any mental processes, and even if it did, the simulated character would be conscious, but the game is no more conscious than is the universe. It merely contains conscious entities. A computer simulating a bat would not know what it is like to be a bat, but the simulated bat would.


    This runs smack into the 'hard problem of consciousness', which is that no description of physical processes provides an account of the first-person nature of consciousness.Wayfarer
    Pretty much, yea. All the same arguments (pro and con) apply.
  • What is Simulation Hypothesis, and How Likely is it?
    Which aspects of physical processes correspond with subjectivity?Wayfarer
    Not sure what is being asked. I mean, what aspects of physical processes would, if absent, not in some way degrade the subjective experience?

    I think the question unfair. You're definitely of the dualism camp, to the point where you are not open to the idea that a very good simulation of all physical processes of a system containing a human would be sufficient for subjectivity of the human. So VR is your only option if you thus constrain yourself. A human is hooked to a false sensory stream, which in turn is uplinked to the mind attached to the human. Either that or the simulation somehow connects with a mind exactly in the same way physical bodies have.


    Keep in mind that I am not supporting the simulation hypothesis in any form. I'm looking for likely ways to debunk it, but in the end, there can be no proof.


    Clearly, we know that human beings are persons without knowing (in any detail) about their internal physics.Ludwig V
    The idealists for one would disagree with this. Idealism tends to lead to solipsism, where only you are real and all the other humans are just your internal representations (ideals) of them. You've no hard evidence that they're as real as yourself. Of course, modern video games are terrible at displaying other people, and you can tell at once that they're fake. But we're assuming far better technology here where it takes more work to pick out the fakes.


    One needs to specify that "the same" means here.Ludwig V
    'The same' means, in a Sim, that both you and the other thing (a frog say) are fully simulated at the same level, perhaps at the biochemical level. You and the frog both make your own decisions, not some AI trying to fool the subject by making a frog shape behave like a frog.
    Under VR, 'the same' means that the other thing is also externally controlled, so perhaps a real frog hooked up similarly to the VR set, fooled into thinking its experience is native. The fake things in VR are not externally controlled, but are rather governed by either physics or a resident AI that controls how the system interacts with things not part of the system. So for non-virtual things, 'the same' would mean either both self-controlled, or both AI controlled, so there are 3 different kinds of things: virtual control, physical control, and faked by AI. A Sim has just the latter two.

    I'm sorry, what are NPCs?
    Google it. Standard video game term for Non-Playing-Character. It typically refers to a person/creature in a game that isn't played by any actual player, They tend to be bad guys that you kill, or race against, or whatever. In the Sim scenario, it would be a person not actually conscious, but whose actions are controlled by an AI that makes it act realistically. In VR, NPC refers to any person not under virtual control, whether self or AI controlled.

    The 'computers thinking' topic references NPC in several places.


    We can, of course construct, imaginary worlds and most of the time we don't bother to point out that they are always derived from the world we live in.Ludwig V
    Conway's Game-of-Life (GoL) is not in any way derived from the world in which we live, so there's a counterexample to that assertion.

    As here, we know about real cars that really crash and what happens afterwards (roughly). That's the basis that enables us to construct and recognize simulations of them.
    Well yes, since there'd not be much point in simulating a car that crashes under different physics. The intent in that example is to find an optimal design based on the simulation results. Not so under GoL.

    "Star Trek" and "Star Wars" are extensions of that ability.
    Those are not simulations. Heck, the physics of those worlds are both quite different than our own. The Hollywood guys are hardly paid to be realistic about such things.

    We know quite well what is VR and what is not, so it is clearly distinguishable from reality.Ludwig V
    If it's good enough, then no, it would not be easily distinguished from a more real reality, especially since the lies are fed to you for all time. Unl[ike with a video game. you have no memory of entering the VR. Of course all our crude VR does it feed fake vision and sound effects to you. Not the rest. You can feel the headset you're wearing. But even then, sometimes you forget.... It's pretty creepy in some of the scary games.

    Of course, we can frighten ourselves with the idea that a VR (In some unimaginably advanced form) could be used to deceive people;
    Yes, that's the idea (one of them) under consideration here. How do you know it's false? Just asserting it false is beyond weak.

    "Matrix" is one version of this.
    Implausible too, but that's entertainment for you.
    But a good VR is far better than any dream. With a dream, I cannot glean new information, such as reading a sign that I don't already know what says. That's a huge clue that dreams are unreal. I frequently run into that in my dreams, but I'm also too stupid in my dreams to draw the obvious conclusion. Rational thought is far more in the background while dreaming.
  • What is Simulation Hypothesis, and How Likely is it?
    The "simulation hypothesis" is indeed quite different from the hypothesis that there are imitations of people around.Ludwig V
    The bit about imitation people (human-made constructs) is very relevant to the 'thinking computer' topic, and relevant only if not all people/creatures are conscious in the same way (a process running the same physics). The idea is preposterous at our current level of technology, so any imitation people would probably be of alien origin, something that cannot be ruled out. They'd not necessarily qualify as what we term a 'computer'.

    On the face of it, this looks like a generalization from "there are some fake. imitation, simulated people around" to "everything is a simulation".Ludwig V
    OK, if not all the people are simulated the same, then the ones that are not (the NPC's) would be fake, not conscious, but controlled directly by some AI and not the brute implementation of physics that is the simulation itself. There has to be a line drawn somewhere between the simulated system and what's not the system. If it is a closed system, there need be no such line. A car crash simulation is essentially closed, but certain car parts are still simulated with greater detail than others.

    On the contrary, a forgery can only be a forgery if there is such a thing as the real thing.Ludwig V
    Under simulation hypothesis (both Sim and VR), the forgeries are any external input to a non-closed system. Bostrum posits a lot of them.

    In all of these cases, there is always a question what is being imitated or forged or whatever.Ludwig V
    Disagree. The car thing was my example: Simulation of a vehicle that has never existed. Our world could in theory be a simulation of a human word made up by something completely non-human, and perhaps not even a universe with say 3 spatial dimensions, or space at all for that matter. There need be no real thing. I personally run trivial simulations all the time of things that have no real counterpart. Any simple 1D-2D cellular automata qualifies.

    What empirical evidence could possibly confirm or refute this?Ludwig V
    I hope to explore that question in this topic. For one, our physics has been proven non-classical, and thus cannot be simulated accurately with any classical Von-Neumann computer no matter how speedy or memory-laden. But that restriction doesn't necessarily apply to the unknown realm that is posited to be running said simulation. But it's good evidence that it isn't humans simulating themselves.

    Fair enough. But in those [car crash] cases, it is clear what the simulation is a simulation of.Ludwig V
    Sort of. Yes, they have a model. No, it isn't a model of something that exists. There isn't a 'real thing' to it.

    I'm afraid I don't have the time to respond in detail to what you say about actual simulation and virtual reality. Perhaps later. I'll just say that, so far as I can see, the BIV hypothesis either presupposes the existence of normal reality or describes all of us right now. (The skull is a vat.)Ludwig V
    The skull-vat view does not feed the mind a set of artificially generated lies. VR does.

    The difference between Sim and VR is where the mind is, part of the simulation in Sim, and outside the universe in VR. Same difference as between physicalism and dualism. Same test as you would use to falsify dualism.


    Bostrom's speculation has always smelled grossly unparsimonious, to me.wonderer1
    He does seem to throw the resources around, yes. A lot of it presumes that Moore's law continues unabated for arbitrary more time, which is preposterous. We're already up against quantum resolution, and chip fabs requiring nearly maximum practical resources.

    We might be able to simulate a single human in a tight environment (a prison) for a short time. The human would need pre-packaged memories, and thus would not acquire them the normal way, by living a life, unless you have a lot of resources to simulate the growth of a baby to an adult, all withing its tight prison cell (our closed system). The person growing up that way would be pretty messed up.
  • ChatGPT on Replacing Schrodinger's Cat with Human
    I was just trying to paraphrase the Wikipedia article.Michael
    OK, so I spent some time on that article, and apparently the Wigner's friend experiment is something completely different than what I've seen described under that name.
    Maybe it was one of the extensions to that thought experiment, proposed later by somebody other than Wigner, that I am remembering. The article mentions an extensions by Deutsch and others, but doesn't say what those extension are, and I didn't click on the referenced articles.

    Wigner's actual gist is that there are two observers, and one of them knows something about a system that the other doesn't. Each constructs a wave function to describe the system, and the descriptions differ, which is only a contradiction under a version of idealism where actual physical state supervenes on the mental beliefs of humans. Hence only one human can be right, hence solipsism.
    This argument can be made for a classical system, so I don't know what it has to do with quantum mechanics.

    All that is irrelevant to the topic at hand here. We go instead to what I had mistakenly labeled 'Wigner's friend'. I will modify the experiment a bit to get rid of poison and cats. You put observer F in a box (from which zero state information escapes) who subsequently performs a spin measurement on some particle. If it is spin up, he listens to his 8-track copy of "Hollaback Girl" (where the heck did he get that on 8 track??), and if it is spin down, he gets out a deck of cards and plays solitaire for a while. So according to W on the outside of the box, F is in superposition of card-playing (F52) and music-playing (F8). What is it like to F to be in superposition like that? That's what the OP asked of chatGTP, which gave such a wrong answer.

    W subsequently opens the box and F state appears to collapse down to F playing cards, and he reports that everything is quite normal. He did the measurement, got spin down, and what's all the fuss about? This is all in accordance with quantum theory which will predict nothing else.

    The philosophical question goes beyond the theory and asks: What is it like to be F8? Here, various interpretations must be invoked, and the answer varies from one to the next.


    How can a physical theory say anything about metaphysics?Benkei
    It doesn't. None of the interpretations are physical theory, but some of them are metaphysical interpretations of it.
  • ChatGPT on Replacing Schrodinger's Cat with Human
    I also wondered what a chat bot would say about such a thing since there's so much BS in the training material. Bottom line is that science uses methodological naturalism, and hence has a very clear answer tot the question. The only conundrums that result are from when that methodology is denied.

    This thought experiment is well covered in the literature in the Wigner's friend scenario. I notice chatGPT doesn't mention Wigner's friend.

    RogueAI
    ChatGPT]there's a philosophical and conceptual conundrum regarding what the human would experience or perceive during that time.
    There is not. The live human will experience nothing out of the ordinary, and will experience not getting killed. The science is very clear about this. That certain philosophical stances might disagree with this seems to be a problem with the philosophical position, and not with science.

    ChatGPT]as consciousness typically arises from classical processes in the brain, which are not well-described by quantum mechanics.
    If one presumes that consciousness arises from classical processes in the brain, then the answer is clear, but chatGPT apparently doesn';t see it. The conundrum only appears when different assumptions (woo) are made.

    ChatGPT]Therefore, when the box is opened and the human is found to be alive, asking the human "what was it like to be in a superposition?" might not yield a meaningful answer. The human's subjective experience would likely begin at the moment of observation, just like our experience when waking up from a dreamless sleep or regaining consciousness after anesthesia.
    Ouch. So it says the human will not remember being in the closed box. Science says nothing of the sort.


    The cat isn't in a superposition the particle triggering the poison is.Benkei
    The cat is entangled with the particle state, so it, and the bottle, are all very much in superposition. Keep in mind that there's pretty much no actual way to do it with a cat. They've done it with macroscopic objects, but only by putting it in conditions under which no living thing would survive. The problem is the box. The box must be something that can hold a cat, and yet can prevent any information about the box contents from escaping. Maybe if the box is put in deep space and is surrounded by multiple shells of shielding, none touching the others.

    I believe Schrodinger's rhetorical point was to drive home the absurd nature of superposition with a life-size example.Wayfarer
    It was, because the outcome was considered absurd at the time, but no longer. Schrodinger also envisioned a simple iron box, which hardly works. But then, Copenhagen was the only interpretation around at the time, and it was an epistemological interpretation, and epistemologically, the cat state is simply unknown (indeterminate as you put it). But it turns out that one can perform an experiment to demonstrate the superposition of macroscopic states (this has been done), so the absurdity turns out to be reality.


    This is Wigner's friend.

    Wigner observes John.

    John measures a particle spin but doesn't tell Wigner the result.

    From Wigner's perspective, is John in a superposition?
    Michael
    Yes, the OP describes Wigner's friend, but your summary doesn't. It has nothing to do with somebody holding a secret. It has to do with putting a human in the box. This is an attach against the Wigner interpretation, the only interpretation where humans play a significant role. Wigner himself abandoned the interpretation because it leads to solipsism.

    We had a long thread on Wigner's friend alreadyBenkei
    You should have linked the thread

    Michael quoting Wiki:
    According to objective collapse theories, superpositions are destroyed spontaneously (irrespective of external observation) when some objective physical threshold (of time, mass, temperature, irreversibility, etc.) is reached.

    OK. Those sorts of thresholds seem to limit what one can put in a box. It isn't a spontaneity thing, it's a thing simply too energetic to isolate into a closed system.

    in any case is not a state of being but a consequence of epistomological limitations of knowledge of a given system.Benkei
    Only an epistemological interpretation (old Copenhagen) would say this. Pretty much all interpretations since are metaphysical interpretations with describe what is, not what any particular observer knows. Humans play no special role in wave function collapse, except in that solipsistic Wigner interpretation.
  • Time travel implications with various philosophies
    But if iteration isn't permittedsime
    Not sure what you mean by iteration, or 'permitted'. It's a loop, an instance of reverse causality. It's one loop in our example, and it just is, per non-presentist framing of the situation. There is no 'changing of the past'. I gave an example of a worldline that traverses the loop twice, so that might constitute iteration, but you don't seem to mean that sort of thing.

    if iteration isn't permitted then is sending information backwards proof of a loop?sime
    Not sure what kind of evidence you'd consider proof. We have a CTC, which probably involves some huge machine that impossibly makes the right kind of exotic matter needed to hold some sort of pipe open, an effort that must be made at both ends. The empirical appearance of that is something like a white hole, an event horizon out of which stuff comes, but nothing can go in.

    On the smaller scale, we have a crystal ball which gives information from 'the future'. It's the same thing, but scaled down to effectively a ticker tape. Yea, a human could pass through that, but only if scan/copy/reproduce technology exists.

    So evidence (proof as you call it) would constitute some kind of information of something unexpected that turns out to be verifiable in subsequent time. And yes, sports scores (and to a lesser degree stock prices) are kind of the default thing of this sort, having been used in discussions and fictions.

    For if contradictions are ruled out a priori, then what justifies the use of a loop topology?
    We wanted an example of time travel that didn't directly contradict Einstein's theories. It is a straw at which we can grasp.

    E.g suppose that it is possible to send sports results backwards in time. If this action "changed" history,
    If it changed history, then it isn't a CTC (a loop). It would be more of a branching interpretation where multiple histories are meaningful. You can't prove that the branching interpretation is time travel either since it is valid to interpret it as sideways travel, not backwards or forwards.

    then many people (including myself) would interpret this as merely referring to the action producing significantly non-local effects in our present, so that we can preserve the meaning of the word "history" as referring to immutability.
    All actions produce effects. Non-local meaning retro-causal? But you've no evidence of history having been changed unless a history book (the sports score say) comes back, and is demonstrably different that the changed history that subsequently plays out. But in that case, you just assert that what came out of the portal wasn't from the future, but just random wrongness. Sports outcomes very much would be subject to change by a machine predicting its outcome. In the CTC, there is but the one history, consistent with the information from the loop.

    On the other hand, if the action cannot "change" history, then what is the proof that anything has actually been sent backwards?
    The sports game being correctly predicted is pretty good evidence, albeit not proof.


    To return to the presentist reasoning I sketched earlier, It is logically consistent to believe that the past of our world is generated 'on the fly', as in a roguelike video game that generates the content of the game world as an effect of the adventurers present actions.sime
    I'm unfamiliar with such games, but the stance seem to be a valid one. I've been known to argue that given a premise of the principle of locality, ontology sort of works like that, but caused by interactions, not actions or knowledge.

    In such worlds it might appear that information is sent backwards. E.g the adventurer is in an unknown dungeon with a closed door. Only after he opens the door does the game decide what lies beyond the door.
    Not at all unlike Schrodinger's cat. But that's not information being sent backwards. Maybe the magic spell is an exception to that, but I don't know the details. At no point in the past does the thing behind the door get information about the future actions of the adventurer, any more than does the cat.

    Notably, players don't typically interpret "history change" as time travel
    That's good because nobody is finding himself suddenly in a prior time.

    when an adventurer uses a magic spell to re-roll the state of the dungeon around him, but merely as magic affecting the global state of the present. Amusingly, a philosophical dispute once arose between players of the single-player roguelike game Nethack. In that dungeon crawler there exists the "Potion of Amnesia", which if drunk by an adventurer causes the game to delete it's record of the adventurer's knowledge of the game world,whilst leaving the actual game world in tact, meaning that the player must rely on their personal memories when their adventurer navigates and relearns the content of old locations.
    The monsters behind the door don't get re-randomized? Does it place the player in the prior state as well, doors unopened, health reverted, dead friends un-killt? That would arguably be a time travel spell, but unprovable because information (the wiped memory) didn't go back with it.

    But isn't that cheating? Shouldn't a true potion of amnesia change the world itself? Players are divided.
    It's just leverage of a dualistic mind. The adventurer's 'mind' (wiped) and the player's mind (not wiped).


    For me, in fiction, there are 3 basic models of time travel:

    1. One univerese, you can't change the past, just re-enact it. This is like 12 monkeys. When you go into the past, you can certainly do stuff and feel like you're making choice, BUT those choices are already necessarily part of that past - your actions during your time travels are a necessary part of the past and were already a part of your history, you just didn't know it.
    flannel jesus
    Sounds like the epiphenomenal time travel first mentioned in the OP. There is zero violation of physics with that one, and is equivalent to stepping out of a cinema to cross the hall and watch a different movie, perhaps the same one, but back at the start of the story.

    2. One universe, you CAN change the past. This is probably what most people imagine when they talk about time travel. Pretty sure Back to the Future was like this.
    Yes, the fictions are kind of full of this, but it is empirically a branching interpretation. OK, BTTF has the photo or something that is evidence of it being one universe, but that trick is entirely inconsistent with any valid view.

    When you go back to the future, the future you go back to is different from the future you came from, because the past is different now.flannel jesus
    That part is empirically consistent with the branching model, not any one-universe model, unless the machine has omnipotent powers to actually recreate the entire universe. This whole bit was discussed (ad nauseam) in the other thread, coming to one conclusion that this sort of time travel (one universe, getting altered) has a very low probability of survival.

    3. Parallel timelines. When you go back to the past, you're not going into your OWN past, you're jumping into a parallel universe that's the same as your universe, but in the past.flannel jesus
    That's the branching interpretation. The parallel universe has no history prior to your appearance, but they don't know that.
    It is arguably not time travel (per my prior arguments), but rather sideways travel.
    They can't be travel to pre-existing parallel lines, because if you can travel to those, then one can travel back to the other one from which you came, which is still a loop, with all its problems.

    You can make choices in this universe that are different from the past of your own universe, BUT your own universe is still chugging along into the future without being affected by these changes.
    That statement presumes that universes 'chug along'. I agree that the old world still exists, and perhaps 'you' don't even leave it when you travel to another world. There's two ways it can happen: You vanish from the one world, or you don't, and there is now two of you, one in each world. The latter is far more consistent with MWI and with physics. I've not really yet done a post on this point since nobody has expressed interest in that scenario until now.


    You and others have proffered fanciful alternative realities, curly time, elastic time, ragtime, Miller time or whatever, which I admit to not reading with close attention.
    Bottom line: No, you can't travel in any of them.
    Vera Mont
    How very elegantly argued. I see you even have gained toady support.
    I personally came to the same conclusion, but only due to the inability to deliberately create/manipulate the exotic matter necessary, and the OP (had you actually read it) makes the necessary presumption that this restriction isn't there, it having never been proven.
  • Time travel implications with various philosophies
    Not to let the main track die, let me poke at the dualism implications.
    If there is a dualistic mind/body relationship, the identity convention is usually tied to the mind, at least in a view where the mind has an identity.
    So perhaps MWI would be incompatible with such a view since the mind can only 'be' one body, and the ones in other worlds are either p-zombies or not real. Not real is simply denial of MWI.
    But if the mind is a different sort of substance, or a different property of matter, then it still has location and travels with the time traveler, and the magic mind gets cloned along with the body. Such a view would be compatible with MWI and with time travel. For that matter, eternalism isn't entirely compatible with a lot of notions of dualism. I could start a whole different topic about this, but I fear that my naive understanding of dualism would just fill the OP with straw man arguments.

    The only way I can see dualism (true separate supernatural entity version) being compatible with eternalism is via some kind of epiphenomenal relationship. It's no wonder they're all presentists.


    Well. Cannon ball trajectories (roughly) form a parabola over time. The position (spatial) can be expressed as a function of time. Physics. (High school if memory serves.) Meaningful, reliable.jorndoe
    Agree with all, but it is Newtonian physics, the stuff of 19th century and before. Reliable indeed, since that's what was used to put people on the moon.
    Interestingly, Einstein did away with the Newtonian concept of gravity being a force. The cannon ball actually goes straight (follows a geodesic to be more precise), and it is the ground that approximately follows a parabola since it is the ground experiencing the force and is thus accelerating per F=ma. Sure, the ball follows a parabolic trajectory in the accelerating reference frame of the ground, but that's a coordinate effect, not an example proper acceleration.

    There are different species of time?Vera Mont
    Solid evidence that you don't even read the posts, and confirmation of my earlier assessment.
    The three kinds have been enumerated in multiple places above.

    I suspect the time to which you refer is a fourth kind: one that has a location in space, is tangible, and that, if you traveled to where it is, you can step in it. I can add that one to the list and call it straw time.
  • Time travel implications with various philosophies
    I think that the concept of non-local causal cooperation that you allude to is interesting and useful, but i think CTCs are empirically inconsistent and theoretically unnecessary. For any proposed loop, if you could experience going around it more than once, then the proposed loop would be falsified (since the second iteration would be distinguishable from the first). But if you cannot experience going around the loop, then how you do know the loop exists to begin with? A theory containing a CTC cannot have empirically observable consequences on pain of contradiction.sime
    I am going to disagree, but draw a similar conclusion for different reasons.

    First of all, a CTC doesn't come in iterations, so if there's a loop, it's like a portal that's open for a while. One can go through (back a day say), and do it again in a day, but not a third time. That's not a contradiction since there's no iteration, only one loop with two different people going through, possibly holding hands. Secondly, no person needs to experience the trip. The loop is likely not something a living being can survive, but getting information through is enough. If at the past end of the loop, data is received concerning news of tomorrow (such as a sports score), that is evidence that it worked, without anybody having to experience it first hand. The sports score constitutes an empirically observable consequence.

    OK, so why it might not work seems to come from the requirement for a unification of relativity and quantum mechanics. Relativity is strictly a classic deterministic theory. Any describption of spacetime curvature is a deterministic one, but if action needs to take place at both ends of the CTC, that action is conditionally going to take place at some computable probability. The future unified theory would have to be able to describe that, a sort of probabilistic shape of spacetime, which would involve completely different ways to describe it than what GR says.
    Point is, while the current deterministic GR theory allows for a CTC, the new one may have no way to describe it. This is similar to Newton's theory allowing the generation of a uniform gravitational field by various methods, including an infinite sheet of material with some known mass density per area. Under the replacement theory (GR), there is actually no way to describe that sheet, and thus a uniform gravitational field is not possible under GR.

    So to illustrate my concerns, suppose the sports game score is a function of some quantum measurement. There's a probability of it being this, and also of that, and maybe the game might be cancelled. So the information going back through the CTC (which only probably exists in the first place) might be all of those, unreadable. If a person goes through, different people from different futures might all come through, despite only one going in at any given future event. This was mentioned above with the MWI implications. If it's possible that any score might come through, it might be possible that all of them do.

    Time travel opens the door to the concept of "can do otherwise" since suddenly the state of things allows a person to empirically witness different outcomes. Imagine the free will implications.


    Apologies ↪noAxioms, didn't mean to distract the time travel discussion.jorndoe
    No worries, but I'll leave it mostly to you. There's not much traffic that you're interrupting, but you're banging against a wall with your efforts. Opinions held deliberately in ignorance are not usually changed. Evidence of that:

    Okay. So time is a physical entity, with form, spatial co-ordinates and dimensions, which co-exists with the world in which we experience time only as processes, events and changes. In theory, a person can step from the 3-dimensional world into the stream of time and back again.
    The body of evidence for this is found in which scientific discipline?
    Vera Mont
    There is no body of evidence supporting the picture you just described.

    You still haven't identified which kind of time you're making all your assertions about.
    That's perhaps understandable given your deliberate efforts to remain ignorant of, as I put it, the last century and a half of physics.
  • Time travel implications with various philosophies
    For any proposed loop, if you could experience going around it more than once, then the proposed loop would be falsified (since the second iteration would be distinguishable from the first).sime
    That was sort of the main simple example in the SEP article. Fred sneaks into a museum, steals the time machine, goes back a bunch of years, and donates the machine to the museum (explaining what they're doing with one). He doesn't use the machine again, so nobody goes around twice. But the machine violates entropy. It cannot have an odometer or any other evidence of age without invoking the contradiction you point out. So the machine (never created) is self perpetuating, and will do so forever according to its circular worldline.

    But if you cannot experience going around the loop, then how you do know the loop exists to begin with?sime
    A time curve doesn't require 'the same thing' going around more than once, but if one end is in the light cone of the other, it's technically closed, and thus a loop. It has little to do with 'experience', but one of the presumptions of the definition of 'time travel' is that a person does it, not just his dog or his class ring.

    A theory containing a CTC cannot have empirically observable consequences on pain of contradiction.sime
    I don't think this is true, but the dangers are definitely there. A CTC would be by definition consistent with itself, but that means that any information going back cannot be leveraged for the purpose of preventing the future state of the other end of the thing. So a closed loop can be (must be) contradiction free, but it seems to allow the contradictions, which is unacceptable.

    So a CTC can at most be an uninterpretable expression of mathematical convenience rather than a representation of a physically verifiable entity.sime
    I don't think I in any way presented a sound rebuttal of that conclusion.

    As for archeology, how do you know that the practice isn't retrocausal? Consider that the effect of digging into the ground can be expected to produce both predictable consequences that we might call "forwards directed" e.g the dig producing a hole next to a mound of earth, as well as unpredictable consequences that we might call "backwards directed", e.g the dig revealing of a Roman hoard of treasure.sime
    I'm sorry, but the Roman hoard isn't backwards directed. The Romans were first and caused the hoard. The dig did not. Archaeology was my example of forward causation that didn't involve light the whole way, unlike say 'looking at' light from a star 100 million light years away.

    For why should the hoard of treasure be assumed to exist before it was discovered in the hole?sime
    Under what view would it not? Idealism, sure, but they don't ever think it exists, only the experience of it. While I don't presume counterfactuals, the hoard doesn't count as one. I'm not considering any epistemological definition of things unless specifically discussing a view where such things are fundamental. And the archaeologist is very much getting credit for the epistemological existence of the hoard.
    I think even idealism has only forward classical causality. First dig, that causes knowledge of hoard, which causes ideal of Roman story, all in forward progression. The Romans are not in the past. They're the last step, the story crafted.

    why should the hoard of treasure that was unearthed be assumed to exist prior to the establishment of the archeological evidence that they determined day before?sime
    Depends when that assumption of prior existence is being made. The answer is quite different if you've already dug it up.

    So in short, i think the concept of non-local causal cooperation (Synchronicity?) is a causally permissible concept that aligns with experience, but I cannot say the same about closed time-loops.sime
    I'm unclear on how your example illustrated non-locat causal cooperation. Sometimes I'm a bit slow.

    I do not know with any certainty how long "the present" is.BC
    In language, the duration is context dependent. Mathematically, only zero duration avoids contradictions.
    I've seen arguments about quantum time, where the duration between successive moments isn't infinitesimal, and has no 'nows' between them, at least not at a given point in space.

    I do not understand how the past can be meaningless.BC
    'The past' can be meaningless since it means 'times prior to the present', which, in the absence of a view that includes a premise of the existence of 'the present', renders the the phrase about as meaningful as 'one KM northward of the teapot that orbits beyond Jupiter'. That phrase simply doesn't define an actual location in space without an additional premise of the existence of the teapot out there. If the premise is made, then the phrase has meaning, even if the location of the teapot is unknown.


    You have a pastBC
    If I went back a year,
    — noAxioms
    There is no there there.
    Vera Mont
    Your opinions. They're fine, but only opinions, and as stated above, much of the discussion revolves around a different view where there is a there there.That view isn't falsified by assertions and laying and kicking legs in the air.

    Physics has moved on since this 19th century view. I suspect you don't deny things like the big bang or black holes, but both of those come only from a theory that denies your assertions.

    Isn't it more that events have temporal locations?
    Anyway, duration and simultaneity are meaningful enough, and suggest some temporal structure taken together.
    jorndoe
    Simultaneity seems only meaningful in coordinate time (if there is no teapot time), or teapot time if there is.
    Your input is appreciated. An open mind sees more than one valid interpretation of things.
    Why do these topics always devolve into presentist foaming about an alternate view of which they've no understanding?


    What archeologists look at is bits of pottery and and metal and walls that they dig up in old habitation sites.Vera Mont
    In what way is that not forward causality. I mean, I think that sime above attempted to explain something on those lines, but not sure if I got it.
  • Time travel implications with various philosophies
    I do not believe time travel is possible.BC
    I'm not saying it is, but that simply isn't the point of the topic. In a stretch, it could be, especially with exotic matter. Thing is, exotic matter, while mathematically consistent with theory, is not something that can be manufactured or manipulated.

    So within reasonable confines, what if it were possible? What would be the implications of all the points I brought up?

    I look at the past as a crystal
    I personally don't put a whole lot of stock into the concept of 'the past', and most (but not all) of my discussion kind of assumes the concept is meaningless.

    God ... has not, according to our founding fictions. seen fit to do over any part of the past.
    OK. And what if God has seen fit to do exactly that, but not write about it? What would that be like? It's a valid point, and one that I neglected to include in my list.


    But you did say:
    ":SEP envisions time travel ... to a destination time selected"
    Yes I did say that. Travel to a time is like travel to a spatial location, and not to a place where 'space' is stored. Time travel is no different in that respect.
    Vera Mont
    This means a physical body in a physical container, being transported from a point of departure to a destination, which would have to be an actual place where an actual body can land.
    Pretty much, yea.

    messed-up, unverifiable memories don't count.
    No memory is completely verifiable, so I disagree with this statement. If I went back a year, I could make some (but not all) predictions about things I remember, so that very much does sound like a verifiable memory. I say 'some' because I'm a firm denier of fate, and my presence a year ago would change many things. The BTTF sequel with the sports almanac wouldn't work, but predicting comets and close meteor encounters would.


    In block terms, time travel is either a discontinuous worldline, or a worldline that isn't everywhere time-like.
    — noAxioms
    The what now?
    It's spacetime terminology from relativity theory. Hard to discuss that if you're unfamiliar.
    I do realize that I am posting in a forum with members often unfamiliar with the physics involved, but it is after all a philosophical topic that doesn't belong in a physics forum. But I also don't see how proper philosophy on most of the above mentioned topics can be done by anybody not familiar with recent (at least up to 1960) physics.

    The most you can hope for is that someone in the past made a faithful virtual recording of some aspect of their world, and you can access that recording through some device. Like old movies.
    Anyone can look at the past, which isn't any sort of retrocausality. I mean, that's exactly what hte archaologists do. It's looking forward or causing some effect backwards that's the trick. Most of the plausible scenarios I have in mind require cooperation at both ends. No travel to a time that isn't expecting you, but rather a portal deliberately held open at both ends to let information or more through. So in that scenario, there's no 'changing' of the earlier time since the travel back to that point was always there. That's the nature of a CTC. SEP had some examples of this, but I find them implausible.



    So to pick one of my points, I start with identity since so many other points rely on it. I have a cloning booth with three doors. A person walks in the middle door and that person walks out of both of the other two doors. The question is, which is the original? This contrived scenario is deliberately symmetrical, but with time travel or mere teleport machines, the symmetry usually isn't there.
    This well might happen naturally all the time such as with MWI, but nobody sees both of the clones, so the convention is easy. The one you see is the original, and the one you don't isn't. Each of them considers himself to be the original, and that's not a contradiction because there's no evidence of one.

    With a teleport/cloning machine where the clones can interact, that convention falls apart, and a new one is needed. It's a convention, meaning a deliberate choice. It's not something that can be physically verified because physics is mute on the topic.
  • Time travel implications with various philosophies
    Thank you all for your initial responses.

    time has no physical locationsVera Mont
    Well I didn't say 'travel to where they keep time'.

    Time travel seems to be the presence of a person with memories of another time (a future time, or a discontinuously past time). A coma accomplishes this, but is trivially dismissed as mere 'waiting'.
    In block terms, time travel is either a discontinuous worldline, or a worldline that isn't everywhere time-like.

    I don't think there is any hope for time travel.jgill
    No argument, but also not the point of the topic.

    Do we know if time exists outside of human cognition?Tom Storm
    Well clocks measure a kind of time (proper time), so that type is real, at least if you consider the clock to exist outside Human cognition. Coordinate time is another type, and that one is purely an abstraction (or it is under relativity, but not so much if you don't accept its premises).
    Then there's the 3rd type of time, which is the one usually meant when asking the question of if time is real. It is sort of the progression of the present moment. Like the teapot orbiting past Jupiter, there is zero empirical evidence for it,

    So it seems that the latter two qualify as a product of cognition, but certainly not limited to human cognition.

    The important question here is costBC
    Engineering issues are not a concern to this discussion, only the implications on current philosophies if it could be pulled off.
    I am dismissing the Disney-version of time travel, where the entire universe is destroyed and rebuilt as a replica of what the machine thinks the selected time ought to look like. That's giving it omnipotent powers far beyond mere cost.

    the thrill of watching T Rexes mateBC
    It was brought up elsewhere. If you go to watch the T Rexes mate, you either were always there, or you changed something. If a change was made, there's no going back to the world from which you departed. Humanity beyond what you brought with you is gone.

    What that is like to the people you left behind is one of the items of discussion. A similar answer to the caveat emptor query.

    Your post seems to presume a sort of growing block model, which is absolutist, and classically causal in nature. You can go with that assumption, but the conclusions would then only follow if that premise was true.

    The universe is in a state at one moment, then another state in the next.Philosophim
    This part is specifically absolutist, since the assertion isn't true without a preferred foliation of all spacetime events.

    The reason why the universe is in one state is because of the forces and matter in the previous state.
    This implies the classical causality. In a classic sense, this works, but given closed time curves (CTC), there is not an objective ordering of causal events, and CTCs are valid solution in relativity theory. I'm not sure how growing block handles a CTC.

    Meaning that if we could reshape the forces and matter to what it was 1000 years ago, we would be in the state of the universe 1000 years ago. But we can't go back.
    'Reshape' is the omnipotent power thing I'm disallowing, so we either utilize one of those closed curves, or we actually 'travel' to 1000 years ago and make some local difference (similar to wave function collapse) that spawns a different causal progression from the mildly altered state (similar to MWI).

    There is only now, and what was before.
    That finally seems like a direct assertion of growing block view. You can 'go to' the past since it exists, but you can't go to the nonexistent future. But growing block says the past can't return to the state of 'is happening', so at best your presence there would be epiphenomenal, or again, the creation of a new branch, which is more sideways travel than backwards.
  • Time travel to the past hypothetically possible?
    You refuse to acknowledge that Floyd at noon is but a 3D part of a 4D object.Luke
    I don't consider it a 'part', no. I don't see perdurantist language in the field, so I don't use it. A part of a 4D object would be a smaller 4D object. A finite number of parts make up a finite whole. The 3D cross section you describe corresponds to a state of Floyd in presentism. Floyd is in one state at noon, and a different state at 1. None of those states move since each is at but one location ever. But Floyd is still said to move in presentism. Your argument seems to be equivalant to Floyd not moving because none of his states do.

    I do acknowledge that the perdurantists would say that Floyd at noon is a 3D part of a 4D object. I don't really approve of that for several reasons, all of which I've stated, but ambiguity being a big one.

    I will also say that, given a frame of reference to define the hyperplane of simultaneity referred to as 'at noon', then 'Floyd at noon' defines a set of events that comprise a 3D spatially extended region, and that those events are a subset of all the events that are considered to be Floyd.
    That's pretty close to the perdurantist wording, but without all the ambiguity and terms with loading meaning. Funny thing is, the statement works under presentism as well, except the specification of the frame wouldn't be necessary.

    The noon-part of Floyd doesn't change its temporal or spatial location, like you assume.
    There you go again, putting straw man assumptions in my mouth.

    The definition of motion is a change in a 3D object's position over time.
    And reiterating discriminatory definitions as well. I showed that definition to be false even in presentism (the shadow), and you didn't counter it, but rather came up with irrelevant comments about its causes.

    I'm only saying there's technically no motion in an eternalist universe. This needn't imply that there's no motion in our universe, only that if there is motion in our universe, then our universe is not (purely) eternalist.
    So you've proven what nobody seems to be able to do, which is to falsify eternalism. Kindly detail some empirical falsification test, Love to hear it.
    So far I have: There is obviously motion. Eternalists are not allowed to use the word, therefore, by language offense, eternalism is false. It doesn't fly because it isn't an empirical falsification.


    The topic has been abandoned altogether, and communication about this side track seems hopelessly mired. I think I will step out at this point.
  • Time travel to the past hypothetically possible?
    You are treating Floyd as a 3D object, not as a 4D object. That is not consistent with eternalism.Luke
    'Floyd at noon' indeed describes a 3D object, yes. Floyd at 1 is a different 3D object, but it is all still Floyd, and the difference in Floyd's location over time is, by definition, motion. It is entirely consitent with B-series language which any eternalist uses without contradiction.

    Is velocity also forbidden then? I mean, velocity in block view is either a rate of change of position over time (generic definition), or it is the slope of the object's worldline (an alternate definition that is not compatible with 3D presentism).

    The constant c apparently has no meaning in physics. Hmm... Somebody ought to tell them that they're all talking bunk.


    The conversation has ceased being about time travel. I apparently cannot discuss an eternalist view with all the restrictions placed on language, all under the guise of 'logic'.
  • Time travel to the past hypothetically possible?
    Presentism is a theory of existence, whereas endurantism is a theory of persistence.

    I think you've misread. I said presentism, not perdurantism.
    Luke
    I did misread it, so thanks.
    I guess I'm not clear on the difference between the two. Both are essentially ontological stances, which is in the end, existence. 'Persisting through time' and 'existing in time' seem to be just different ways of saying the same thing, so perhaps I'm missing an important distinction.

    Huh? No, it wasn't hard to correct you.
    But I never disagreed with the 'corrected' statement.

    You are again assuming that Floyd is a 3D object.
    I never said any such thing, in the context of eternalism. The 3D things are (per the perdurantists) separate 'parts' of the 4D thing. It is the 4D thing said to move (change locations over time), not the parts.

    No 3D part of Floyd changes its temporal or spatial location
    I gave an example where this wasn't true, but I know what you mean. To summarize, by definition, no event that is part of Floyd can be at different coordinates in an inertial coordinate system. It's true of a 0d event, even if not necessarily true of 'parts' consisting of 1-3 dimensions. But motion isn't defined as an event having more than one set of coordinates. It is a difference of location at different times, and Floyd meets that definition.

    which is what a 3D part must do in order to meet the definition of motion.
    To meet your discriminatory definition maybe. Floyd is home at noon and at grandma's at 1. That is motion by the definition. That's how the language is used by an eternalist. The language is serving its purpose, which is to have meaning, and it does so without needing to change the definition from 'change locations over time'.
    The 'over time' part is necessary, because my one hand is at a different location than the other, at one given time. That isn't motion of Floyd. It's a difference in location of parts, sure, but not over time. Extension alone is not usually considered to be motion.

    Any slicing does this.
    — noAxioms
    How?
    Do you understand a 3D cross section of a 4D object? All the events on the arbitrary slice can be assigned the same time coordinate so long as the slice is space-like. Angle the slice a different way and a different set of events (except those events at the intersection of the different slices) are now assigned the same time coordinate. This is essentially a change of reference frame, coupled with relativity of simultaneity, with which I suspect you are not familiar else you'd not be asking that question. A loaf of bread is often the analogy (slicing a 3D object, with time being the long dimension say) along 2D spatial planes, arbitrarily oriented. A slice through a given event (the center of the loaf say) can be angled in many ways and still include that one event, so all the other events are only part of some slices and not part of the others. That's relativity of simultaneity in bakery terms.

    I bring all this up because perdurantists seem to slice Floyd up into 3D disjoint parts, but that can only be done if there is a preferred frame. If arbitrary frames are allowed, 3D cross sections can intersect (be in different locations at 1 given time), and I don't think perdurantists intended that. So without resolution of this issue, they seem to require a preferred frame (absolutism, without the presentism), which violates the relativity theory of which they're presumably in favor. A change in location over frame rotations (instead of over time) is also not considered to be motion by most, but the change in location can be quite large.

    You can probably tell that I'm not impressed with the perdurantist shtick.

    How does Alice4 (Alice1's clone) come into existence?
    Alice1, at the tracks at t=12:00:30 travels back 30 seconds to being there at exactly noon. So Alice1 is at the tracks at noon. Alice2, at t=12:00:30 also selects that same noon event as her destination, so she clones the Alice1 there and the first-noon version of Alice2 (not at the tracks), to create two new clones Alice4 and Alice3 respectively. Alice 2 and 4 are occupying the same space at the tracks simultaneously, and one doesn't survive that.

    Do I have to explain it yet again? I don't know if I can get any more detailed.
  • Time travel to the past hypothetically possible?
    True, but time travel is also not possible under eternalism since nothing moves in a 4D universe.Luke
    Time travel under eternalism is simply any non-timelike worldline, and, if you take the SEP definition, any non-straight worldline. The sort of travel you've been envisioning would be a discontinuous worldline. A continuous but not timelike worldline would have an undefined proper time, meaning it's not clear what the subjective duration of the travel should be, but the external experience of the machine would be much like the description of Putnam in SEP. Funny that his machine sort of has to accelerate to some speed (88 mph just like in BTTF) to make the jump.

    Presentism is a theory of existence, whereas endurantism is a theory of persistence.
    According to the article you linked, both are alternate interpretations of persistence. Despite what various articles might call them, neither is a theory since they both lack any empirical falsification test.

    there is no motion in an eternalist universe, as I have argued.
    And I've shown otherwise, so you're simply wrong. The eternalists use all the same language as do the presentists, but formally, only references to the nonexistent extra thing is what makes a statement meaningless. Motion has meaning under eternalism since a statement such as 'Floyd takes an hour to move from A to B' has meaning.
    Really, why the brutal discrimination here? What purpose is served by your refusal to accept normal usage of language? You seem to seek only to prevent people that hold an alternate view from being able to discuss anything, when clearly the statements have meaning.

    Surely you mean that a 3D part of the 4D object has one location at a given time and a different 3D part of the 4D object has another location at a different time.
    That wasn't so hard, was it?

    You need to explain how two different 3D parts of a 4D object can produce the change required for your definition of motion, when neither of those 3D parts ever changes its temporal or spatial location in the block universe.
    It produces motion by exactly fitting the (not my) definition: Floyd is at one location at one time, and a different location at another. Floyd moves even if what a perdurantist calls his temporal parts do not.

    Okay, but which preferred method of slicing allows for a 3D part of a 4D object to change its temporal or spatial location?
    Any slicing does this. The positing of a preferred way is known as 'absolutism'. The first premise of relativity is that there isn't a preferred way, but it's a premise, meaning relativity isn't proof against a theory that doesn't accept that premise. The slice can be odd shaped. It need not be flat, but it does need to be space-like, else you end up with events that occur out of causal order.

    Alice2 can only clone herself.
    All the Alices are herself, and Alice1 made it across the tracks without crashing. Alice4 dies immediately upon coming into existence, and is the shortest-lived Alice.
    If your convention is that only Alice2 gets cloned, then I suppose Alice4 and Alice1 are just Alice1, who experiences two different fates, a contradiction of identity. X crosses the tracks. X does not cross the tracks. That violates the law of non-contradiction, and the problem is solved by differentiating Alice1 and Alice4.
    It's all a nitpick what names we give them. The scenario was solved. Time travel is super dangerous. Can we move on? There's so many more problems to discover.

    Your scenario, as I now understand it, is that Alice1 time travels backwards and "clones" Alice2, such that Alice1 and (Alice1's younger self) Alice2 now co-exist at the same time. If Alice2 now time travels backwards, then she will clone Alice3 (Alice2's younger self) and Alice2 and Alice3 will co-exist at the same time. Alice1 will no longer exist, just as all the people on the timeline when old Bob departs and time travels backwards no longer exist. That's what it means to overwrite the timeline; the timeline reverts back to its earlier state at the traveller's arrival time, except that that time now also includes the time traveller and their time machine.
    Mostly right. You didn't mention the Alice that collides and dies with Alice2 in that description (so 3 Alices coexisting at once, but two of them dead). The time machines were cloned as well, so there were 4 of those, one truncated away, two crashed into each other, and the only one remaining is the one never used.
  • Time travel to the past hypothetically possible?
    I didn't realise there were two different definitions of 'happens'.Luke
    "To take place, occur" is what I get from a google query. That works fine, since the definition isn't specifically crafted to exclude the undesirables. To exist means 'to have being', to be real. I can be an eternalist (or presentist for that matter) without being a realist, so an event need not exist in order to happen.
    'Exist; has somewhat different meaning in mathematics, e.g. a positive integer is not prime if there exists a positive integer other than itself or 1 that divide the number evenly.

    What is the eternalist definition of 'happens'?
    I could probably craft one that excludes the undesirable presentist view, but doing so wouldn't in any way constitute evidence that a view excluded is wrong.

    presentism holds that only present objects exist.
    Then time travel isn't possible under that definition of presentism since it would constitute travel to some destination that doesn't exist.

    I don't use the term "presentism" to refer to any "4D versions of it".
    I do, because all of the alternate versions still posit a preferred moment in time, which is the fundamental different between any of them and eternalism.

    Objects lack temporal extension under both presentism and endurantism. Both theories face the same problem if there are two or more frames of reference (or "present moments") involved.
    Presentism doesn't face this problem, because only at most one of those frames can be correct, and probably neither are.
    Eternalism doesn't face the problem since the phrase 'present moments' is meaningless.

    The question was basically asking if you are a presentist (endurantist) or an eternalist (perdurantist).
    I try not to hold hard beliefs. I know both, and can discuss either. The purdurantist wording seems silly to me. I've never seen its terminology used in any practical discussion, such as in the science community. And science definitely uses both eternalism (especially in a discussion of cosmology, relativity, physics, chemistry), and presentism (astronomy, climate science, biology, anthropology). I never hear anybody use 'temporal parts' or 'wholly present'. One context uses B-series terminology, and other contexts use A-series.

    The definition of motion is confined to a presentist view, I agree
    No, your definition is thus confined, worded specifically to exclude a view you find undesirable. 'The definition' : 'to change position' isn't so confined.

    An eternalist universe contains 4D objects
    No, a purdurantist universe contains this. Don't confuse the two.
    4D objects are divisible into different/discrete 3D parts
    Each 3D part of a 4D object exists at a different time
    No 3D part of a 4D object exists at more than one time
    A 3D part must exist at more than one time in order to be able to change over time
    No 3D part of a 4D object can change over time
    No 3D part of a 4D object can change its location over time
    Therefore, no 3D part of a 4D object can move, according to the given definition of motion
    It does not follow that the lack of motion of a 3D 'part' implies the 4D object does not meaningfully exhibit motion.. At no point in any of that do you mention that the 4D object has one location at a given time, and a different location at a different time (which is how an eternalist would word it), which is, by definition (not by your definition), motion. The 3D references are perdurantist phrasing, and the argument above is still doesn't demonstrate that the object doesn't move, only that a specific temporal part doesn't, which of course it cannot since it would need time to do the moving.

    You cannot have two temporal slices at the same time.
    Nonsense. That's what a frame change is, slicing through the same point (a given event, which has a specific time) at a different angle, which makes for two very different temporal slices. I take it by this that you're entirely unfamiliar with Minkowskian geometry.

    It is analogous because no 3D part of a 4D object can change its location over time
    — Luke
    Not true actually. You just need to slice it the right way.
    — noAxioms
    Could you explain further?
    If I slice a 4D object across a spatial axis instead of across the time axis, I end up with a 3D object that has one temporal dimension and two spatial dimensions. The location in 2D space changes over time.
    My example would be a car in a drivers-ed parking lot course, sliced through z= half a meter above the lot. That reduces the 4D car to a 3D object that moves over time. It gets weirder if the driving course has hills in it.

    I'm interested in the philosophy of time, and the implications on the different theories of time.
    How it handles collision is critical to identifying the implications. If I don't know how the machine handles targetting an event where there's already something else, then we cannot explore the implications of a trivial situation where that necessarily occurs.

    I've said several times that they both die. Why won't you accept it?
    You change the story several times, so I wasn't sure which you had settled on. OK, so they both die, Alice3 comes upon the death scene and perhaps doesn't decide to add herself to the wreckage, and chooses to miss her important appointment instead. The universe doesn't end (this time).

    Your machine is very dangerous then, since it seems to require one to place a bet that the destination selected is free of anything larger than dust. It might succeed the first few time, but travel to millions of years ago? Due to erosion and plate techtonics, the destination is almost certainly in the middle of bedrock somewhere, or is way in the air, under water, or even in space. Unless the vehicle can deal with those situations, the traveler dies.

    That's one way of looking at it, I guess. But it also overwrites the timeline and deletes the timeline that the traveller departs from. I wouldn't call that cloning.
    There's four Alices,. Sounds like cloning to me.

    The only one being "cloned", or the only one who has two versions of themself in existence at the same time, is the time traveller.
    That was the convention I had initially chosen. We switched to yours. My convention had only three Alices (not four), and everybody else (Alice or otherwise) was an original. In a way your convention is better, because each person (traveler or not) has a unique history. My convention has a given person (the guy mowing his lawn nearby say) multiple histories that play out in different ways, which violates identity rules.

    Where did Alice4 come from?
    Clone of Alice1, made by the travel of Alice2. Alice4 lives but a moment and is gone in the collision with Alice2. Alice2 lives 30 seconds, and dies in collision with Alice4. I did say that Alice1 is the only happy Alice. It sucks to be any of the others.

    Alice1 is still Alice1 after she time travels. She is the original.
    Right. Her travel creates Alice2. Alice1 never time travels again. She lives but 30 more seconds and is truncated into oblivion.
    So it is Alice1 who lands on Alice2 and they die as a result
    No, Alice2 lands on Alice4. Alice1 doesn't land on anybody, which contributes heavily to her being the happy one.

    and then the timeline continues without any Alices
    Well, 1 is gone, 2 and 4 die in a crash, so only Alice3 survives (if she chooses to lay off the button). If she still hits the button (but in a different place than where the wreck is, and for maybe a different jump than 30 seconds, then she can make a whole bunch more dead Alices, herself included, since no actual traveler survives the experience.
  • Time travel to the past hypothetically possible?
    The observation that "those words can be applied to a block view" doesn't make it logically consistent (with eternalism) to do so.Luke
    Totally agree. My usages of 'happens' for instance, in eternalist context, are logically consistent, and many of yours are not. Perhaps you are trying to use the presentist definition of the word in a non-presentist context.

    They all imply motion which, I believe, is the more fundamental difference between the two views.
    Two of the three imply motion. Motion is not the fundamental difference since both have it. I've said repeatedly: the fundamental different is that presentism posits a preferred moment in time, and eternalism doesn't. That, and only that, is the fundamental difference. All the rest just follows.

    it’s all a matter of parts.
    The perdurantist position seems to very much be about parts, yes. That's for the perdurantists to defend. I've posted some inconsistencies I've found with that.

    This is the endurantist view. It is consistent with presentism due to the lack of temporal extension of its objects which are, therefore, not divisible into temporal parts.
    OK, I think I did misread that. The question comes down to then: Is there a difference between somebody claiming to be endurantist and claiming to be presentist? There are several forms of presentism, so perhaps endurantism is but one of them, perhaps 3D presentism, as opposed to growing block, spotlight, and other 4D versions of it.

    Therefore, the phrase "wholly present" is not, as you say, "a reference to all events in the object's worldline".
    Yes, I withdraw that. The concept of a worldline implies 4D spacetime, and 3D presentism does not have meaningful worldlines, but 4D versions of it do still have worldlines.

    I agree that the answer depends on which reference frame is present and so may be considered as ambiguous.
    However, why do you say that presentists don't have this problem?
    Actually, there is no Andromeda paradox under presentism, in any of its forms. Presentism denies both premises of special relativity: 1) Physics is the same in any frame. Well, it isn't. The whole point of presentism is a preferred frame, and all the others are wrong. 2) Speed of light is the same in any frame. Under presentism, that's false. The speed varies depending on which direction it is going, relative to any frame which is one of the 'wrong' ones.
    So with the Andromeda thing, there is only one current moment in Andromeda, and one's choice of frame has nothing to do with it. The motion of any object is irrelevant to which events are simultaneous. The paradox is a non-starter since presentism is an absolutist view. There is no 'relativity' at all.

    Are "you" a 3D object that is wholly present at each time or are "you" a 4D object temporally extended over time?
    You seem to be mixing views in that query, rendering the question meaningless. If you're asking about eternalism, then keep it to those terms. I've never heard an eternalist talk about something being 'wholly present at some time', which seems not even wrong.

    If you're a 4D object then a temporal part of you is home at noon and a different temporal part of you is at grandma's house at 1.
    That is a decent description of movement in perdurantist terms, which I find needlessly complicated. The science community never uses such cumbersome terminology to say something so simple, which is why the 'temporal parts' page was largely educational for me.

    My argument is that the definition of motion as 'a difference of location over time' applies only to 3D objects.
    OK, then your definition is confined to a presentist view. That doesn't mean that a non-presentist must use that definition. The definition I gave works for both, and I've never seen a dictionary restrict the definition to 3D things. In short, my google query says 'move' means to change position. The shadow of a pole moves, and it isn't a 3D thing.

    The 4D object is all "you", but it's not the same temporal part (3D part/object) of you at one time as it is at another time.
    So per the perdurantists that use that sort of language, 'you' change position over time, but the parts don't. It's still you doing the moving. You're just trying to leverage your private definition onto a view that defines the word differently, which of course makes it contradictory. But that's a straw man fallacy.

    Remember that the two views are fundamentally identical except for that one extra premise of an additional entity. So the two views can use all the same language so long as no reference to that additional entity is made (B-series language). If such a reference is made (A-series), then it is a presentist statement only. So saying 'Floyd moves from home to grandma's house over that hour' works just fine in both views because no reference to that additional entity is made.
    I don't know what purpose you think is being served by trying to argue otherwise.

    You still end up with different temporal parts no matter how you slice it
    Yes, but one slice can be at gradmas house and another (at the same time) is not, so I find it to be a problem. The 3D things posited to 'exist at a time' are ambiguous without also positing a preferred frame.

    It is analogous because no 3D part of a 4D object can change its location over time
    Not true actually. You just need to slice it the right way.

    just as no part of a rigid steel bar can change its location along its own length
    This implies that all the points of a steel bar are at the same location at a given time. The bar changes its location over length instead of a change in location over time. This fits the definition of change, if not motion. Other examples of change not over time: The air pressure changes with altitude.

    Just saying...



    Does air die/explode?
    No, but I do if I'm suddenly in the same place as air that wasn't there just before. If the machine is nothing but an air-filled balloon, then suddenly twice the air would be in there, and it might very well explode from the extra pressure.

    It would be no different to moving the time machine to a particular location in normal time.
    No, that is coming from one side, pushing aside what was there. OK, so maybe it pushes stuff aside. In what direction? Does it do it instantly? That would be a nuke explosion. So it takes time, perhaps expanding outward from a point, which will certainly destroy a Delorean inside of which this growing object suddenly appears. But in such a case, the new machine is alive, and any object already there is shoved aside, possibly crushing or exploding it. The tree would not take it well, and the remainder would probably fall and crush the machine that just teleported under it.

    Let's say that whatever happens to the material already present at the target destination if we moved the time machine there in normal time is the same/similar to what would happen if we moved the time machine there via time travel.
    Doesn't work since the form physics is normal motion, say from one side. Where does that start? From how far away does it effectively come? If it comes from a side, then somewhere it has to initiially appear, and not come from even further to the side. So far, the answer is that it teleports in somewhat off-center of target (destroying whatever is there), and then forcibly moving over to the actual target spatial location, possibly pushing/crushing the additional objects that are there, and of course crashing your own machine, since a vehicle collision is what happens when two things move into the same location in normal motion.

    Sorry if I'm ragging on the answer, but I need to know how it actually appears. If the machine pops fully into existence somewhere (off to the side or not), it needs to deal with the material already there. If it starts at a point and expands gradually outward, then that solves the whole expel at infinite-speed problem, but it also destroys anything inside of which the expansion takes place. And if it takes time, how long? Does it slowly grow into existence over a minute? A second? 9 months?

    I don't see understand why you are pressing this point. What difference does it make?
    The Alice story cannot proceed without knowing this. Also the extreme example of setting your machine to go back half a second.

    Surely we can imagine that the time machine can arrive safely
    No we can't. My examples are specifically designed to reduce the odds of safety to zero. I'm finding flaws in the view envisioned, which I thought was the purpose of all these posts. The half-second just is obviously going to lang on the machine that is there. Destroying it isn't such a bad thing in that case, but I need to know if that's what happens. If the jump finds somewhere more (but not completely) 'empty' nearby, would it teleport there instead? That's a different solution than the bang-and-push thing you described before. It results in different problems.

    but let's assume it has the technology to avoid it.
    What does it do to avoid it? Go to the moon instead? NASA would love it if your machine did exactly that. So much effort saved. Who cares that it's a time machine. It's also a space teleporter.

    You seem more concerned about the ramifications of time travel - the end of humanity or the destruction caused by the time machine - than you are with the possibility of time travel.
    But the possibility of time travel, as you describe it, has exactly those ramifications. If you don't want that, then a different model should be assumed.


    According to my convention, Alice1 is the original; the time traveller. Alice2 is the 30-seconds younger version of Alice1 who exists in the past (just as young Bob exists in the past of time traveller old Bob). I cannot see how both:
    (i) Alice1 will time travel back 30 seconds after crossing the tracks; and
    (ii) Alice2 will time travel back 30 seconds, 5 seconds before crossing the tracks.
    Alice 1 has already traveled and will not do so again. Alice2 will travel back when she gets to the track, cloning everybody on that timeline, so I guess Alice1 vanishes as does everybody not in a machine that goes back in time.
    Alice3 is 30 seconds away from the tracks, and has never traveled. Alice4 is at the crossing, a clone of Alice1 that did the first travel. (I neglected to name here Alice4 in my prior description, but by your convention, two new Alices get created when Alice2 goes back. So Alice2 and Alice4 collide at the tracks, and what happens thereafter depends on your collision resolution description that you're reluctant to describe. Alice3 will get to the scene in 25 seconds, and based on what she finds there, she may or may not decide to just wait for the train, or go back more than 30 seconds to avoid the accident scene, or some other choice.

    I don't like your identity convention since it clones everybody in the universe except the occupants of the machine, but I am using your convention above.

    and if Alice2 time travels 5 seconds before crossing the tracks
    Everybody time travels at noon+30 seconds, back to exactly noon. At noon+25 seconds each virgin Alice gets to the tracks and has 5 seconds to assess the situation and decide to go back 30 seconds or not.

    then Alice2 will not proceeed to cross the tracks
    Maybe. She makes it to the crossing too late, hits the button, goes back 30 seconds, and if her collision with Alice4 isn't noticed, she probably considers it mission accomplished and proceeds to cross the tracks just before the gates start coming down. But I don't think the collision will go unnoticed, which likely will effect whether she proceeds across the tracks or not.

    If Alice1 lands on and kills Alice2
    Alice1 is the first to jump, and lands on nobody. She proceeds across and is truncated out of existence when Alice2 pushes her button. Alice1 is the only happy Alice, so it's a shame her life ends so abruptly.
  • Time travel to the past hypothetically possible?
    It is your assumption that events happen (which you differentiate from mere existence) in an eternalist universe which suggests some sort of flow or motion in an eternalist universe.Luke
    It is not an assumption, but rather an observation that those words can be applied to a block view, and that they don't mean that it is an assumption that time itself is what flows or moves.
    Water flows. The wheels on the bus move. The sinking of the Titanic happens in 1912. None of those statements imply a presumption of a preferred moment in time, and that one presumption is the only fundamental difference between the views.

    Perdurantism has temporal extension; endurantism does not.

    Perdurantists believe that ordinary things like animals, boats and planets have temporal parts (things persist by ‘perduring’). Endurantists believe that ordinary things do not have temporal parts; instead, things are wholly present whenever they exist (things persist by ‘enduring’).
    I didn't read it that way. The endurantists statements you make seem to consider objects to have temporal extension (since a reference to 'wholly present is a reference to all events in the object's worldline, and that is, in the absence of a preferred moment presumption, an eternalist stance.
    The endurantist stance, as stated, needs clarification since it seems contradictory. First of all, there is the statement about being present (not absent) when it exists, but 'when it exists' is ambiguous. Consider the Andromeda 'paradox'. Is the en-route invasion of Earth fleet wholly present in 2024 or does it absent, according to endurantists? The answer is ambiguous due to relativity of simultaneity. The presentists don't have this problem with the Andromeda scenario.
    The other contradiction I see:is that I wholly am present in the year 2000, which includes my tonsils, but my tonsils in particular are absent in 2000, so they are both present (as part of something present) and absent in 2000 (as just the tonsils), a contradiction. So as I said, clarification is needed to clean up such examples.

    The science community cares not at all about such distinctions, and the time travel question becomes a scientific one once we have empirical descriptions of how it all works.

    Motion in a block universe is a difference of location over time, just as it is in presentism.
    — noAxioms

    Motion and/or location of what, though?
    Objects of course. I'm at home at noon, and at grandma's house at 1, a different location (relative to the frame of the surface of Earth) over an hour's time.
    If you get anal and take my attempt at the the endurantists wording of the situation, then "Relative to the coordinate system of the surface of Earth in timezone X, the events in my worldline that have the temporal coordinate 'noon' have the same spatial coordinates as 'home', and the events in my worldline that have the temporal coordinate 'at 1' have the same spatial coordinates as 'grandma's house'.
    But that's a mouthful much more easily expressed with "Between noon and 1, I move from home to grandma's house".

    My argument is that the definition of motion as 'a difference of location over time' applies only to 3D objects.
    Well I just applied that definition to a 4D object just above.

    Since each 3D part (of the 4D object) exists at a different time, then no 3D part moves or changes its location over time.
    OK, this is just a refusal to use the typical identity convention, that me at one moment is not the same me a second later, but rather two separate entities. Regardless of a presentist or eternalist stance, if that identity convention is used, then indeed, nothing can move, by definition. There are valid attacks on the usual identity convention, so this can be a reasonable alternate convention. I think I can disassemble any identify convention by choosing the right example, so I don't suggest any one convention is necessarily correct.

    It sort of has all sorts of moral implications, that one cannot be held responsible for something a different entity did yesterday. It's an interesting exercise to argue why that statement is not so much true, but rather meaningless given the assumptions made.

    Another counterargument to the whole 'separate 3D parts' interpretation is that a 3D part is coordinate system dependent. There are different was to slice a 4D worldline into 3D cross sections, and absent a preferred angle of slicing, there are not actually any 3D parts, but rather only utterly separate 0D events that are the 'parts'. The perdurantist stance doesn't seem to get into this, perhaps because the adherents are not really up on the physics from which all these eternalist views sprung in the first place.
    The SEP article on temporal parts seems to mention some of these problems in section 7, but without resolving any of them.

    It would be analogous to part of a steel bar "moving" along its own length; it doesn't happen.
    That usage of 'move' does not conform to the definition given, so no, it isn't analogous.

    I have no idea why you think I never replied to your post from a week ago.
    My bad. Some of the notifications are not coming through. Will try to reply to parts not covered since.


    How would air, dust or bugs at the destination prevent time travel?
    I asked for how you envision interaction with material already present at the target destination. Your answer was simply 'die/explode'. So perhaps the answer needs to be changed. Maybe it handles air better, by what, pushing it aside first? Absorbing it (which probably covers 'die' pretty well)? The answer you gave does not imply that it simply replaces what was there with a new state (terminator style, except with electrical effects preceding).
    So if explode/die is the wrong answer, then what is the actual answer? If air is treated differently than other material, where is the line drawn, and how about the bugs, which are definitely not air? How about the tree I mentioned?

    If the machine can time travel, then it can probably find a safe place to arrive.
    That's a different answer. So it assesses the target, and selects somewhere close? Does it have a limit as to how far (both spatially and temporally) it is willing to look for a satisfactory point in which to insert itself? What does it do with the stuff that is already at the selected point?
    Alice hits the button to go back 30 seconds and finds herself on the tracks with the gates already down (just like in BTTF) and with a train 3 meters away. Hey, it was the nearest available spot...

    I need to know the rules so I can illustrate the contradictions that result from those rules. We've not even attempted everybody having such a machine yet. I can't imagine how many questions it's going to take to get a clear model of that, but it probably won't happen because the machine you envision erases history, so in very short order, all those other machines will be erased from history by the person who travels backwards the furthest.

    You've lost me here. There are three Alices?
    Two travel events (both by younger Alice, traveling for the first time ever), each one making a clone, so yes, three of them. Did you forget the machine makes clones?

    Alice goes back 30 seconds. Okay. Then there is also an "Alice behind". Is she the same Alice as the one who just went back 30 seconds?
    Depends on your identity convention. Which do you consider to be the original in the just-truncated history, the one that traveled, or the younger one that has not, but is about to? When she does, at noon there are two or three Alices, depending on the microsecond timing. If the 2nd destination event happens ever so slightly sooner than noon, it erases the noon event of the appearance of the Alice that makes it across the tracks, and there still remain two Alices, the one that just appears, and the one 30 seconds back that is approaching the crossing and is going to hit the button in 30 seconds.
    If the timing is the other way (which it must be eventually), the 2nd travel event lands exactly on the first one, and the whole explode/die thing occurs, leaving only the younger Alice who will get to the explosion scene 25 seconds after noon.

    Apparently not, since those two Alices die after one lands on the other. So, where did "Alice behind" come from?
    She is always there. Nobody traveled back far enough to erase her from history. She's the one that has never traveled before, and is late for her appointment.

    However, now a third Alice approaches the tracks to find the wreck of the collision that killed the other two Alices.
    It seems you convention is to consider the traveler to the original, and the other in the timeline to be the clones.
    So in the Bob thing, the original Bob goes back and kills his younger clone, who is not Bob, but rather clone-Bob.
    I had been using a different convention, but which one used doesn't matter except when we assign names.

    Where did third Alice come from? Was it only the first Alice who time travelled?
    Using your convention, the original goes back (Alice1), who crosses the tracks,. Alice2 is 30 a clone, 30 seconds younger, and will get to the track in 25 seconds and will decide to go back 30 seconds to make it across. Alice2 goes back to noon, explodes and dies in a collision with identically aged Alice1 who also appears just there, and Alice3 (30 seconds younger than 1 and 2) will get there in 25 seconds.

    If these are different people then why did you call them all Alice? This is very confusing.
    They are all Alice, but I put numbers on them to keep track of the clones. I used your convention.


    From last week:

    Much of the confusion early in that post is my using a different identity convention, where I consider, in a timeline resulting from a travel destination event, that the traveler is the original and those pre-existing in the timeline are the orginals. The story as reworded above utilizes the opposite convention where the traveler is designated as the original.

    Your argument is supposedly that my presentist model entails a blank future universe.
    If it doesn't wait for the destination to be written, then yes, it is blank. If it just makes up a state to write into that blank space, then fine, it puts something there, all very BTTF. Nobody can tell anything is weird except those who witness (or better, catch on video) the appearance of the time machine out of nowhere.

    I could say that the future has a definite physical existence prior to the time travel
    Your model had truncation. This statement seems in contradiction with that term, which sort of implies that when the present is moved back to 1990, the written state of things between 1990 and 2024 is reverted back to a blank state. Now you suggest otherwise. All very self contradictory. Perhaps more clarification is needed as to what exactly happens to the 34 years between when the present is moved back to 1990.

    You say you're not necessarily a presentist, but you've been describing something that matches only growing-block theory, and matches nothing else. This more recent statement is more like moving-spotlight, where 'the future' is sort of written (exists), but is not yet at the preferred moment.

    I think many works of fiction depict time travel as I depict it in my model, where the time traveller travels to, and inserts themselves into, a time they have never visited before (as a time traveller). For example, Marty McFly was never in 1955 prior to his first time travel event, and his time travel results in changes to the 1985 he departed (i.e. he overwrites the timeline).
    And encounters a slow version of the grandfather paradox where he is threatened with nonexistence by changing the circumstances leading to his birth, a different story than the one you tell. Anyway, that story is full of contradictions, and it doesn't explicitly call out the interpretation of time it is using. The movie probably contradicts any valid interpretation of time.

    Presumably backwards time travel works differently. Why should the machine have to wait in forwards time travel if it is not required to wait in backwards time travel?
    In a growing block model, the past exists but the future does not, but will eventually. Hence the wait. In a moving spotlight model, both exist, and it is merely a matter of 1, moving the spotlight, and 2, creating a destination state that is compatible with the identity convention of choice. In raw presentism, backwards time travel is impossible because the destination doesn't exist, and never will again. Under eternalism, a branching model in Hilbert space is probably the best, but world creation is not really time travel without a simultaneity convention between separate worlds.


    Why do the events happen in a sequence when they don't exist in a sequence? That is, events do not flow into and out of existence sequentially in an eternalist universe, like they do in a presentist universe. So, why do they happen sequentially in an eternalist universe?
    Putting them in a sequence is a choice, a natural choice, as I've illustrated. I can create a series of pictures that a child can order in apparent causal order, not necessarily in the order in which the pictures were drawn.

    You seemed to be arguing that there are no events before the big bang even though there are times before the big bang,
    I don't argue for meaningful time 'before the big bang', given a realist definition of the universe as 'all there is', there would probably be more than what is accounted for by just the spacetime that we know. The ability to temporally order the other parts is likely meaningless, so different language is needed to discuss such things.
  • Time travel to the past hypothetically possible?
    What makes you think I'm ignorant of the theory of eternalism?Luke
    It's just that every attempt at describing things in eternalist terms still adds references to flow or other implications of a special moment in time.

    You do seem to be more familiar with the glossary as used in the philosophy sites. I come from more of a physics background where such terms and distinctions are not important. I've never heard a physicist refer to a 3D part of a 4D object, but apparently SEP is full of that sort of thing, and you linking to those sites has helped me see what the language is all about.

    For someone who regularly accuses me of ignorance of concepts in the philosophy of time, I find it amusing that you are obviously unfamiliar with the concept of temporal parts.
    It seems I am.
    The SEP site describes spatial parts that are extended (hand, feet and such), but when it comes to temporal parts, it seems not to allow any extension to them, which seems an inconsistent use of the term 'parts' to me.
    The article is supposed to be describing a form of eternalism, but it still makes plenty of references to 'the present, past, and future', which begs a different view.

    Physics doesn't seem to care about the distinction between perdurantism and endurantism, and the difference seems merely one of language. The views don't seem actually different in any physical way, so I couldn't really say which of the two I'd side with if I had to choose one.
    It seems one finds meaning to the question of 'does a 1947 event exist in 2047?', and the other view does not find the question meaningful as worded.

    Before your break, we were discussing whether events can happen (or be happening) in eternalism, so I don't consider a further discussion of the implications of eternalism to be a side topic.
    This is also mostly a choice of how to use the language, but the tense 'can be happening' in the absence of an explicit time, constitutes an implicit reference to the present, and such references should be avoided. I've said this repeatedly.

    You appeared to be arguing that eternalism is the only theory that can make sense of time travel.
    Not at all, but it treats it differently. Different interpretations work in one interpretation or the other, but most not in both.

    Besides, you completely ignored my argument against motion in an eternalist universe, just as prior to your break, you never replied to my argument that Alice0 cannot be the original Alice.
    Motion in a block universe is a difference of location over time, just as it is in presentism. What was you argument against that again? Do you deny this definition, or deny that it applies to either view?

    As for which Alice is the original, I simply chose a convention. I never argued that a different convention was necessarily wrong. The Alice story can be told using either convention.
    Also, it was you that took the break, never replying to anything from my post a week ago.

    Yes, if the car/person jumps to the same location as another car/person then they would all die/explode/cause a black hole/etc.
    Then time travel is mostly impossible the way you envision it since there is always something (air, dust, bugs, trees, whatever) at the destination, unless one chooses to materialize in deep space, and none of your scenarios do that. But here you suddenly suggest that materialization at a location that already has something results in the destruction of the machine and whatever was there before.

    If it materialized in deep space, the machine would be wonderfully useful for budget space travel. Other worlds could be populated effortlessly, a task currently not feasible.

    So Alice goes back 30 seconds, crosses the track, and the Alice behind travels back 30 seconds later and lands on the first traveling Alice, and both traveling Alices die, leaving just the younger Alice approaching the tracks, who finds the wreckage of the collision there, and thinks twice about adding herself to the heap. Problem solved, but Alice misses her interview appointment and doesn't land the desperately needed job,.
  • Time travel to the past hypothetically possible?
    Yes, because most people are not physicists that understand relativity theory. Hence, "commonly held".Luke
    Alright, but when in a discussion where the implications of a specific theory (or its alternatives) are very relevant, coming into the discussion in ignorance of that theory doesn't put you in a position where your view can be coherently argued.
    For instance, you seem to be able to discuss black holes probably because you've heard the term on pop-science sites or the news or whatever, but only Einstein's theory predicts them. They cannot exist under presentism of any kind. So the commonly held view is also self-contradictory, which is simply not a concern of the average guy on the street. Probably 99.9% of everybody holds views somewhere that are mutually in contradiction. But most of those people don't argue on forums for the consistency of the specific points that are in contradiction with each other.

    3D parts of the 4D object.
    I see what you're saying. It's a funny way of putting it, but I suppose so. I would have called them cross sections instead of 'parts'.


    All this is a side topic. We need to make progress since almost none is being made in a 200+ post topic.
    None of the post was about time travel, and your rules continue to be evasive.
    Suppose I take my (stationary) machine and go back half a second. There's obviously a machine sitting at the targeted destination, so where do we materialize? Does the machine of 1/2 second ago get trod upon and destroyed, both machines destroyed (car crash style), or does it find somewhere/somewhen else to materialize? What's the rule here?
    I really couldn't make progress on the Alice example without knowing how you envision this.