Comments

  • What are the "Ordinary Language Philosphy" solutions to common philosophical problems?


    Examples that come to my mind are many of the philosophical problems concerning “nothing” and/or “nothingness”:

    If someone asks me if there's something in my room, and I reply: “there ain't nothing in my room”, in ordinary life the phrase has a perfectly clear meaning, and questions about “nothing” or “nothingness” never even arise.

    But a logician or metaphysician could be quite puzzled by this, when analyzing the phrase he may think:

    1.There ain't nothing in my room= There isn't nothing in my room= There is not(not something) in my room= It is not the case that there is (not something) in my room.

    2. Either there is not something in my room, or there is something in my room.

    3. Therefore, the phrase “There ain't nothing in my room” means “There is something in my room”, which is exactly the opposite of what I meant to say.

    And so the metaphysician could ask: How can a phrase be understood as the exact opposite of what it actually means (according to its logical structure)? And he could then go on by saying that “nothing” is actually “something”, and develop a complex metaphysical system from that premise, or by looking for the “true/correct” analysis of the meaning of that sentence.

    In ordinary language philosophy, like I said, questions like that don't even arise, they are “bewitchments by language”.

    If we follow the late Wittgenstein's maxim that the meaning of a word (or of a sentence) is its use in a particular language game, then all that matters is that everybody understands what the phrase means in the context of ordinary life activities, and have no need of analyzing the logical structure of the phrase to do so.
  • The death paradox


    When already died (I guess you mean dead?), saying the he cannot die, sounds like some tautology or meaningless proposition to make.Corvus

    It's not meaningless (and it's not a tautology either, since it's not logically impossible for someone to come back to life, merely physically impossible as far as we know), the proposition: “When someone is dead, he cannot die (again)” is clearly true, since if someone was dead and then died, he would have died twice, which is impossible.

    At least, that seems to be what Sextus is saying.

    Not sure about not legitimate - never came across that term in the Logic books.Corvus

    “Not legitimate” as in unreasonable.
  • The death paradox


    When socrates died, he has already died, so the premise that socrates couldn't have died when he died seems invalid.Corvus

    A premise can't be valid or invalid, only an argument can. A premise can only be true, false or meaningless.

    If you say that premise is false, what's your response to this then?:

    nor did he die when he was dead, since he would have died twice. — Sextus Empiricus


    When someone is already dead, it is not valid to declare, he cannot die.Corvus

    What do you mean by “not valid” here? I guess you mean illegitimate?

    But why isn't it legitimate? Isn't it correct to say that a living thing can only die once? Because the only way someone could die twice would be if they died, then came back to life, and then died again, which is surely impossible right?
  • The death paradox


    Is the mooted standard Metre Rule, the one in Paris from which all others are copied, a metre long? How could you tell - by measuring it against itself? But that's not performing a measurement.Banno

    I didn't notice this post before, and I confess that I'm a little puzzled as to what you are getting at here. Could you elaborate a bit on how this is related to what Sextus said?
  • The death paradox
    Sorry about the huge delay of my response. I just saw your reply just now.Alkis Piskas

    @Trinidad was banned, so I'm afraid he/she won't be able to respond to your post.
  • The Postmodern era: Did it happen?
    Did the 'postmodern condition' actually happen?Kenosha Kid


    I think it can be summarized in this statement: postmodernism is (philosophical) scepticism on drugs.

    I am not thinking of people like Michel Foucault, who actually had interesting ideas, but rather the authors criticised by Sokal and Bricmont in their “Fashionable Nonsense” (Lacan, Derrida, Irigaray,...)

    Basically, I have not found in those postmodern authors anything that was not found already in philosophers like Sextus Empiricus and David Hume, who also expressed their ideas in a clear, non pedantic, non trivial and much more profound way.
  • A Counterexample to Modus Ponens


    At a point before the election, with 'win's understood as 'will win', then R v A is true.

    At a point after the election, with 'wins' understood as 'won', then R v A is true.
    TonesInDeepFreeze

    I was refering to Bartricks' fallacious argument, not to the OP's.
  • A Counterexample to Modus Ponens


    Premise 2 is false= ¬p

    1. p→¬p means: ¬p v ¬p, which is ¬p.
    2. p
    3. Therefore ¬p.

    Obviously, if you have both p and ¬p as premises you can conclude anything you want, since anything follows from a contradiction.

    The implication p→¬p is only true if ¬p is true. So if 2 is true, 1 is false, and you can't infer ¬p using modus ponens.

    See:

    It's just a case of the so called “paradoxes of material implication”.Amalac
  • A Counterexample to Modus Ponens


    p: a Republican wins the election.
    q: if it's not Reagan who wins, it will be Anderson (q = r→s)

    r→s is equivalent to ¬r v s, so q should be interpreted as: either Reagan wins or Anderson wins.

    Since Reagan won, q is true, since one of the components of the disjunction is true.

    Before Reagan won, if it was possible that Carter could have won, they couldn't have known whether q is true or not.

    But, since p is true , q is true, and p→q is true, modus ponens leads to a true conclusion from true premises.

    It's just a case of the so called “paradoxes of material implication”.
  • A question concerning formal modal logic


    That is incorrect. To accept a proof does not require accepting the truth of the premises.TonesInDeepFreeze

    Oh, well if that's what you meant then obviously, if one of the premises is the Law of Contradiction or assumes the Law of Contradiction, the sceptic can just grant the validity of the proof while denying both that premise and the conclusion. He would say: “yes, obviously if the Law of Contradiction is true, then the Law of Contradiction is true, but I'm questioning the claim that the Law of Contradiction is true, not the implication”.


    It only proves G is true if all the axioms used in the proof are true. So, since G is an axiom used in the proof, if it is false, then, though we have proved G, we have not proved that G is true.TonesInDeepFreeze

    Right, so the same thing that you say about G, one could say about the LNC: we have proved the LNC, but we have not proved that the LNC is true. The sceptic wants a proof that the LNC is true, that's the proof I was refering to.

    However, it seems you say that unlike for G's truth, there actually is a proof that the LNC is true (not merely a proof of the LNC), is that right? It seems it's the one you are refering to here:

    No, it's not just an assertion. It's a theorem about propositional logic. And it is reducible, in a sense, to a theorem about Boolean algebra. And its proof is reducible to finitary operations, which are reducible to auditing the execution of an algorithm. So (heuristically speaking) we may say that at the root of the question is ability to audit the execution of an algorithm. Of course, it's hard to imagine such an ability in a person who was so delusional that they claimed to witness '0' and '1' written in the same space when only one of them was written in that space. But that is not the same as going all the way back up the chain of reductions I just described to say that LNC must be an axiom.TonesInDeepFreeze

    I recommend 'Logic: Techniques Of Formal Reasoning' by Kalish, Montague, and Mar. Within about a chapter you could assign yourself the easy exercise of deriving LNC in the natural deduction system there.TonesInDeepFreeze

    Thanks for the recommendation, I'll read when I have the time (if I can find the book, that is).
  • Abortion


    If you do nothing to the baby, it exists.TheMadFool

    The baby is not the fetus. You mean to say: if you do nothing to the fetus, then in the future it will become a baby.

    In order for me to choose between doing something to the baby or not, it must already exist, and in that case obviously if I do nothing and he is fortunate, he will continue to live. But it doesn't follow from that, that I should do the same with a 2 week old fetus.

    Ergo, if it doesn't exist, you did something to the baby!TheMadFool

    No, you can't do anything to what does not and did not exist.
  • Abortion


    Crying, wet and pouting lips searching for the mother's breast for milk.TheMadFool

    In the future, if and only if the woman decides not to abort, not when the fetus is 2 weeks old. But the question is: does anything happen to the actual baby when the fetus is 2 weeks old? Answer: no, because there is no actual baby at that moment.

    Scenario 2:

    Fetus aborted. No crying, no wetness, no pouting, in short no actual baby
    TheMadFool

    Again, in the future that's true, if and only if the mother decides to abort, but also when the fetus is 2 weeks old, and the question is: does anything happen to the actual baby when the fetus is 2 weeks old? Answer: no, because there is no actual baby at that moment.

    If nothing was done to an actual baby where is the baby?TheMadFool

    When the fetus is 2 weeks old, it doesn't have to be anywhere because, like I said, there is no actual baby at that time, regardless of whether you choose to abort the fetus or not.


    Now, if the question is: does something happen to the actual baby when he is 1 year old? then the question already assumes that the 2 weeks old fetus wasn't aborted, and in that case obviously many things happen to him, but not those that happened to the fetus in the past (since he is not the fetus, just as he is not the stardust that had the potentiality to become him). If the fetus was aborted, then the question is a loaded question, or one that would have to be answered with: nothing happens to the actual 1 year old baby, because there is no actual 1 year old baby.
  • Abortion


    Suppose all this happens when the fetus is, say, 2 weeks old.

    Then in scenario 1, if you do nothing to the fetus, then at that moment nothing happened to the actual baby, because there is no actual baby.

    In scenario 2, if you abort the fetus, then at that moment nothing happened to the actual baby, because there is no actual baby.

    In both scenarios, things happen only to the fetus. That's why the only way to make sense of that argument is to say that the fetus and the baby are the exact same thing, which is to say: that potentiality and actuality are the same thing, which is obviously absurd.

    Also, emoticons are not a way to avoid justifying why, according to you, something would happen to the actual baby (which does not exist) in either of those scenarios.
  • Abortion


    Scenario 2

    X aborts the fetus. X doesn't give birth to the baby

    X did something to the fetus. Something happened to the baby
    TheMadFool

    Nothing happened to the baby, there is no baby to begin with. It's like if you said the present king of France is sleeping: it's not the case that he is sleeping, because he doesn't exist to begin with.

    In other words, it's not possible that X can do something to the fetus & X can have a baby (that's what abortion is all about).TheMadFool

    So?

    If you say that doing something to the fetus does nothing to the baby then this should be possible: X does something to the fetus & X can have a baby (like X did something to the tooth and X can have a baby). This is impossible.TheMadFool

    No, this is the same non-sequitur/ straw man as before.

    Ergo, To do something to the fetus implies to do something to the baby.TheMadFool

    ...and to do something to the seed implies to do something to the tree that the seed could become (do you really not see the problem with this?)

    Not to do something to the baby implies not to do something to the fetus.TheMadFool

    False, that's like saying: not to do something to the tree implies not to do something to the seed. But obviously just because I don't put the tree in my palm (because the tree doesn't exist to begin with), that doesn't mean that I can't put the seed in my palm.
  • Abortion


    Goodness gracious...

    I mean that this:
    I can't do anything to the actual baby if I have an abortion i.e. if I destroy the fetus.TheMadFool

    Does not mean the same as, nor implies:

    an actual baby should be born even if I destroy the fetus.TheMadFool

    It also does not mean that:

    So, if I destroy the fetus, I destroy the baby. That's what I meant from the get go.TheMadFool

    Also, I'm still waiting for your response to the argument that cleaning scattered seeds is deforestation.
  • Abortion
    That means an actual baby should be born even if I destroy the fetus.TheMadFool

    No, that doesn't mean that at all (if you mean the same baby that the destroyed fetus would have become).
  • Abortion


    Non sequitur/ straw man, that's not another way of saying that at all.

    Obviously, if a woman wants to have a baby, she must not destroy the fetus that she plans on having become a baby (the baby that the fetus will become), but that doesn't mean that destroying the fetus has effects on some non-existent baby.

    Anyway, here's a consecuence of your “argument”:

    1. Doing something to the potential tree (seed) implies doing something to the actual tree.

    2. If 1 were false, destroying the seed should have no effect on the tree, which is just another way of saying that you could destroy the seed and still grow a tree (the tree that the seed would have become if it hadn't been destroyed).

    3. Therefore, since 2 is preposterous, cleaning scattered seeds in a garden is deforesting, and should be punished in the same way as burning the same number of trees.
    Amalac
  • Abortion


    1. Doing something to the potential baby (fetus) implies doing something to the actual baby.TheMadFool

    1. You can't do anything to what doesn't exist (the actual baby doesn't exist, only the potential baby does).

    If 1 were false, destroying the fetus should have no effect on the babyTheMadFool

    Of course, destroying the fetus can have no effect on what doesn't exist, nor can anything else. The baby doesn't exist.

    which is just another way of saying you could destroy the fetus and still give birth to the baby.TheMadFool

    Non sequitur/ straw man, that's not another way of saying that at all.

    Obviously, if a woman wants to have a baby, she must not destroy the fetus that she plans on having become a baby (the baby that the fetus will become), but that doesn't mean that destroying the fetus has effects on some non-existent baby.

    Anyway, here's a consecuence of your “argument”:

    1. Doing something to the potential tree (seed) implies doing something to the actual tree.

    2. If 1 were false, destroying the seed should have no effect on the tree, which is just another way of saying that you could destroy the seed and still grow a tree (the tree that the seed would have become if it hadn't been destroyed).

    3. Therefore, since 2 is preposterous, cleansing a garden of scattered seeds is deforesting, and should be punished in the same way as burning the same number of trees.
  • Abortion


    Destroying the fetus, destroys the baby, no?TheMadFool

    No, that’s like saying that destroying the seed destroys the tree it would have become otherwise. Once again, you can’t destroy or kill what doesn’t exist. Also, nobody would on that ground infer that crushing seeds is the same as deforesting.

    Unless you are committing the fallacy of equivocation, in which case I can translate your sentence into one that perhaps makes more sense: if you destroy the fetus, the baby it might have become won’t exist in the future. Well yes, but so what? The burden of proof is on you to show why that implies that it is morally wrong to kill the fetus, because I don’t see how that follows at all.

    And if you are going to say that anything that is potentially a baby should be treated just like a baby, then is killing spermatozoa (masturbating) murder as well?

    Likewise, I could argue in the same fashion: if you destroy the seed, the tree it might have become won’t exist in the future, therefore crushing seeds or cleansing your garden of scattered seeds is deforesting. Are you willing to accept that? If not, you must agree that arguments with that logical structure are not valid.

    Remember, a woman's concern is the actual babyTheMadFool

    So what? It does not follow that a fetus (potential baby) is a baby from that statement, her intentions for killing the fetus are wholly irrelevant to the question whether a fetus is or should be treated like a baby or not.

    To do something about the actual baby, the woman does something to the potential babyTheMadFool

    Again, that does not mean that the potential baby is the same thing as the actual baby. Plus the actual baby doesn’t exist.


    It's crystal clear to me as it should be to you.TheMadFool

    It’s crystal clear to me that a seed is not a tree, because a potential tree is not a tree in actu.
    It’s crystal clear to me that a fetus is not a baby, because a potential baby is not a baby in actu.
  • A question concerning formal modal logic


    What I was aiming at is that logic is the handmaid of what is the case. One of the things we do with language is that when it doesn't seem to show us what is the case we change what we are saying.

    DO you agree with that?
    Banno

    Of course I do agree that we should make language fit what we know about reality and not the other way around. It may happen that, for example, we were wrong in thinking some object had a certain characteristic that we labeled X, because we made a wrong inference based on misleading or insufficient evidence, and later learned that that inference was wrong, and that the characteristics of that object were such that it didn’t fit in the definition of X, and in that case we would no longer say that it has that characteristic X.

    But anyway, how does that lead to the claim that it is not possible to prove the existence of anything a priori, that is: that no analytic proposition can also be existential in its content? I suppose you may say that such a proposition would try to make reality fit into language rather than the other way around, but supposing God did exist, that would not be the case, we would in that case make language fit into reality.
  • A question concerning formal modal logic


    That's a very silly question. I don't know it, since it is not the case, and I can't know that which is not the case. Are you trolling me?

    Or maybe you meant to type: How do you know that they also don't prove it is not a theorem?
    TonesInDeepFreeze

    Yes, that was my bad, I'm too tired from work, I wrote too quickly and forgot to add that other negation, I'll try writing more slowly now. (Also english is not my mother tongue so please have mercy on me).

    That's one notion. But another definition of 'axiom' is purely syntactical.TonesInDeepFreeze

    Let's start here, what's this purely syntactical definition of “axiom” you speak of?

    The proofs can be mechanically audited whether the auditer knows of LNC as an axiom or not. Indeed, even for everyday reasoning, probably most people haven't even heard of LNC, especially the notion of it is an axiom. And that does not contradict that good reasoning (other than dialethistic) conforms to LNC and sometimes uses it - either as an explicit or implicit principle.TonesInDeepFreeze

    But they must still accept it implicitly without proof (that's what I mean by “accept it as an axiom”). Of course we don't make all our inferences explicit, but we still implicitly infer many things, which require us to accept some propositions as true without proof, among which is the Law of Contradiction. As Aristotle said: It is utterly impossible to prove everything.

    Someone who doubted that the Law of Contradiction was true, would not accept any proof that assumed, without proof, that the Law of Contradiction is true, he will demand that you prove it without having it as an axiom or assuming its truth in any way, since he won't accept circular arguments.

    In one sense, it is trivially true that if you have the Law as an axiom, then you can prove that the Law is true. Likewise, if I have “God exists” as an axiom, I can prove that God exists.

    Or if someone asked you to prove that 5=5, and you told them: “If you accept that A=A is true for any number you substitute for A, then it necessarily follows that 5=5” he may reply: “And why should I accept that A=A?”, and so it becomes clear that you can't convince him that 5=5. The same thing happens with the Law of Contradiction sceptic, you also can't convince them that the Law is true.

    It is fine to have it as a logical axiom, since it is logically true. Sceptics should learn that it is logically true.TonesInDeepFreeze

    That's just an assertion, the LNC sceptic will demand a proof for it. They want to learn why it's true.

    First, it is possible for one to assert and deny a proposition. And it is even ubiquitous that people assert propositions that are inconsistent with other propositions. So probably what you mean is that it is not possible to be correct while both asserting and denying a proposition. Then your question seems to be how do we know that contradictions are not the case. But the question of how we know things is different from the question of what axioms we choose. We may know that a proposition is true by reasoning from different axioms that each yield the proposition as a theorem. It is not required that LNC be one of the axioms. If, as we ordinarily do, we require a system that is complete in the sense of proving all validities then it is only required that LNC at least be a theorem even if not an axiom.TonesInDeepFreeze

    Could you please show me a proof of the Law of Contradiction that didn't have it as an axiom, and didn't assume that it is true,without proof, in any way?
  • A question concerning formal modal logic


    I think this because logic is about what we can say, and not about the way things areBanno

    The problem is that I don't agree with this statement: I think logic is about what we can say, but also about the way things are (in the sense in which Russell also holds this in that last statement of his that I quoted previously).

    So how do you explain this disagreement when we seem to agree about the rest? That's what's got me a little puzzled, unless you changed your mind.
  • A question concerning formal modal logic


    Well, I thought you held that the Law of Contradiction was only a rule of language, but now you are saying that it does reflect how the world is.

    What I don't understand is how that's consistent with this earlier statement of yours:

    I think this because logic is about what we can say, and not about the way things are.Banno
  • A question concerning formal modal logic


    Ok, but like I said, Russell doesn't disagree and neither do I:

    The belief in the law of contradiction is a belief about things, not only about thoughts.
    — Russell

    His “only” implies that he holds that the belief in the Law of Contradiction is both about thoughts and about things.
    Amalac
  • A question concerning formal modal logic
    Edit: sorry, got the quotes mixed up at first, since I'm writing from my phone's half broken screen I didn't notice.

    But no difference between Amalac and Amalac.Banno

    Obviously not, but what exactly did you mean then? What point were you trying to get across here? :

    Even as Amalac is both a word and you.Banno
  • A question concerning formal modal logic


    They prove it as a theorem. Of course, our motivation for the system would include proving it as a theorem.TonesInDeepFreeze

    How do you know that (Edit: sorry, missed adding: “it's not the case that” here, I'm very tired from work) they also don't prove it as a theorem? By accepting the Law of Contradiction as an axiom? Then you are agreeing with me: It cannot be proven so it must be assumed as an axiom. By definition, axioms are accepted as true without proof. So the question is: Why should a LNC sceptic accept that axiom in the first place?

    My point is that your proofs only work if someone accepts the Law as an axiom, if they don't, then your “proofs” are circular.

    Talk meaningfully" is a large and undefined rubric.TonesInDeepFreeze

    Without assuming the Law as true without proof, for all I know you may have both asserted and denied everything you've said this far. That's what I mean.
  • A question concerning formal modal logic


    Not all proofs use the law. Indeed, the law is not even usually one of the logical axioms.TonesInDeepFreeze

    They don't assert the Law of Contradiction explicitly, but they must assume that it is certain implicitly, otherwise it is not even possible to talk meaningfully, as Aristotle pointed out.

    (1) Trivial. If the law is an axiom then it also provable by the rule of putting an axiom on a line.TonesInDeepFreeze

    Only if you assume that it is not also the case that the Law is not provable by the rule of putting an axiom on a line, which requires the Law of Contradiction and makes the “proof” circular. It certainly would not convince a LNC sceptic.

    And the same applies for the rest of the “proofs”.
  • A question concerning formal modal logic


    Perhaps it would help to think of it like this: Russell supposes that either the law of noncontradiction is a fact int he world or a figment of language.Banno

    I don't think so, here he says:

    The belief in the law of contradiction is a belief about things, not only about thoughts. — Russell

    His “only” implies that he holds that the belief in the Law of Contradiction is both about thoughts and about things.


    Even as Amalac is both a word and you.Banno

    A word is not the same thing as that to which the word refers.

    So if Amalac, in the following sentence, means “the word Amalac” then I am not Amalac.

    If it means “the person writing this right now”, then I am Amalac.

    The only way you can assert that “Amalac” is both a person and a word is through either denying the Law of Contradiction, or through the fallacy of equivocation.
  • A question concerning formal modal logic


    Well yes, since all proofs assume the Law, it itself cannot be proven, as Aristotle pointed out.

    But it's just blindingly obvious, is it not? I mean, if we can't be certain about that, we can't be certain about anything.
  • A question concerning formal modal logic


    But perhaps the best way to proceed would be for you to set out exactly what you think Russell's argument is in the piece you quote; because I don't see an argument thereBanno

    There is an argument, it's just brief:

    1. Either the Law of Contradiction states merely what we must believe, and what we can't believe, or it also asserts how the world necessarily is and must continue to be like.

    2. It is impossible for the Law of Contradiction to
    ever be false (interpreted as an assertion about the world, and not merely about our thoughts).

    3. If the Law of Contradiction merely stated that we can't help believing that a thing cannot have a property X and a property ¬X at the same time and in the same sense, then the Law could be false in spite of the fact that we can't help believing in it, thus it is possible that the Law of Contradiction (in the sense in which it is applicable to the world) is false.

    4. 3 contradicts 2.

    5. Therefore, the Law of Contradiction must be a fact about the world. ( From 1, 2, 3 and 4)
  • A question concerning formal modal logic


    But doesn't that mean that the Law of Contradiction reflects some kind of a priori, given structure of the world, such that the world must always follow that Law, and doesn't merely stablish a rule of grammar or a statement about what we must believe?

    Do you disagree with any of this?:

    When we have seen that a tree is a beech, we do not need to look again in order to ascertain whether it is also not a beech; thought alone makes us know that this is impossible. But the conclusion that the law of contradiction is a law of thought is nevertheless erroneous. What we believe, when we believe the law of contradiction, is not that the mind is so made that it must believe the law of contradiction. This belief is a subsequent result of psychological reflection, which presupposes the belief in the law of contradiction. The belief in the law of contradiction is a belief about things, not only about thoughts. It is not, e.g., the belief that if we think a certain tree is a beech, we cannot at the same time think that it is not a beech; it is the belief that if the tree is a beech, it cannot at the same time be not a beech. Thus the law of contradiction is about things, and not merely about thoughts; and although belief in the law of contradiction is a thought, the law of contradiction itself is not a thought, but a fact concerning the things in the world. If this, which we believe when we believe the law of contradiction, were not true of the things in the world, the fact that we were compelled to think it true would not save the law of contradiction from being false; and this shows that the law is not a law of thought. — Russell
  • Why are Stupid people happier than Smart people?


    I think you might like this short story of Voltaire's (The Story of the Good Brahmin):



    (I'm also using this chance to get more people to know of Akizur's great but little known channel).

    I think the question whether wisdom is more valuable than happiness is a very important one, and one that I would unhesitatingly answer by saying that happiness is more valuable.

    The example I like to use is that of Georg Friederich Haendel, a composer of the utmost genius, but compared to someone like E.M. Cioran for instance, he was very ignorant in my opinion.

    Yet I'd argue that Haendel was far happier than Cioran was, and Cioran is indeed a great example of how “wisdom” can lead a person to be miserable and unhappy.

    For another comparison, ask yourself: who were happier? The great philosophers of the past or the great mystics of the past that were ignorant to philosophy? My answer would be that the mystics were happier.
  • Abortion


    1. If you destroy the fetus then you destroy the baby (that's what abortion is - potential)TheMadFool

    No, you destroy the potential baby (the fetus) (I'm thinking about a 1 year old as an example of a baby, but perhaps you can tell me which age you are thinking of). A potential baby is not a baby, and you can't destroy what doesn't exist.

    The potential baby is not a baby in actu, just like a seed is not a tree in actu despite being a potential tree.

    But what's your point here? Are you saying people who cleanse their garden of scattered seeds or crush them should be charged with deforestation? (That would be one of the absurd consequences, if arguments from “potentiality” with that logical structure were valid).

    2. If you can't destroy the baby then you can't destroy the fetus (1 contra)TheMadFool

    That's only if 1 is true, which it isn't.

    7. If you destroy the seed then you destroy the tree (potential)TheMadFool

    False, for the same reason 1 is false.

    8. If you can't destroy the tree then you can't destroy the seed (7 contra)TheMadFool

    False, for the same reason 2 is false.

    11. If a seed is not a tree then you can destroy the seed (your claim)TheMadFool

    That's not my claim, my claim is that if an argument with a logical structure such as:

    «If I can prove that the fetus must be labeled as a person because it has “personhood”, then killing a fetus has to be punished just like we would punish murdering any other thing labeled as a person».

    ... were valid, then this other argument, which has exactly the same logical structure, would also be valid:

    «If I can prove that the seeds must be labeled as a tree because they have “treehood”, then destroying a seed has to be punished just like we would punish burning the same amount of trees, therefore the person who cleansed their garden of scattered seeds should receive exactly the same punishment as those who burn just as many trees as the seeds he destroyed».

    Since nobody seriously considers that the second conclusion is true («therefore the person who cleansed his garden of scattered seeds should receive exactly the same punishment as those who burn just as many trees as the seeds he destroyed»), then we conclude that arguments with such a logical structure are not valid, including the one about the potential baby.
  • Abortion
    Yes but the value of a seed lies in its potential (tree), not in itself.TheMadFool

    But I think 180's point with that analogy is that an actual tree is not the same as a potential tree, and so for instance we would not say that cleansing a garden of scattered seeds should be punished just as harshly as burning an equal amount of fully grown trees, because both are “deforesting”.
  • A question concerning formal modal logic


    Ok then, do you accept that the Law of Contradiction is necessarily true? For there sake of this discussion, I'll maintain that it is.

    If so, you must admit that the proposition:

    "It is both a wave and a particle";Banno

    ... can't be true if you can replace “not a wave” with “a particle” without changing the meaning of the sentence.

    If that proposition is true, then particle cannot mean “not a wave”, where both of those words “wave” in that sentence mean exactly the same thing. If they don't, then that proposition does not assert that A and ¬A, since the word wave (in the sentence resulting after you replace the meaning of “a particle”) would not mean “something that is not a particle”. It would have changed meaning in that case, and thus no longer have the same sense.

    That's why the Law asserts that you can't assert A and ¬A, unless the second A has a different meaning/sense.
  • A question concerning formal modal logic
    That's a different question. A possible world comes about as the result of a "what if..."; then we can see if that "what if..." leads to a consistent story or not. If it is inconsistent, then there can be no such possible world.

    That is, logic gives us a grammar with which to judge our statements.
    Banno

    Ok, so we more or less agree then.

    But my point was that a statement such as “It is not the case that the sun both was and was not a star, at the same time and in the same sense ” doesn't seem to be merely a truth about “grammar”, but also about the world, and it would seem like that proposition was true before any human being verbally constructed it or thought of it.

    I am aware this leads to other difficult questions, related to philosophies like psychologism and the disputes between the advocates of that philosophy and people like Frege and Husserl, so I won't talk about it anymore here to avoid derailing the thread.
  • A question concerning formal modal logic
    Possible worlds are constructed by fiat, not discovered.Banno

    Is logic constructed by fiat? Possible worlds depend upon what is logically possible/ impossible (that's how they are defined), and it seems we don't construct “by fiat” what is and is not logically possible.
  • A question concerning formal modal logic
    So do the proofs you mention indeed first prove there exists a unique individual with such and such properties that is then named 'God'?TonesInDeepFreeze

    I don't think so, they define God as having certain properties (perfections or “great making properties”) first, and then through analysis of the concept of “God”, defined as the subject of all perfections or greatest conceivable being, they argue that the proposition “God exists” is analytically true, that is: that God's non existence is as impossible as there being an object that was both round and triangular at the same time and in the same sense.

    Especially, one can't just assert without proof that there does exist a unique individual having certain properties and then go on to demonstrate that that individual then has other properties for a QED.TonesInDeepFreeze

    That's true, here:

    But it would mean something like: Necessarily, there exists/is an x (God), such that a (the greatest conceivable being/ subject of all perfections) = x.Amalac

    ...I should have just said that “there is [not “exists”] an x (God), such that...” (though as I said later in the ontological argument it is argued that God's existence is analytic), since otherwise one would just assume the existence of that “x” right away, which is not what I meant to write.

    That way, the existence of x is not assumed, but (supposed to be) proved from analysis of the meanings of the terms involved.

    How does a system of modal logic talk about its own semantics? I'm not saying it can't be done, but I'd like to know how it works.TonesInDeepFreeze

    The corollary of axiom M states that A→◇A , so systems that have axiom M do consider the actual world as one of the possible worlds, since a possible world is simply a world, real or imagined, that does involve any contradictions, and so the actual world is one of them.
  • A question concerning formal modal logic


    That strikes me as being an additional premise. Of course we can't rule out that additional premises have consequences.TonesInDeepFreeze

    Actually, I think they claim that follows from the definition of God, using corollary B or corollary 5. So it's not a premise, but rather something that follows from other premises (they say).

    You are right however, in that even if one accepted S5, the modal ontological argument would still have major problems, like dealing with the objection that existence is not a predicate or is a second order predicate, since that premise (that existence is a predicate) is required (it seems to me at least) to hold the claim that the greatest conceivable being or subject of all perfections exists in all possible worlds.

    The argument would go something like this:

    The actual world is one among the possible worlds (this again follows in some systems of modal logic). If one admits that god exists in all possible worlds, that would imply that god exists in the actual world.

    And so, if one accepts that it is possible that it is necessary that god exists in all possible worlds (meaning: in some possible worlds, necessarily God exists in all possible worlds), then it follows that in all possible worlds, god exists in all possible worlds, and therefore “god exists in all possible worlds” is true in the actual world, which is one of the possible worlds in which that statement is true, and therefore god exists in the actual world.

    All this follows if one accepts system B of modal logic, from the corollary of axiom B (if the modal ontological argument is valid):

    ◇□X → X (If it is possible that it is necessary that X, then X is the case).

    Likewise in system S5, the corollary of axiom 5:

    ◇□X → □X
    Amalac
  • A question concerning formal modal logic
    Now, suppose an individual is a member of a certain universe, of course that individual is not a member of certain other universes. So, yes, there is no individual that is a member of every universe.TonesInDeepFreeze

    Hmm, but isn't that what the advocates of the modal ontological argument would reject? They would not be convinced with just “of course that individual is not a member of certain other universes” because they argue that God, and God alone, is a member of all “universes” or “possible worlds” without exception.

    Or is there some significant difference between “universe” and “possible world” in the case of God?