Isn't an alternative perspective permissible also, that belief is sufficient to bring all kinds of social constructions/facts/actions into existence? — Nils Loc

My claim was about moral principles. It is about those that it is beyond serious dispute do not come into being through simply believing in them.

We can describe conventions within a society, but those are not moral principles. Such descriptions will not be normative. ('People in Peru have a tradition of burping after meals' is not a normative statement. "You ought to burp after a meal in Peru because they have a tradition of doing so" is a normative statement.

And they certainly won't be moral principles, as whether the conventions are right or wrong remains an open question.

I am not cherry picking or anything of the sort. I am simply explaining why there's a problem here and why - other things being equal - an evolutionary account seems to threaten the reality of moral principles.

You claim that you posited a single mind for a single instance — Corvus

No, I posit one kind of thing - a mind - and one instance of it - so just one mind.

But is mind something which can be posited? — Corvus

Yes.

How did you do that, if that operation had been done? — Corvus

I don't understand what you mean.

If it were your mind, then how does your body function without the mind, which is posited to the OP or to some other location or storage? — Corvus

The mind I posit has a disposition to replicate its state with small changes. So it starts in a state and this starting state causes the mind to be in a subsequent state, a state which will be extremely similar to the previous one. And on and on it goes. Nothing is stored.

if your body doesn't exist, because it is disembodied from the mind, then how were you able to read my posts without the sights, and replied to them with no hands and fingers to type up? — Corvus

You don't seem to be getting the picture. There's just a mind having experiences. There's nothing else.

I do not follow you. I am positing one kind of thing - a mind - and one instance of it.

Now, it is clearly conceivable that minds can exist without any material entities existing. There is nothing incoherent in the idea.

But even if minds can't exist without a material entity existing, that doesn't affect my case, as I'm still only positing one kind of thing and one instance of it.

Whether minds can exist apart from material bodies or not is a red herring. The issue is whether, by just positing one mind in one kind of mental state and with one disposition, we can get the work done of explaining all else. That's the issue.

Not all explanations are external to the thing explained. Here are examples of things that are explained by an internal reason, that is, out of logical necessity or inherently.
• 2+2=4 because II and II are contained inherently in IIII.
• All triangles have 3 sides by definition, or inherently.
• Same for "All bachelors are unmarried".
• Likewise, if the property of existence is contained in the definition of a thing, then its existence is explained inherently. — A Christian Philosophy

All you're doing there is drawing attention to some claims whose truth is explained by appealing to truths of reason. It has nothing to do with existence being contained in the definition of a thing.

It is a truth of reason that all contradictions are false and thus correspond to nothing in reality. The notion of a married bachelor, given the conventional meanings of those terms, contains a contradiction. And thus by appeal to the law of non-contradiction we can 'explain' why there are no married bachelors.

But the principle of sufficient reason - which says that everything has an explanation - must now be applied to the law of non-contradiction. What explains why it is true?

No good appealing to the fact it's obviously true. For that is no explanation. And no good saying 'it is a necessary truth' for that explains nothing either.

If you think the basic laws of reason - and again, it is those that 'explain' why there are no 4 sided triangles or married bachelors - do not require explanation, then you're rejecting the PSR, for you'd now be saying that it is only things 'other than' the basic laws of reason that need explanation.

The Principle of Parsimony: the simplest explanation that accounts for all the data is the most reasonable one.
Sufficient in the PSR means that an explanation should be neither more than sufficient (i.e. it should be the simplest one), nor less than sufficient (i.e. it must account for all the data); but should be just sufficient. — A Christian Philosophy

No, they're absolutely not the same principle differently expressed. Sufficient and efficient do not mean the same thing.

Take an event - P.

What the principle of sufficient reason says is that there were causes sufficient to bring P about. Causes sufficient to bring about P can be much more than is necessary. Maybe P was brought about by 100 causes or maybe 20 or maybe 1. The principle of sufficient reason says precisely nothing about that. Why? Becasue they're all SUFFICIENT to explain it. Not necessary. But sufficient. All the principle of sufficient reason rules out is one scenario and one alone: that NOTHING brought about P. That's it.

Now, it is obviously unreaonable to supose that the event had 100 causes when one would have done to expain it. But the unreasonableness of that supposition is due to the principle of parsimony, not the pricniple of sufficient reason.

Note, Tony - who posits 1billion causes for P - and Mary - who posits just one - are both respecting the principle of sufficient reason, but Tony, unlike Mary, is violating the principle of parsimony.

You are coming to conclusions about how people are disposed to behave.

Ethical principles are normative. That is, they prescribe. We can describe them. But what we are describing when we describe an ethical principle, is a prescription, not a description of a disposition.

Something that merely describes human behaviour - or typical human behaviour - is not an ethical principle, for it has no prescriptive force.

For example, it may be that given an evolutionary story about our development we can conclude that most men will be disposed to cheat on their partners when they can get away with it.

That's not a moral principle. This: "You ought not cheat on your partner" is.

Exactly what ontological commitments moral principles come with is a matter of dispute. But there are some things that are agreed. The first is that "people generally cheat on their partners when they can get away with it" is not - not - a moral principle in any sense at all. And thus by simply demonstrating why it might be reasonable to believe humans have certain dispositions, you have not demonstrated that ethical principles exist.
The second agreed upon claim about ethical principles is that believing them does not make them so. That is, to 'believe' that we ought not cheat on our partners is not equivalent to it being true that we oght not cheat on our partners.

The so-called 'evolutionary debunking argument' against morality arises as a result of these truths. For given that it's not sufficient for us to believe an act is wrong to make it so, ethical principles - truly to exist - require something more than mere belief in them. And all an evolutionary account is going to do is explain why it was adaptive for our ancestors to have formed such beliefs. So, the evolutionary account seems able to explain - in a parsimonious way - why it is that humans believe there are moral principles. But it does this without positing any actual moral principles (remembering that 'believing' in a principle is absolutely not sufficient to make it exist). And thus on grounds of simplicity, we should conclude that though humans are disposed to believe in the reality of moral principles, in reality there are none.

That's not a conclusion I draw, but I don't yet see a way to block it.

Your question answers itself. It is simpler to suppose a mind to exist by itself than it is to suppose it exists in a body, for then you're not assuming a body too.

At this point I think you're not really interested in listening to what I have to say, as I have already told you numerous times - and in the opening post - what the term solipsism is being used to refer to. As I say, I really am not interested in discussing things with someone who is hellbent on mischaracterizing the view I am defending.

What is the purpose for doing this? What is the solipsism trying to prove? — Corvus

My purpose is to try and figure out what's going on. And 'solipsism' isn't trying to prove anything. It's a thesis. I am the prover. And I'm not really trying to 'prove' it, just show that it is a simpler thesis than its nearest rival. Whether that proves it - that is, puts its truth beyond all reasonable doubt - is another matter, as simplicity is only one epistemic virtue not all of them.

No, for solipsism - as I keep saying - is the thesis that only one mind exists. That's certainly how Russell was understanding the term (else his joke makes no sense) and how he was assuming everyone else understood the term and how I am using the term.

Note: the idea that there is only one mind and that there are also lots of mind is straightforwardly contradictory. It does not answer to the meaning of the word 'solipsism' and it is not coherent. It's also clearly not what I am talking about or what Russell is talking about.

I don't think I can discuss this with you any longer. If you want to insist upon understanding the term solipsism incorrectly, that is entirely up to you. But I am not interested in discussing matters further with someone who insists upon using terms incorrectly as you're just going to keep strawmaning the view I am trying to defend, which is tedious.

That's not what I understand the word 'grounding' to mean.

Propositions are about things. Causes seem to be what explain things. This is why a 'causal reason' and an 'explanatory reason' are (arguably) synonymous. And that is why the principle of sufficient reason could just as well be called the principle of sufficient explanation.

When it comes to grounding, the 'grounding' of something refers to its basis, or what in some sense produced it. So, that the act was wrong is 'grounded' in the fact it hurt someone (or something like that). But as I noted, the 'grounding' of something does not seem to be sufficient to explain it, even though it is going to be part of its explanation.

The fact I am thirsty is the ground of my decision to go and get myself a drink, but it cannot be the full explanation of why that decision occurred, for I too am in the mix (I caused myself to make a decision in light of my thirst, but the thirst alone does not explain my decision even though it grounds it).

I am not sure I quite see that an explanation is a proposition.
I'm not a fan of 'grounding' as it is not clear to me that it's a good alternative to explanation.

For example, let's say I decide to order a pizza because I'm hungry. I am the cause of my decision. But I could also say that my decision was grounded in my hunger, as that was why i made the decision.

The explanation of why that decision event occurred can't just make mention of my hunger. It has also to make mention of me causing it - causing the decision - in light of the hunger.

A belief in a moral principle is not sufficient for the principle to exist.

We're going in circles here.

If you believe it is right to rape people, that doesn't make the principle 'rape people' exist. It doesn't exist. There is no such principle. Some people may believe there is - but that doesn't make it exist anymore than believing there's a god makes a god exist.

Yet a belief is sufficient to explain behaviour. And from an evolutionary perspective, it was 'beliefs' in moral principles that conferred the reproductive advantage by promoting adaptive behaviour. That doesn't mean the principles themselves exist.

That's precisely why there's a problem here - one known as the 'evolutionary debunking argument' against morality.

Actual moral principles seem entirely dispensable when it comes to explaining why creatures who believed in such principles would enjoy a reproductive advantage over those who did not. And thus the simplest and best explanation of why it is that people today believe in moral principles is not that there actually are some, but that the mere belief in them was adaptive for their ancestors.

I don't believe the evolutionary debuking argument against morality is sound, but we should at least make it clear that it presents a real challenge.

Ha, all he seems to have done is make something that is quite easy to understand an order of magnitude harder by use of those terms.

'Fact' is not the right term, as we're talking about existences. Facts are 'about' things, but they are not really things in their own right - so I don't know why he's using that term rather than the much clearer 'existence' or 'object'.
 
Autonomous isn't a good word to use for 'has no explanation'. It implies that the thing - the object - somehow explains itself or something (which it doesn't - it just exists and has no explanation whatsoever).

And 'substantive' isn't a good word for 'has an explanation for its existence', as that's simply not what it means.

And to use 'grounding' for explanation or cause hardly makes things clearer.

He might as well have decided to call 'things that exist and have no explanation for their existence' 'Cheesy turnips' and things that exist and have an explanation for their existence 'Saucy bananas' and used 'bilge water' to mean 'exists' and 'grunty' to mean 'explanation'. Then "For every saucy banana bilge water there are some bilge waters, the Xs, such that (i) the Xs grunty Y and ii) each of the Xs is a cheesy turnip".

Just goes to show, some people are not interested in making things clear. It's quite a common strategy in academic articles - I think the idea is simply to wear down the reviewers so that they just give up and give it a pass.

I agree. It seems to me that, based on the reasoning above, there has to be a bedrock of facts which have no further explanation. — flannel jesus

Yes, it implies that there are some things that do not have explanations. The most common modification in light of the above is to hold that it is only those things that have 'come into being' that have explanations rather than everything. Those things that have not come into being just exist and that's as much as one can say about them.

But this does not get one anywhere near theism, as there's just no reason to think that a thing that exists and has not come into being will be a person, and be omnipotent, omniscient and omnibenevolent.

And given what in fact exists, it seems reasonable to suppose that if it was created by a person (or more reasonably, persons), the person was not God.

You seem to be committing some kind of weird category errors — Janus

And you seem not to be grasping the point. You said, and I quote

Of course there are such principles otherwise people would not be able to follow them — Janus

That's obviously false. 'Believing' there are such principles enough to explain why a person does as they do. One does not have to suppose that the principles themselves exist. Again, lots of people think they're following God - that doesn't show God to exist.

What do you mean by "actually are such principles". Of course there are such principles otherwise people would not be able to follow them. It doesn't follow that all those actual moral principles are correct. — Janus

That's like arguing that God must exist otherwise people wouldn't be able to do what they believe God wants them to do!

If someone believes God wants them to reproduce, then they may well reproduce in light of that belief. That doesn't show that God exists.

LIkewise, if someone believes that it is morally right to reproduce (or to behave in ways that will make reproduction more likely), then this may well cause them to reproduce. That isn't evidence that it is morally right to reproduce - it's not evidence there really is a moral principle enjoining such behaviour.

On that view Ladd-Franklin is not being illogical at all. It is only in relation to the standard solipsism which says that only my mind exists and that all you others are mere projections of my mind that she is being illogical. — Janus

She is being illogical as solipsism is the view that only one mind exists. So a person who thinks it is surprising that there are not other persons who are solipsists is being illogical, as by hypothesis there can only ever be one solipsist if solipsism is true.

It's based on simplicity. Both theories are explaining the same data - the empirical data. But the standard evolutionary theory posits lots and lots of replicating and randomly mutating entities, wheres my theory posits one mind replicating and randomly mutating its mental state.

The evolution of the Earth, over 4.6 billion years, has given rise to the laws and principles that regulate both the natural environment and our existence. Within these evolutionary trends, we can find the essence of the ethical principles and moral norms that humanity seeks to identify. — Seeker25

This is a claim you made in your initial post. But the point is that you seem to be confusing the evolution of moral beliefs with the evolution of moral principles themselves. This is a well-known fallacy. That we may have evolved to 'believe' that there are moral principles - moral principles telling us to behave in what turns out to be reproductively advantageous ways - does not show us that there actually are such principles. On the contrary, it implies there are not. It was the mere belief that conferred the advantage - something it would have done regardless of the actual existence of any such moral principles - and so simplicity bids us conclude that the principles themselves do not exist.

Admittedly, my theory has changed slightly as it is now simpler than the original.

But the original evolutionary story involves random mental state generation and a mind disposed to remember sequences of mental states that seem closely to resemble one another. It experiences A. Then later it experiences - by random (and with enough time this would happen, of course) - B, a state that seems very similar to A. This it remembers and is now disposed, should it ever experience A again, to experience B following it, as it has a disposition to recall what it has remembered.

Eventually B will be experienced being followed by C, a state that closely resembles it. And now the sequence A, B C is remembered and should the mind ever experience A again - which it will given enough time, it will experience A, B, C. And so on.

In this way a potentially infinite sequence of closely resembling states can evolve. And the idea is that this is what 'this' is.

But now I have simplified it further. The standard theory of evolution has physical things replicating themselves with random mutations. Ok, so i will simply posit a mind that is disposed to replicate its initial mental state but with random changes. And that is what this is. That's simpler still. Both theories are simpler than the standard evolutionary alternatives, but the latest is the simplest of all and it seems to get the job done by positing one mind, one initial state of that mind, and one disposition.

I have always been entirely unimpressed by this kind of cosmological argument for God. For even if its premises are true - and they seem highly questionable - it does not imply God at all. Where atheism and theism are concerned, it does not tell more in favour of one than the other.

The principle of sufficient reason states that everything - everything, not just some things and not others - has an explanation for its existence.

That principle is by no means obviously true. For after all, if it true, then it generates an infinite regress. A cannot be explained by A, and so B has to be posited. But B cannot be explained by B, and so C has to be posited. And on and on for an actual infinity.

So, it seems false upon reflection. And if one thinks it is not false, for one thinks there is nothing problematic about there being actual infinities, then it does not lead to God, but to an actual infinity of prior explanations. God isn't in the picture at all.

If one modifies the principle so that it is only contingent existences that require explanation, then all you get to conclude is that there exists at least one necessary existent. But there's no reason to suppose that necessary existent is God. That's like concluding that becuase 'someone' clearly shot Kennedy, then it must have been Mrs Smith at 28 Acacia Avenue.

In fact, it is worse than this. For it seems self-evident that we - minds - are not necessary existences, but contingent ones. I am a contingent existence. So why assume that a necessary existent would be a mind? Minds seem no more or less contingent than physical stuff, and so to suppose God - a person, a mind - is the necessary existent is not just a huge leap, but an implausible one.

And it gets worse still. For consider this. Necessary existences confer necessity on what they cause. And thus a necessary existent can only explain other necessary existences (and it woldn't really be an explanation either, as by hyothesis if something is necessary, it does not need explaining). To see this note that a necessary existent either contingently causes something else to exist - but if it does that, then it was contingent whether it would cause it or not, and thus no explanation is provided. In order not to generate a need for explanation, the necessary existence must be supposed necessarily to cause what it causes. But if it necessarily causes what it causes, then what it causes to exist, exists of necessity as well. Yet necessary existences are supposed to explain contingent existences! They can't - as nothing a necessary existence explains will be contingent, but will be necessary too.

Necessary existences are actually quite useless explanatorily, for all they do is confer necessity on what they cause, but as what needs explaining are 'contingent' existences, they are useless.

But again, even if they weren't useless explanatorily, there is just no reason to suppose any necessary existent is God and positive reason to think it wouldn't be, given that all the other persons of our acquaintance are clearly contingent existences not necessary ones.

They are still the same. In the principle of parsimony, it is reasonable to pick the simplest of 2 explanations that account for all the data because the less simple explanation is superfluous, that is, more than sufficient. Both principles demand that the explanation or reason be just sufficient, not more, not less. — A Christian Philosophy

No, the principle of sufficient reason says that everything that exists has a sufficient explanation of its existence. It says nothing about simplicity. Note, the more complicated of two explanations is still sufficient to explain. (I think you're conflating sufficiency with efficiency)

The principle of parsimony is clearly a distinct principle of Reason from the principle of sufficient reason. Note, one could quite consistently reject one and not the other.

I agree that a thing cannot be its own cause, yet a thing can explain itself. — A Christian Philosophy

How?

You have two options and neither constitute self-explanatory objects.

The first is to insist that some things exist 'of necessity' and hope that this will somehow pass as an 'explanation' of why the thing exists.

Problem: that's no explanation at all. On the contrary, a necessary existence - if there are such things - is something that has no explanation. It's not self-explanatory. It's incapable of explanation. Those who believe in necessary existences are denying the principle of sufficient reason, not endorsing it. The principle of sufficient reason says that EVERYTHING that exists has a sufficient expalnation of its existence, not just some things and not others. So that's not going to work at all.

The other option is to suppose that there are some things that exist and have not come into being. that is, there are some eternal existences. The problem is the same though: that's not an explanation at all.

Another problem with disembodied mind is that, it is devoid of all the sensory perceptions, which is the source of thoughts, feelings and sensations on the external world. — Corvus

What's being posited is a mind that is in a mental state - so, whatever total mental mental state you are in now (including all experiential states), just assume the mind is in it.

There is no need to assume that the mind has a physical substratum. To think you do have to make that assumption is already to have assumed physicalism. And whether physicalism is true is the issue.

So, just assume a mind in a mental state. Now assume the mind has one disposition: to put itself in a mental state that closely resembles the one it is already in. So, its disposition is just to replicate the state it is in but it makes small changes every time it does this. That gets the job done. That's what this is (or could be).

Principles of reason don't exist other than as thoughts or sentences. — Janus

So if I just 'think' the theory of evolution is true, then that's sufficient for there to be reason to believe it is true?

That's not a defensible theory about what principles of reason are. There's a huge debate over exactly what reality would need to be like in order to contain any, but the view that 'if you think it, it is so' and the view that principles of reason are shaped sized things are not in serious contention. Hence the problem.

Laws of nature are not laws of reason, so it is not clear why you are mentioning them. A law of nature is just a description of a regularity in the natural world. That's not at all what a principle of reason is and so is irrelevant.

There is no evolutionary debunking challenge to laws of nature, for an evolutionary account presupposes that there is a natural world - and a law of nature just describes its behaviour.

A mere assertion—the argument for it is missing. — Janus

Completely false. I did not 'assert' it. I patiently explained the nature of evolutionary debunking 'arguments' to you. Twice. If you don't think I argued a case, then I see no point in continuing this exchange.

Evolution is a theory and as such is not a part of the physical landscape, so it belongs with reason. — Janus

That misses the point. The best explanation of why we believe there are reasons to do and believe things is not that there actually are, but that believing in them conferred an evolutionary advantage.

The belief in principles of reason is what confers the advantage, not the actual existence of any.

This is a problem because if there is a reason to believe that the theory of evolution is true, then principles of reason exist.

Thus, if there is a case for an evolutionary account of our development, then it can't be the full story, because if it was the full story then there wouldn't be any cases possible for anything.

Unlike a balloon, the universe has no outside into which it can expand. It creates the space. — jkop

I can make no sense of that. You haven't explained how something non-physical can expand. Something cannot expand if there is no space for it to expand into. And space cannot expand unless there is space for it to expand into.

As I say, you are either using the word 'expand' in some metaphorical sense, or you mean it literally, but it you mean it literally then you are just talking about material entities and the space they occupy.

The issue here is simplicity. The thesis I have put forward is simple. To challenge that claim of mine, one would need to argue that there is an 'as' simple thesis that does just as good a job at explaining everything.

I don't think there is. Note what you have to do. You have to posit one thing. Just one. And you have to attribute to it one simple disposition. Just one. And you have to attribute to it one state. From those elements, you need to derive everything else. The solipsist evolutionary theory I have proposed does that. It explains how experiences of the kind I am currently having could have arisen given just those three elements: one thing, one state of that thing, and one disposition.

The issue does not seem to be what kind of a thing the mind is. It does not matter for simplicity's sake whether minds are material or immaterial. What make the thesis simple is that only one kind of a thing is posited - whatever kind of a thing a mind is - and only one instance of that kind of thing is posited.

I do not see why the principle of sufficient reason is equivalent to the principle of parsimony. They seem like two quite different principles. The first says that for anything that exists, there is an explanation of its existence (the word 'reason' in 'principle of sufficient reason' refers to an explanatory reason). The principle of parsimony says that for any two or more possible explanations, we have reason to think the simpler one is true, other things being equal. The word 'reason' in the principle of parsimony refers to a justifying reason. These are not the same principle at all, I think.

I also do not see why accepting the truth of the principle of sufficient reason is required to be able to engage in intellectual inquiry. For example, imagine I think it is false for I think that if it is true, then some things must explain themselves (for not everything can have a cause external to it - as that generates a regress - and nothing can be the cause of itself, as that's a contradiction). As nothing can explain itself, I conclude that some things exist and have no cause of their existence (and thus that the principle of sufficient reason is false).

Why does denying the principle of reason - as I have just done - preclude me from using my reason to find out what is true? I think our reason is our source - our only source - of insight into the nature of reality. And it was by using it - perhaps incompetently, admittedly - that I arrived at the conclusion that the principle of sufficient reason is not a true principle of reason at all, but contrary to reason. I do not see, then, why rejection of the principle of sufficient reason undermines the project of using reason to find truth. For all I have concluded - and concluded by using my reason - is that some existences do not have explanations. I have not concluded that nothing has an explanation. And i have not rejected the principle of parsimony either, for i plan on using it to try and find out which existences are the ones that lack explanations.

But only something that occupies some space can expand, as there needs to be the space it occupies and then expands into. So something that is not extended in space is not capable of 'expanding' except in some metaphorical sense.

I think this is all beside the main point though. The solipsist evolutionary theory posits one kind of a thing (a mind) and one disposition (the disposition to create a similar mental state to the one it is originally in) and gets everything out of that. I still do not see how an alternative that starts with something else is going to be able to explain as much with as little.

I asked you kindly not to do what you are now doing.

Principles of reason seem as jeopardized by an evolutionary account as moral principles are (which are, i take it, just another form of principles of reason anyway), because principles of reason are not part of the physical landscape in which evolutionary forces are operating. Even if they accurately describe that landscape, the fact remains that they are not part of it, and as such all that needs to be posited is the belief in such principles, not the principles themselves.

So to explain why we have the beliefs we do about the sizes and shapes of things in our immediate environment we posit actual sized shaped things in our immediate environment. Being disposed to form approximately accurate beliefs about them would get selected for. So in that case positing the actual existence of what the beliefs are about helps explain why we have them.

But in the case of principles of reason, we do not have to posit the principles themselves, but only the beliefs in them. It is believing in the truth of the law of non-contradiction that helped my father breed more successfully, because by believing in it he would have avoided (for longer) being killed by something shaped and sized. But as it is the shaped and sized thing that would have killed him, not a principle of reason, then we do not have to posit any principles to explain why my father survived and bred.

I don't yet see a way around this. Nothing stops one from supposing that there really are principles of reason, but their actual existence would be pure coincidence given a wholly evolutionary account of our development.

that it is psychologically impossible to believe, — Richard B

That seems false and also not to provide us with a reason to think it solipsism false.

It is not psychologically impossible to believe that you are the only mind in existence. It may not be a very reasonable view - though that's what is at issue - but there is nothing impossible about it. If you are in any doubt about this, just imagine what you'd believe if you woke up as the sole survivor of a nuclear holocaust. You'd believe you're the only mind in existence. That's to believe solipsism is true. It's entirely psychologically possible to believe it, then.

But more importantly, being psychologically incapable of beileving something is not evidence that the proposition in question is false. I find myself psychologically incapable of believing I will die. But that is not evidence I am immortal.

I once received a letter from an eminent logician, Mrs. Christine Ladd-Franklin, saying that she was a solipsist, and was surprised that there were no others. Coming from a logician and a solipsist, her surprise surprised me — Richard B

All that quote from Russell does is reveal how illogical Mrs Christine Ladd-Franklin is. That is, it reveals that she's not very good at understanding the implications of a thesis - which is surprising in a logician. Russell is making fun of Ladd-Franklin, not making fun of solipsism.

Mind without physical body assumption is not simpler than mind with body, because you must explain on how the mind ended up with no body. How can mind operate without body is far more complicated than starting with mind with body which is empirically and logically natural and sound. — Corvus

I think you have missed the point. Posits are not expalined, that's what makes them posits. Positing two things is more complicated than positing one, other things being equal. thus, I posit one thing - a mind - and I see how far I can go with it.

Whether the mind is a material or immaterial thing is actually beside the point. If you posit a material mind then you have not explained it, but posited it. If you posit an immaterial mind then you have not explained it but posited it. If you posit non-mental material things then you have posited them and not explained them. And so on.

It's what the term means. And that's how I am using it. Solipsism is the view that one mind - and one mind alone - exists.

it's not even a view about what minds are made of, as it is entirely compatible with physicalism about minds.

Monism is the view that one kind of stuff exists. The two are not equivalent, for there is no inconsistency in holding that only one mind exists but that the mind in question is made of two kinds of stuff.

Simplicity speaks against that and so it is implicit in my case that the mind that is being posited is a simple thing and not a complex thing.

The point, though, is that solipsism has a very long and well established meaning: it is the view that only one mind exists. But please do not drive this discussion into a discussion of the use and abuse of the term solipsism. That is a linguistic matter and not a philosophical one and it is the philosophical case for thinking that there is one mind and one mind alone that I am interested in testing the credibility of.

The OP is based on the assumption, it claims, but assumptions are only accepted as reasonable and intelligible when it makes sense or is supported by evidence. — Corvus

I don't think that can be true as that generates an infinite regress. So unless we say that every assumption is as reasonable as any and all others, then some assumptions have to be acknowledged to be self-evidently true. That is, our reason represents them directly to be true, rather than us having to infer their truth from other representations of reason.

For example, the claim that, other things being equal, we have reason to believe a simpler thesis is true, is itself a self-evident truth of reason (or 'apparent' one, as we shouldn't rule out the possiblity it may be false). So, the assumption that the simpler thesis is true is more reasonable than the assumption that the more complicated theory is default true.

But these issues take us too far afield, I think. All I am doing is testing whether the solipsist evolutionary theory really is the simpler one. What status the epistemic virtue of simplicity has, how it vies with other virtues, is another matter.

But how can something unextended 'expand'?

On reflection, it doesn't even matter if we suppose only extended things to exist, for the solipsist thesis is still the simpler one. If the single mind I am positing is an extended thing (I see no reason to suppose it is, so this is just for the sake of argument), then nevertheless, by supposing that it has the disposition i described - the disposition for it to put itself in a mental state that closely resembles the one it starts out being in - then all the work can be done.

You are proposing various possible conditions for our experience. Solipsism imagines there is no way to verify other beings because they have to be produced by my activity. — Paine

That's a strawman. Solipsism is the view that only one mind exists. What I am arguing is that we can explain what needs to be explained more efficiently using that minimal posit than we can by supposing there to be something non-mental, such lots of extended objects (perhaps the mind is an extended object - but the same applies)

I'm having trouble parsing this one — Wayfarer

That knowledge cannot exist absent minds isn't in dispute. It doesn't raise a problem for the 'truth requires a mind' thesis.

It is the thesis that truth requires mind that seems to face a problem, for that theory entails that if no minds exist, there are no truths (yet it seems metaphysically for there to be no minds yet for there to be truths, for something can exist and not be a mind, and under such circumstances it would be true that it exists.

That's a different point. My point is that my thesis is simpler than the alternative. That is what jkop is disputing.

Other things being equal, we have reason to suppose the simpler of two theses to be true. There is no claim there that this is a guarantee of truth. And we can wonder why the simpler would be more likely to be true. But that we have more reason to think the simpler of two theses is true is not what's in dispute here.