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.

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.

The point, though, is that solipsism has a very long and well established meaning: — Clearbury

Then cite some passages from those who use it without relation to the isolation of the individual.

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

My challenge is simple. I will not withdraw it.
But I will leave the discussion, upon your request.
Fare forward, as Eliot said.

But how can something unextended 'expand'? — Clearbury

When one instance of the extended universe collapses into an unextended nothingness, the following compression of all remaining energy and forces causes an explosion (big bang), and the explosion creates a new instance of extension. When it cools down, atoms begin to form, followed by the compounds of matter and things.

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 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. — Clearbury

Your idea of mind seem to be coming from some sort of dualism. That's fine. But my idea of mind is based on the mind as a function of body. That means mind without body is impossible. As soon as body dies, mind dies also by necessity.

In this situation, the question naturally arises, and need to be explained i.e. how mind can exist and operate without body. This is a quite complicated process I would imagine.

If the mind without body arguments keeps going on without clearing the inevitable question first, then it would sound like a paranormal rants. We want to avoid that.

But only something that occupies some space can expand, as there needs to be the space it occupies and then expands into. — Clearbury

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

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. — Clearbury

The problem is that you don't explain anything, you only say that you do, while dismissing and ignoring the objections. That's disingenuous.

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.

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. — Clearbury

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. It has no linguistic apparatus either which is closely linked to logic and reasoning. All it could do is dreaming, but dreaming is only possible via brain. With no bodily organs available to the mind, we wonder how it could even dream, imagine or even have illusions and hallucination.

The OP title says it is "an evolutionary defense", hence some counter arguments is being presented against the OP's assumptions.

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).

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. — Clearbury

So whence comes a theory of evolution worth considering in light of this posit?

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.

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. — Clearbury

The biological theory of evolution is based on all sort of empirical evidence. Is empirical evidence for your theory of evolution even possible in principal?

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. — Clearbury

Your definition of solipsism equates to eastern philosophies such as Brahmanism and mind only Buddhism and Western philosophies such as Neoplatonism. In their various ways they posit that here is only one mind and that the supposed existence of many minds is an illusion. 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.

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.

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.