v2: Contrast Panpsism Theory.

v3: Solipsism is a metaphysical, not a physical theory.   There is also an easy way to get out of solipsism by defining reality to be the minimal theory (in the mathematical sense) whose consequences include the entirety of mental existence.   This definition satisfies two important requirements:

1. the term 'reality' must be defined in some manner, and
2. properties of reality must not be assumed a priori.

v3: Solipsism Theory is useful mainly in demolishing positions that depend on vague or ill thought out conceptions of 'reality'.   This is especially so for conceptions where many onerous a priori assumptions are being made.   For example, the concept that reality is "something out there, independent of the human will".   This is fine as the conclusion of a derivation but it is intolerable as an assumption.   What exactly gives a person the power to assume something outside of oneself?   In particular, if the reason reality is independent of one's will is because one declares it to be so by fiat then in what meaningful way is reality independent of one's will?   This assumption entails a paradox analogous to an omnipotent deity creating a rock he cannot lift.

v3: If there is any problem in eliminating solipsism from consideration, it is only because of the poverty of metaphysical thought.

v0: Solipsism Theory

v2: The theory or view that the self is the only reality, and everything and everyone else is a wind-up toy.   Contrast Panpsism Theory.

v4: This is a reasonable attempt to define solipsism, but since solipsism is a false philosophy, the content of what it has to say cannot be consistently maintained in discourse.   Thus, in your definition, there is a contradiction in that even wind-up toys have reality, and since the phrase 'wind-up toy' is clearly meant to emphasize a difference from being a self, they clearly do not have the same reality as the self. -- Gerald Somerville

v3: Solipsism is a metaphysical, not a physical theory.   There is also an easy way to get out of solipsism by defining reality to be the minimal theory (in the mathematical sense) whose consequences include the entirety of mental existence.   This definition satisfies two important requirements:

1. the term 'reality' must be defined in some manner, and
2. properties of reality must not be assumed a priori.

v4: We are not free to define the word 'reality' in an arbitrary manner, and in talking in this way you betray the undue influence of solipsism on your own thinking.   (This is not to deny that the meaning of the word 'reality' can be developed or transformed by one's particular usage of it.)   Solipsism cannot be consistently maintained because communication presupposes a language shared by a community of selves.

v4: Furthermore, some properties of reality are necessarily assumed a priori – they necessarily follow from what the word means (however that meaning may be transformed).   This is in a sense what metaphysics is all about. -- Gerald Somerville

v3: Solipsism Theory is useful mainly in demolishing positions that depend on vague or ill thought out conceptions of 'reality'.   This is especially so for conceptions where many onerous a priori assumptions are being made. For example, the concept that reality is "something out there, independent of the human will".   This is fine as the conclusion of a derivation but it is intolerable as an assumption.   What exactly gives a person the power to assume something outside of oneself?   In particular, if the reason reality is independent of one's will is because one declares it to be so by fiat then in what meaningful way is reality independent of one's will?   This assumption entails a paradox analogous to an omnipotent deity creating a rock he cannot lift.

v4: Since no "Solipsism Theory" can be expounded – attempts to expound it will always end in contradiction, I would want to assert that there is no such theory, though still recognizing the existence of some trend or tendency called solipsism, and maybe the existence of people attracted to it called solipsists.   There is no getting out of the solipsism regarded as a terminal state – one must grab hold of whatever you can before you have fallen into the absyss. -- Gerald Somerville

v4: I think it is more useful to think about Descartes' methodical doubt, which gives us a more carefully articulated context to work with.   Despite using the phrase "conceptions of 'reality'", with 'reality' in inverted commas, I suspect you are influenced (as I am sure solipsists are) by Descartes' emphasis on questioning what is real as opposed to questioning what it is for something to be real, an emphasis which led to a false dichotomy between epistemology and metaphysics.

v4: You write (v3), 'What exactly GIVES a person the power to assume something outside of oneself?'   The very notion of being given something assumes that there is something outside oneself which is the giver.   But rather than focus on the person receiving something, I think it is better to focus on the utterances being made.   Indeed, the word 'utter' itself, so I am told, derives from 'out-er', hence originally close in meaning to our present word 'externalize'.   One's words are "coming out" of oneself, or indeed are one coming out of oneself.   (I am present to you in my words.)   The previous existence of an outside or an other might not necessarily be presupposed, but the subsequent existence of such certainly is supposed (implicitly) in an utterance.   Let us not worry about what was in your mind or mine prior to this discussion, or how this discussion got started, but rather focus on what we must necessarily suppose in this discussion as it proceeds.   For instance, a threefold distinction is supposed between writer (I) reader (you) and the discussion itself.   Writer and reader coincide when I read my own words, but the distinction between writer and reader still holds in the act of reading, which can be easily understood as a distinction between an earlier and a later self, although it is not really a simple temporal difference. -- Gerald Somerville

v4: The notion of willing itself presupposes the existence of something willed, something which results from the act of willing, which is not simply the act of willing itself.   The notion of independent existence can be a little confusing here, but all one needs for the argument is a distinction implicit in the notion of willing.   (Curiously, I think that a willing and what is willed might coincide, but the distinction between being an act of willing and being something willed nevertheless has to be made even for such an example of willing.   See above about reader and writer coinciding.) -- Gerald Somerville

v3: If there is any problem in eliminating solipsism from consideration, it is only because of the poverty of metaphysical thought.

v4: I agree, but we are both here considering solipsism, and thus we are both demonstrating the poverty of our metaphysical thinking.   Nevertheless, in recognizing our poverty, we are better off than the solipsists. -- Gerald Somerville

v4: We are not free to define the word 'reality' in an arbitrary manner, and in talking in this way you betray the undue influence of solipsism on your own thinking.   (This is not to deny that the meaning of the word 'reality' can be developed or transformed by one's particular usage of it.)   Solipsism cannot be consistently maintained because communication presupposes a language shared by a community of selves.

v10: In defining the word reality, I am betraying only my mathematical background.   It is common in mathematics to begin with a definition as if out of nowhere and then go on to justify the definition on the usefulness of the theorems it allows one to prove.

v10: Mathematics is based on formal reasoning and it maintains a distinction between definitions/theorems which are explicit and justifications for certain definitions, which are implicit.   In mathematics, everything is built from the ground up, or appears so, because only the bottom-up structure is made explicit.   Incidentally, the exact sciences work in the same manner as mathematics, by building from the bottom up.   Even worse so because scientists refuse to acknowledge the existence of thoughts and feelings as anything more than physical states.   If you mention qualia to them, even without using that term, you'll only get a blank-eyed stare.

v10: This contrasts sharply with the informal view you propose where you begin discussion of reality by referring to useless nonsense like "community of selves".   (Just what in the 9th circle of hell is that supposed to mean to a solipsist?)   This is because you draw no distinction between logical reasoning and justification.   Nor between formal and informal reasoning.   These fatal flaws are quite common in philosophy and are the reason the field is a failure.   Hopefully, Quine's influence (with his emphasis on formal reasoning, mathematics and a formal definition of existence) will change that fact.

v10: By "arbitrarily" formally defining reality (based on the implicit usefulness of the definition) one can begin from a solipsist state and end up a realist.   By using gibberish like "community of selves" and talking of the a priori properties of reality before a definition (meaning) of the term is even proposed, you're just whistling in the wind.

v10: The problem with solipsism isn't that it's contradictory (you will be unable to find any contradiction without recourse to sloppy informal reasoning) but that it's trivial.   Solipsism is no more interesting than matrix mathematics restricted to zero matrices.   But it is no less valid and logical for that.

v10: In fact, it is your informal top-down view which results in rampant contradiction.   By starting with arbitrary informal concepts and elevating them to the level of fact/reality, then going down to the fundamentals and building up reality on these fundamentals using formal reasoning … you end up with contradictory starting and ending positions.   This is a problem only because you accord them the same status.

v10: In concrete terms, most philosophers assume that space and time physically exist.   They elevate the sensory impressions of space and time to the level of physical reality.   Then they run into problems when physicists build concepts of spacetime that contradict the naive sensory impressions.   If philosophers merely kept their arrogance in check, by not assuming that space and time are within their purview, and let physicists do all the work then everything would be fine.

v10: The unmitigated gall and arrogance of philosophers is easily proved.   My conception of metaphysics is as the field which lays the basis for science and physics through pure reasoning.   OTOH, the typical philosopher's conception of metaphysics is as the field which short-circuits all of science and physics! Philosophers don't trust scientists who have had a lot more success than they have themselves.   The arrogance!   Incidentally, the philosopher's conception of metaphysics is nonsense since you can't short-circuit physics.   Even the existence of space and time (let alone their natures) aren't something you can prove by pure reasoning on naive sense impressions.

v10: By the way, the only influence Descartes had on me was to develop a deep distaste for philosophy.   His reasoning is risible, was risible back when I was in high school.   It took a lot of discussion on philosophy to transmute my distaste from philosophy to philosophers. -- Richard Kulisz

v4: We are not free to define the word 'reality' in an arbitrary manner, and in talking in this way you betray the undue influence of solipsism on your own thinking.   (This is not to deny that the meaning of the word 'reality' can be developed or transformed by one's particular usage of it.)   Solipsism cannot be consistently maintained because communication presupposes a language shared by a community of selves.
v10: In defining the word reality, I am betraying only my mathematical background.   It is common in mathematics to begin with a definition as if out of nowhere and then go on to justify the definition on the usefulness of the theorems it allows one to prove.
v11: I also have a mathematical background and my formal qualifications in Mathematics are greater than in Philosophy, so I don't think you can put the blame for our difference here on your mathematical background.   Indeed you seem naive about how Mathematics is actually done and the role that formalization has in Mathematics, but fortunately you include the phrase 'as if', which seems to be a grudging acceptance that even mathematical concepts are not defined in a purely arbitrary manner.   Conventions may not play as large a part in Mathematics as in ordinary English, but they are still necessary.

v10: Mathematics is based on formal reasoning and it maintains a distinction between definitions/theorems which are explicit and justifications for certain definitions, which are implicit.   In mathematics, everything is built from the ground up, or appears so, because only the bottom-up structure is made explicit.   Incidentally, the exact sciences work in the same manner as mathematics, by building from the bottom up.   Even worse so because scientists refuse to acknowledge the existence of thoughts and feelings as anything more than physical states.   If you mention qualia to them, even without using that term, you'll only get a blank-eyed stare.
v11: The key phrase here is 'or appears so', like the 'as if' previously.   Tbe point here is to distinguish between the order in which a mathematical proof is laid out and the order, in time, that some one constructs the proof.   There are a number of metaphors that have been used in Philosophy to illustrate this sort of distinction, e.g. the difference between the order in which an architect designs a building, and the order in which the builder constructs it.

v10: This contrasts sharply with the informal view you propose where you begin discussion of reality by referring to useless nonsense like "community of selves".   (Just what in the 9th cicle of hell is that supposed to mean to a solipsist?)   This is because you draw no distinction between logical reasoning and justification.   Nor between formal and informal reasoning.   These fatal flaws are quite common in philosophy and are the reason the field is a failure.   Hopefully, Quine's influence (with his emphasis on formal reasoning, mathematics and a formal definition of existence) will change that fact.
v11: Your supposed concern about what a particular phrase could mean to a solipsist illustrates how you concede too much the solipsist.   (See my first reply to your next paragraph.)   But, as you elsewhere make abundantly clear, you are not just claiming it is gibberish to a solipsist, but that it is gibberish absolutely.   I am not happy with the particular phrase 'community of selves', but even if I had used a more apt phrase I cannot be expected to know all for all your peculiar prejudices in advance, and the ease with which you dismiss my words as gibberish, instead of giving me the benefit of the doubt and making some effort to understand what I was trying to say, suggests to me that this discussion is not going to be very fruitful in comparison with the effort I have been putting into it.
v11: I do indeed distinguish between many kinds of reasoning and justification.   I see value in trying to formalize arguments, but I might have problems with the notion of formal reasoning, if that is taken as supposing that an argument could be completely captured in some system of formalization, effectively reducing it to a tautology, and the mechanical manipulation of symbols.   But even here, this does not mean I do not distinguish between form (symbol) and content (meaning) – only that they are not separable.   It is you who is failing to distinguish between a distinction and a separation.   The effort of trying to separate form and content may be valuable in analyzing an argument (and we could not even make the effort if we could not distinguish between them), but this does not mean that they can in fact be separated.
v11: Similarly, in Philosophy, explanation (concerned with meaning) and argument (concerned with truth) can be distinguished, but they are inseparable.   Acknowledging their inseparability in the one discourse does not have to result in confusing them.

v10: By "arbitrarily" formally defining reality (based on the implicit usefulness of the definition) one can begin from a solipsist state and end up a realist.   By using gibberish like "community of selves" and talking of the a priori properties of reality before a definition (meaning) of the term is even proposed, you're just whistling in the wind.
v11: But my main point is precisely that one cannot begin from a solipsist state   it is a mirage.   Every actual solipsist can only be someone tending to solipsism.   I am not trying to argue with any true solipsist.   Not only would this mythical solipsist fail to understand the phrase 'community of selves', he or she would not understand anything you can come up with either.
v11: If your definition of a concept is based on the implicit usefulness of the definition (presumably the usefulness is the fruitfulness of the discussion which follows) then it cannot be said to be an arbitrary definition, and I agree that that is a valid way to proceed.   But if, when you claim to be defining reality, your definition is not to be based in any way on conventional usage of the word 'reality', why do you use that word to label what you are defining?   Why not claim instead that you are defining kuliszality, say, so that no one confuses it with the already existing concept of reality?

v10: The problem with solipsism isn't that it's contradictory (you will be unable to find any contradiction without recourse to sloppy informal reasoning) but that it's trivial.   Solipsism is no more interesting than matrix mathematics restricted to zero matrices.   But it is no less valid and logical for that.
v11: I think this illustrates a fundamental disagreement here between us, namely about the role of formalization of arguments.   You do not actually say that informal reasoning, by virtue of its informality, is sloppy reasoning, but I get the impression that 'sloppy' was just added for emphasis.
v11: I never claimed that the problem with solipsism is that it's contradictory   I chose my words very carefully.   Your response has made me wonder if I have gone to a lot of trouble for nothing.   You have read 'contradiction' into my words because contradiction is a purely formal criteria, sometimes described as the foundation stone of Formal Logic, but my description was more like that of conflict of form and content.   By 'conflict' here I mean something stronger than, say, in the example of a sign which reads 'Please Ignore This Notice', a sign which one can still comply with after reading it, although the initial reading of it was in conflict with the stated request.   The appropriate kind of example is a sign which is falsified or manifested as false in the act of being read, such as 'This is illegible' or 'You do not exist' or 'This sentence is meaningless.'   Thus I agree that solipsism is trivially false, although I fail to see how it is trivially so for you, with your emphasis on the purely formal.

v10: In fact, it is your informal top-down view which results in rampant contradiction.   By starting with arbitrary informal concepts and elevating them to the level of fact/reality, then going down to the fundamentals and building up reality on these fundamentals using formal reasoning … you end up with contradictory starting and ending positions.   This is a problem only because you accord them the same status.
v11: While I am familiar with talk of top-down and bottom-up approaches in some non-philosophical contexts, I have never used it in any philosophical context.   The only reason I can see why you have brought it up here is that you suppose that this is the way formal and informal logic are related.
v11: I have above, in this reply, given the metaphor of the different order in which the architect and the builder proceed.   The metaphor was not intended to suggest one ordering is being preferred over another, or even that one ordering was simply the complete reversal of the other.   Nevertheless, I fear you will jump to the wrong conclusion, so let me offer another metaphor, which also has been used in Philosophy: the growth from a germinating seed to a tree.   The seed starts near the surface of the earth and grows in two directions simultaneously, upwards to the sky and downwards into the earth.   As in the building metaphor, what is lower supports all that is higher, so that the vertical dimension represents the deductive order, the order in which things are supported by the argument.   But so long as the deductive ordering is clear, the order in which the argument unfolds does not have to be the same.   For reasons which would take too long to explain here, I believe that a philosophic argument must begin its unfolding in the middle.   (So far, I have only been able to explain these reasons using mathematical analogies.)

v10: In concrete terms, most philosophers assume that space and time physically exist.   They elevate the sensory impressions of space and time to the level of physical reality.   Then they run into problems when physicists build concepts of spacetime that contradict the naive sensory impressions.   If philosophers merely kept their arrogance in check, by not assuming that space and time are within their purview, and let physicists do all the work then everything would be fine.
v11: In this paragraph and the following one, which seems to be one long diatribe about the arrogance of philosophers, you seem to be so wildly wrong that I am probably misunderstanding you, but I have done my best to respond to what I think you may be trying to say.   It would help enormously if you could be more specific – e.g. give the names of some philosophers you have in mind.
v11: Historically, I think you have understood the situation the wrong way round.   It was the astonishing success of Newtonian mechanics over several centuries which led to the arrogance of physicists to consider their discipline to be the only one that really mattered.   What you describe as philosophers being arrogant was really philosophers being over-awed by physicists instead of sticking to their own insights.   Then, when physicists had to abandon peculiarly Newtonian notions such as absolute time and action at a distance, they started to dabble in Philosophy as if no worth while Philosophy had ever been done before.   (I suspect that what you call 'naive sensory impressions' are not in fact naive or intuitive, rather they are some counter-intuitive notions peculiar to Newtonian mechanics, which notions physicists have now abandoned.)   The last 100 years have seen a lot of these dabblers doing the philosophical equivalent of reinventing the wheel.   As Santayana put it, 'Those who ignore history are condemned to repeat it.'   Having all the knowledge of modern physics is not going to put you at an advantage over Plato when it comes to discussing Philosophy.   As for the philosophers you criticize for their arrogance, they should rather be pitied for their slavish attitude to the popular image of Science with a capital 'S' – there is always a time lag between the popular image of something and the reality.
GS: Let physicists do their work, and philosophers do theirs.   Physicists have no right to dictate to philosophers what they can or cannot discuss, any more than philosophers can dictate to physicists what observations they should be trying to make.   If physicists can do all the work, does that not mean that all other disciplines – Biology, History, etc. as well as Philosophy – are redundant?

v10: The unmitigated gall and arrogance of philosophers is easily proved.   My conception of metaphysics is as the field which lays the basis for science and physics through pure reasoning.   OTOH, the typical philosopher's conception of metaphysics is as the field which short-circuits all of science and physics!   Philosophers don't trust scientists who have had a lot more success than they have themselves.   The arrogance!   Incidentally, the philosopher's conception of metaphysics is nonsense since you can't short-circuit physics.   Even the existence of space and time (let alone their natures) aren't something you can prove by pure reasoning on naive sense impressions.
v11: Curiously, what you put forward as the correct view of metaphysics is much like the view of philosophers themselves in the period when Newtonian mechanics dominated physics.   This is explicitly true of empiricists such as Locke, but I don't think rationalists were necessarily so different.   You may seem to have more of a case in the 19th Century, but German Idealism, for instance, should be seen more as a reaction to check the arrogance of physicists.   None of them, as far as I know, ever claimed that all the problems of Physics would be settled, if only we focussed all our attention on Philosophy.   (Towards the end of the 19th Century, there were even people who believed that all the laws of physics would turn out to be reduceable to laws of Formal Logic!   Thus even formal logicians were wasting their time, they should be doing Physics.)
v11: So perhaps you could name some philosophers in the last three hundred years who have claimed that metaphysics can short-circuit all of science and physics.

v10: By the way, the only influence Descartes had on me was to develop a deep distaste for philosophy.   His reasoning is risible, was risible back when I was in high school.   It took a lot of discussion on philosophy to transmute my distaste from philosophy to philosophers. -- Richard Kulisz
v11: I was not talking about direct influence of Descartes on you.   One important reason for reading a philosopher like Descartes is to be faced with some philosophic idea which you never even knew you had, acquiring it from one's surrounding culture like the air one breathes.   Seeing it laid out in black and white can actually free one from being captivated by it.   And what you have written since I made that suggestion has demonstrated it to be truer than I ever imagined.   Your whole way of thinking, what you think you are trying to do, etc., has striking parallels with Descartes' philosophy.
v11: A couple of years ago I had to admit to myself that I had been mistaken in my dismissal of the way Descartes proceeded at the beginning of the third meditation – where he starts from his own (mental) existence and dredges up the idea of God from it (without actually describing this idea).   I was expecting a straightforward deductive connection, even though Descartes goes out of his way to get the reader to see it differently.   I now realize that I was arrogant to so readily jump to the conclusion that so careful a writer should have presented an argument which was so obviously flawed.   I hope you have the good grace to do likewise. -- Gerald Somerville