OK, before we agree, I wanted to raise the issue of 'domains' with @Janus but, was too busy trying to reach some common ground...

The point with domains, is that the experience of the domain or 'world' of the solipsist is truth apt from within the world, and not by analysis wrt. to other domains. To try and phrase this abstract issue another way, if I and you spoke different languages, then we could only reach a common understanding through the use of ostensive definitions, which we could point at and say that 'grue' is the same thing as my 'water' while pointing at a glass or pouch full of water.

What am I getting at here? Well, the point in my mind is that domains that are non-truth apt (a common criterion cannot be achieved), such as the stuff that Wittgenstein talked about private pains or private languages, are non-nonsensical within language and must be shown. Perhaps @Banno can help out here.

The key conclusion is that a self that is purley based on doubt can not doubt itself at it's core. This view simultainously asserts that there seem to be other domains, being part of the self, that can be doubted. So the self would have only uncertainties no matter what is in question exept it's own existence. — CaZaNOx

And, this is why solipsism was/is (at least in my mind) thought of as a valid idea that one can hold, what cannot be doubted is the fact that one is doubting, within the domain of the self.

Why can't a solipsist doubt? The answer to that question is crucial to your argument, right?

A solipsist cannot doubt because they are trapped in their own world. Epistemically closed off, hermetically sealed, thus doubt cannot arise because it is the opposite of what a solipsist experiences, supreme certainty.

I am struggling with the remarks especially in your first response. Not with the content but with the relevance to the issue at hand.

the experience of the domain or 'world' of the solipsist is truth apt from within the world, and not by analysis wrt. to other domains. — Wallows

I first want to emphasize the word expierience (1) to refere to it later in my reply.

I agree that the world is not truth apt wrt. other (external) domains. This would just be misunderstanding the solipsistic viewpoint. It rather has to be as you state that it is truth apt from within.

However what seems to me especially problematic is

if I and you spoke different languages — Wallows

Lets ignore the language the other speaks and focus, from the solipsitc perspective, on the notion of there being a language at all. The key point of an (internal) language is that it names different things differently in order to conceptualize the world from within. This however needs as precondition different things/domains that are worth distinguishing from within. This analogy seems completley missplaced if one understands the solipsistic perspective to only contain one domain (the self/world of the solipsist).

Now I see no reason why a solipsist couldn't in general state that existence necessarily is given despite there being doubt because of him experiencing at all. However negate any content of his experience/statement formulated by his internal language and therefore it's validity. This could also be applied to doubt that can be understood as reasoning with/applying the internal language, that can be faulty. Therefore in principle doubting itself as process could be entirely misguided in framing the doubt. Further any attempt to state what one is doing could be misguided, including doubting itself. I obviously agree that from an outside perspective one could form that statement but not from within.

I want to point this out by referring back to experience(1).
I wrote

If we look at descartes cogito (ergo) sum (I think, (therefore) I am) — CaZaNOx

The key points for entering the brackets is that with the brackets we are applying a coherent language with coherent logical conclusions. This is not the case for the solipsist at all. For him it is somehow a experience in which he by thinking/doing sth.(whatever this is) he experiences sth. Where the experience contains the manifestation of existence of the self at a fundamental level. However in form of experience there doesn't have to be any proper realization of this as we framed it with our coherent use of language from the outside. As you surely know at this point of his work descartes already negated the conceptualizing a triangle as thing with three angles. The solipsist so to speak seems to be in an phenomenological hole where all he has is incoherent experiences. (I don't know how clear I made this point?)

However what I completely fail to grasp is why and how any of this things should refer at all to the existence of an outside world at all. Even if we assume the solipsist to be at a way better place then the self that is doubting in descartes meditations f.e. based on an approach similar to Fichte that based on experiencing consistency infers consistency that has to be explained by a certain necessary internal structure, allowing somewhat proper internal language.
This I think as you would agree leads to an axiomatic system where there is no doubt and only deductive proofs that are certain in said system. However the certainty of the axiomatic system itself build by the self is not free of doubt. Because the chosen axioms by the self are open to doubt as descartes showed. There is no reason why different solipsitic positions couldn't build different axiomatic systems or why a self couldn't swap between them if they build this system at all.
In terms of language, because the language is so to say only internal the meaning of the words would be certain. However this doesn't exclude the possibility of inventing a new language from scratch.

A solipsistic position could for example include the necessary experience of doubt. We could even translate this to conceptualizing death(as we understand it) to mean in solipsism an expierience of doubt that leads to a complete new language/axiomatic system after death. This obviously would have to be reasoned by the current language logic used by the solipsist. However I really want to emphasize again my overarching core question. Where is the pointer to an external world in this at all?

Where is the pointer to an external world in this at all? — CaZaNOx

Sorry that I can't address the entirety of your post, given my limitations here.

The point with the domains analogy was that the solipsist can only doubt if and only if there is something more than the self of the solipsist in existence. Hypothetically, we can assert that the solipsist lives in a world that only is immediately knowable to the solipsist and not other.

Thus, my post about domains of discourse and the like. Let me know if that helps.

the solipsist can only doubt if and only if there is something more than the self of the solipsist in existence. — Wallows

Why can he just assume incoherence of his reasoning process or axioms or words used.
Or why can't we conceptualize the solipsist simply as having expieriences of incoherence.

In other words don't you need specific assumptions to justify your iff.

You seem to say that doubt necessitates external initators, however the loosing of consistency or coherence can be thought of as internal initators of doubt that can in principle be build into the self. In the analogy of death I used above: death as internal shortcoming/necessary-process/change from within without conceptualizing external factors that lead to death (this case gets clearer if a solipsistic position doesn't necessarily postulate a material body that could be subject to external forces.)

In other words don't you need specific assumptions to justify your iff. — CaZaNOx

In the analogy of death I used above: death as internal shortcoming/necessary process change from within without conceptualizing external factors that lead to death (this case gets clearer if a solipsistic position doesn't necessarily postulate a material body that could be subject to external forces.) — CaZaNOx

Yes, you're on point here. These conditions are multifaceted in the Tractatus. Spinoza's pantheism and necessitarianism, Schopenhauer's theoretical egotism, Kant's Transcendental Idealism all contribute to the conditions allowing Wittgenstein to postulate such an entity as novel and unheard of until its publication. Mind you, even in his Investigations I don't believe he repudiated the notion of a hypothetical solipsist. This line of thought continues into his latter philosophy presented in On Certainty.

Here is P.M.S Hacker on this solipsism present in the Tractatus:

What the solipsist means, and is correct in thinking, is that the world and life are one, that man is the microcosm, that I am my world. These equations... express a doctrine which I shall call Transcendental Solipsism. They involve a belief in the transcendental ideality of time. ... Wittgenstein thought that his transcendental idealist doctrines, though profoundly important, are literally inexpressible.

— Hacker, Insight and Illusion, op cit., n. 3, pp. 99-100.

So, I'm going to polish up everything I have stated thus far.

1) A solipsist lives in a world full of certainty.
2) Epistemologically, Cogito ergo Sum, ergo, a solipsist self is one and the same with the world, leaving no room for doubt in such a world.
3) A solipsist cannot doubt and live in a world full of certainty.
4) Where doubt arises, the world is not solipsistic.
5) Therefore doubt presupposes a world where epistemologically one can find out new facts or experiences about the world.
6) Hence, where doubt arises, the existence of an external world that is non-solipsistic is warranted to assume and/or conclude.

Therefore, if one can doubt when confronted with any skeptical argument, then that implies that knowledge is possible, and that we don't live in a solipsistic world. — Wallows

I don't see how that follows. If your belief that the external material world existed was false then you wouldn't be able to have doubts and knowledge would be impossible?

Well, the ability to learn more, establish norms, and do all sorts of things would be moot for a solipsistic being that lives in a world full of certainty. Yes?

Yes. So what?

I don't see how this is a response to my objection.

If your belief that the external material world existed was false then you wouldn't be able to have doubts and knowledge would be impossible? — GodlessGirl

It could not be proven false in the same way the set of all sets cannot contain itself. Or another way to frame the issue is if you were born in a coma and lived in a dreamless world, since dreams attain their ontological significance from the waking world.

You are contradicting yourself. Before you asserted that belief in the external material world was warranted and now you are saying it cannot be proven false.

In order to know something you have to know that the contrary is impossible.

How could you justifiy your belief in the external material world without begging the question?

Before you asserted that belief in the external material world was warranted and now you are saying it cannot be proven false. — GodlessGirl

Well, yes just as the fact that I am doubting cannot be proven false or analogously the cogito ergo sum entails that existence is a prerequisite for the statement to even be plausible. Conversely what would the contrapositive even mean in that case?

In order to know something you have to know that the contrary is impossible. — GodlessGirl

I think I laid out my thoughts about this with the above.

How could you justifiy your belief in the external material world without begging the question? — GodlessGirl

I'm not quite on the same page, can you elaborate, please?

Well, yes just as the fact that I am doubting cannot be proven false or analogously the cogito ergo sum entails that existence is a prerequisite for the statement to even be plausible. Conversely what would the contrapositive even mean in that case? — Wallows

You seem to be strawmanning me. I am not proposing a contrapositive for your belief that you exist and doubt. I am saying you do not have justification that the external material world exists. There is no observation that is inconsistent with Descarte's demon being the case.

I am saying you do not have justification that the external material world exists. — GodlessGirl

Therefore solipsism or a brain in vat? No, I already expanded on the fact that doubt epistemically presupposes that one is not a solipsist, and hence the external world exists.

Doubt doesn't presuppose you aren't a solipsist. You could be in the matrix and be doubting things right?

Doubt doesn't presuppose you aren't a solipsist. — GodlessGirl

I'm convinced it does. Here it is again in standard form:

A solipsist is one and the same with his or her own world.
Epistemically the solipsist lives in absolute certainty.
A solipsist cannot doubt and live in absolute certainty at the same time.
Therefore, where doubt arises, there is more to the world of a solipsist than only their self in it.

What are you saying the solipsist is certain of what? That they exist? That doubt exists? So what? That doesn't mean they are certain that they aren't in the matrix.

It could be said that there is more to the self that one's knowledge of the self at a particular time.

As an analogy, if you consider that a lucid dream stems from a self, then there are things you can doubt within a lucid dream, but that doesn't imply in itself that the lucid dream stems from something outside the self. Then continuing with that analogy, to a solipsist everything is a lucid dream, so doubt doesn't imply something outside the self, but only that the self doesn't know itself completely.

We don't have to assume that the self would have to know everything about itself. Then it's a matter of interpretation whether we see the unknown as something separate from the self or as an unexplored part of the self.

A limitation in this kind of discussion is that our language and concepts stem from what we experience, so for instance the very concept of doubt stems from our experiences, and then if you assume that doubt cannot exist if there is only a self then you conclude that there is something separate from the self, but if you assume that doubt is a normal part of the self then it doesn't follow that there is something separate from it.

It could be said that there is more to the self that one's knowledge of the self at a particular time. — leo

Yes, and that is an issue worth exploring. The self as we know it in today's Western pop-psy lingo is composed of an ego-ID-and super-ego. I have a very small ego, infinitesimally haha. The continentals have exalted the ego to the point of arriving at postmodernism and the like. Yeah, a lot can be said here.

As an analogy, if you consider that a lucid dream stems from a self, then there are things you can doubt within a lucid dream, but that doesn't imply in itself that the lucid dream stems from something outside the self. Then continuing with that analogy, to a solipsist everything is a lucid dream, so doubt doesn't imply something outside the self, but only that the self doesn't know itself completely. — leo

Well, you might be taking the analogy too far. I suppose the point is that in a word where only the self exists, there is absolute certainty. Perhaps the ID is Satan, the ego Jesus, and the super-ego God?

A limitation in this kind of discussion is that our language and concepts stem from what we experience, so for instance the very concept of doubt stems from our experiences, and then if you assume that doubt cannot exist if there is only a self then you conclude that there is something separate from the self, but if you assume that doubt is a normal part of the self then it doesn't follow that there is something separate from it. — leo

Yes, go on, what do you mean by something separate from the self?

Yes, go on, what do you mean by something separate from the self? — Wallows

Something that is not the self. If there is only self then there is nothing that is not self, nothing separate from it, nothing independent of it, nothing outside it. If there is only self everything is part of it, everything is connected.

If there are two parts of the self that seem always disconnected, then we could say that the self has not managed to see the connection, or we could say that there is something besides the self.

We could see all of us as part of one self, seemingly disconnected, but connected in a way we have not quite uncovered yet.

Sorry, I totally missed your post...

The difference between the matrix and a solipsist is in that the matrix still engendered the idea of separate selves in the simulation. Which, is fundamentally different than the world view of the solipsist.

We could see all of us as part of one self, seemingly disconnected, but connected in a way we have not quite uncovered yet. — leo

Yeah, this is pretty much the starting point for any form of spiritualism. Yet, the solipsist is a fictional God if you can extrapolate from what I've been preaching.

First off I dont even understand how you get from "thoughts exist therefore a self exists" What is the self? What is there besides the thoughts and experience? You assert there is something else but what is it? Maybe it's the case that just the thoughts exist.

We might be talking past each other with solipsism. I just mean the position that you can never know if any other minds or a material world exist. I dont see an argument for being able to know Descartes demon doesn't exist.

I'm planning on writing a paper soon about the relationship between epistemological solipsism and using it as an ad hoc proof that knowledge is possible. I'm looking for some feedback or how to shape these loose ends into something coherent.

A while back I come to the conclusion that for any solipsist inhabiting a 'world', that solipsist cannot doubt. One of the implications of such a hinge proposition is that if a man or woman were presented with Descartes Evil Demon, which prods the fictional Job or what have you to doubt, then the very process of doubting cannot be doubted itself implying that the doubting of the evil demon is proof that the person is not living in a hermetically sealed off world of their own (brain in vat)/(solipsism).

Therefore, if one can doubt when confronted with any skeptical argument, then that implies that knowledge is possible, and that we don't live in a solipsistic world.

Let me expand on this idea of epistemological solipsism. The world of the solipsist is one and the same with the self of the solipsist. What does this mean? It means that doubt cannot arise, because the world of the solipsist is full of certainty. To present this issue another way, epistemologically the solipsist is hermetically sealed off from anything beyond what constitutes their 'world'.

That's about the gist of it.

Main points:

Descartes Evil Demon causes an individual to doubt.
A solipsist can never doubt, and live in a world full of certainty.
Therefore, in the presence of doubt knowledge is possible.
Hence, the Evil Demon's prodding to doubt is proof that an external world exists. — Wallows

Yet another "Huh?" response from me. A lot of what you wrote seems bewildering to me.

The first question, I suppose, is why are you conflating solipsism and whether knowledge is possible? They're not the same thing.

First off I dont even understand how you get from "thoughts exist therefore a self exists" What is the self? — GodlessGirl

I don't know if you're being facetious or not. The self of course exists, otherwise who's talking here?

Yet another "Huh?" response from me. A lot of what you wrote seems bewildering to me. — Terrapin Station

Then address the following if you will:

A solipsist is one and the same with his or her own world.
Epistemically the solipsist lives in absolute certainty.
A solipsist cannot doubt and live in absolute certainty at the same time.
Therefore, where doubt arises, there is more to the world of a solipsist than only their self in it.

The first question, I suppose, is why are you conflating solipsism and whether knowledge is possible? — Terrapin Station

I'm using solipsism as a template to compare an entity to that which a fictional entity might assume to have knowledge about in an absolute manner. Given that a solipsist is tantamount to being a godlike entity, I then proceed to show that their omniscience of the world they inhabit, corresponds with a degree of knowledge that leave no room for doubt. Thus, where doubt is not possible, then that solipsistic world excludes the existence of other minds, or an outer world apart from one's own self. Therefore, where doubt is possible, then that would validate, through contradiction of the previous, the idea that there exist other minds or an external world.

Epistemically the solipsist lives in absolute certainty. — Wallows

That's not a tenet of solipsism and it doesn't follow from anything. Consider thoughts you have, things you imagine, ways you feel, etc. Aren't they sometimes vague/uncertain for you?