I did not read that text that way.
The "deceiver" does not cause the doubt but takes advantage of it. Doubt is the natural element of Reason. The idea that one is being mislead by appearances on purpose is not a promotion of the isolation of solipsism but points to the difficulty of thinking for oneself.
From that point of view, Descartes' answer may be too easy.

Then I suppose you can do away with the Evil Demon and simply treat doubt as the main issue here. I suppose I can rewrite the conclusion as follows:

A solipsist can never doubt, and live in a world full of certainty.
Therefore, in the presence of doubt knowledge is possible.
Hence, doubt is proof that an external world exists.

I suppose then this thread title should read:

An epistemological proof of the external world.

Does that sound better?

That works for me.
But i have to confess that I never got the solipsism thing. In any of its iterations.
I am probably the wrong person to ask. I simply do not understand the idea.

That works for me.
But i have to confess that I never got the solipsism thing. In any of its iterations.
I am probably the wrong person to ask. I simply do not understand the idea. — Valentinus

Well, to be honest this idea originated from my studies of Wittgenstein's Tractatus, mostly. In that the limits of my world are the limits of my language. This equates in some idealist sense, the world with the solipsist in a pantheistic sense. What results from this is that epistemically, one can expand the limits of one's world when confronted with doubt, which is impossible for a solipsist. Hence, doubt, contra certainty, is what allows one to overcome one's limitations in the world.

Hope that made sense.

That does make sense.
I will have to mull upon it.

Renamed the thread. Hope others might find interest in it.

What results from this is that epistemically, one can expand the limits of one's world when confronted with doubt, which is impossible for a solipsist. — Wallows

Why would that be impossible for the solipsist? I mean wouldn't just the same restriction apply to new experiences?

Why would that be impossible for the solipsist? I mean wouldn't just the same restriction apply to new experiences? — Janus

Because epistemically, the solipsist is one and the same with the 'world'... I don't think there's much confusion about that statement, or not?

Why would there be any more difficulty for the solipsist in "expanding the limits of one's world" than in having new experiences?

Why would there be any more difficulty in "expanding the limits of one's world" than in having new experiences? — Janus

I don't understand. The point I am making can be thought analogously to a dream where a person self is in play and experiences are synthetically conjured up, in a solipsistic world that is finite. Does that make any sense?

I'm still not getting it. The dream horizon, just like the world horizon, can always be expanded, which in the dream context would be "expanding the limits of one's (dream) world" or having dreams (experiences) one has never had before.

[1]A solipsist can never doubt, and live in a world full of certainty.
[2]Therefore, in the presence of doubt knowledge is possible.
[3]Hence, doubt is proof that an external world exists. — Wallows

I disagree despite not being a solipsist.
I accept 1).
2) The question here is what is "knowledge". I assumed it to be something along the lines of "the improvement of certainty". However I don't see why this is evidently given without further assumptions. Lets say the Self investigates a certain part of itself to increase it's knowledge of that part. This partial improvement seems possible with your conception. However there is no guarantee that while increasing the certainty in one domain by amount x there isn't a loss in (an) other domain(s) that adds up to the amount x. This would obviously lead it to be a zero sum game overall and only a shifting of certainty of different parts. To prevent this you would have to assume something along the lines that there is a net gain over time. I don't see any basis for that.
However lets assume this to be the case to look at 3)

3) I don't see/understand how the external world enters into this at all. Lets say the Self increases knowledge there is no reason why a solipsist couldn't just call this an improvement of the knowledge of the Self by the Self (since everything in this view is part of the self). Therefore gaining knowledge/certainty does not necessarily refer to an increase of knowledge of an external world and can not prove the existence of an external world.
This can be illustrated if you imagine an incompetent god that by accident creates the universe. After this god investigates said universe and improves his/her knowledge of it. There is no reason to conclude from that, that there has to be something outside of that universe.

Btw I think the approach of Fichte is interesting. His basic question is why is the "illusion" so consistent and strongly present. The approach he takes is investigating fundamentaly necessary structures/properties of the self with this. However this is only vaguely related.

Btw2. My approach is the idea of change being a necessary condition for the self preceding it. The self experiencing change requires it to change itself. On this basis in my opinion one can view change as external factor that the self has to obied by. I am aware of the fact that a solipsist could state that the self is necessary for change like change is necessary for the self. However I view it as unequal pairing since at least in principle one can imagine change without a self but not a self without change. (Since there would be no possibility to have experiences without change.)
However I don't want to divert further from your actual point I just thought it might be interesting to you.

I'm still not getting it. The dream horizon, just like the world horizon, can always be expanded, which in the dream context would be "expanding the limits of one's (dream) world" or having experience one has never had before. — Janus

Yes, the world horizon or what Wittgenstein calls the limits of one's world is expanded by the process of doubting. Now, how can a solipsist doubt if they live in a 'world' where everything is the same as the self?

Now, how can a solipsist doubt if they live in a 'world' where everything is the same as the self? — Wallows

If everything is the self and the solipsist can have new experiences, then she has not experienced all of her self in which case she is never omniscient and so there would be room for doubt, no?

2) The question here is what is "knowledge". I assumed it to be something along the lines of "the improvement of certainty". — CaZaNOx

I don't think there are degrees of certainty. It's a binary situation here, or at least for the sake of this thread, epistemic closure is guaranteed for the solipsist. Since the solipsist is one and the same with the world, then there's nothing to doubt, yes?

To prevent this you would have to assume something along the lines that there is a net gain over time. I don't see any basis for that. — CaZaNOx

I don't see/understand how the external world enters into this at all. Lets say the Self increases knowledge there is no reason why a solipsist coukdn't just call this an improvement of the knowledge of the Self by the Self (since everything in this view is part of the self). Therefore gaining knowledge/certainty does not necessarily refer to an increase of knowledge of an external world and can not prove the existence of an external world. — CaZaNOx

Well, just take the most popular book in the world, being the Bible. (Keep in mind that God, literally is the ultimate solipsist). S/He/It created us in his own image. While is this sort of irrelevant, I suppose it can be an interested corollary to the topic.

If everything is the self and the solipsist can have new experiences, then she has not experienced all of her self in which case she is never omniscient and so there would be room for doubt, no? — Janus

I don't think that the solipsist can experience genuinely new experiences. The boundary between doubt and certainty is rather explicit for a solipsist, which I assume you don't agree with here?

I don't think that the solipsist can experience genuinely new experiences. The boundary between doubt and certainty is rather explicit for a solipsist, which I assume you don't agree with here? — Wallows

I'm not sure what you mean by "genuinely new experiences". Anything you experience which you haven't experienced before is a new experience, isn't it? There is a sense in which everything you experience is a new experience, because everything that happens is unique and unrepeatable.

Can you explain what you mean by the boundary between doubt and certainty being "rather explicit for a solipsist"? I mean if the world was nothing but you, and you knew yourself exhaustively, there would be nothing but certainty, would there? Or do you think it would be possible, assuming that the world is nothing but you, that there could be any doubt at all, in that case, that the world is nothing but yourself?

Anything you experience which you haven't experienced before is a new experience, isn't it? — Janus

Isn't that a metaphysical claim? I believe Wittgenstein addressed this issue of private experiences or some such in the Investigations with his Private Language Argument.

I don't see how it would be anything more than what is entailed by the definitions of 'new' and 'experience'.

Can you explain what you mean by the boundary between doubt and certainty being "rather explicit for a solipsist"? I mean if the world was nothing but you, and you knew yourself exhaustively, there would be nothing but certainty, would there? — Janus

Yes, I'm glad we are on the same page finally...

Or do you think it would be possible, assuming that the world is nothing but you, that there could be any doubt at all, in that case, that the world is nothing but yourself? — Janus

What do you mean?

Or do you think it would be possible, assuming that the world is nothing but you, that there could be any doubt at all, in that case, that the world is nothing but yourself? — Janus


What do you mean? — Wallows

I was just leaving open the possibility that you might not agree with the first two sentences, but you said you are glad we are on the same page, so apparently you do agree with them. The problem then is that I am never certain what will happen next, so there is apparently not "nothing but certainty" in which case solipsism is already refuted by the possibility of (unpredictable) new experiences.

As an example the fact that I am speaking to you, and have no idea what you will say next refutes solipsism on this criterion, and I would also say this applies equally to the dream world as it does to the waking world.

I can counter this by providing the 'Will'. In a dream where one is cognizant that one is dreaming, everything that happens is dictated by a sense of 'willpower' of the subject imposed on the happenings of the dream (now fully realized as one and the same). I haven't come across a better analogy to think of that would reflect the sentiments of this line of reasoning/thread.

You seem to be speaking about so-called lucid dreaming. I have never experienced that, so I can't comment. But if you can dream and not be cognizant that you are dreaming, then you are not omniscient, which again means there is room for doubt.

You seem to be speaking about so-called lucid dreaming. — Janus

Yeah, pretty much.

But if you can dream and not be cognizant that you are dreaming, then you are not omniscient, which again means there is room for doubt. — Janus

About how every one of us goes about in life, I suppose.

Yep!

Are there any unanswered questions in your mind about epistemic solipsism and how it can be countered by doubt leading to the conclusion that if a person can doubt then that "experience" is grounds for proving the existence of an external world?

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'. — Wallows

This can be gotten around by defining solipsism a certain way. First of all, the self is just another experience. For the solipsist, all that exists is the experiences a solipsist has. There is no hidden self generating the experiences of a world.

In addition, doubt is just one more kind of experience. Also, the solipsist can doubt because they do have experiences of what appears to be an external world full of other people. Remember that solipsism is a philosophical position that only comes about through inquiry and taking skepticism to its logical conclusion. Nobody is a solipsist by default.

What solipsism is supposed to do is to provide a certain philosophical outlook based on only the experiences a solipsist has and nothing else. It's actually a response to radical skepticism. But just because the position is certain doesn't mean that the solipsist can't doubt the truth of solipsism. After-all, experience appears to be otherwise, and you have all these people in those experiences criticizing and mocking the position.

As for new knowledge, it's just another experience. The question is why is there a stream of experiences if nothing is causing them? There's no more answer to that than why anything exists.

I don't see why there wouldn't be the same problems with a binary notion of certainty.
I further don't see why there should be nothing to doubt or what you are appling this to.
The main thrust of my argument im 2) was that there are parts that you can have knowledge of. To me this seems indicated by your wording of 1).

I would put it this way either their is a single domain (the entire self) to which one ascribes could ascribe certainty or there is a multitude of domains to which certainty can be attributed to. This second notion could also include the entire self.

If we look at descartes cogito (ergo) sum (I think, (therefore) I am) one can see that certainty is ascribed to ones existance. In other words even if the self knows nothing else the self is certain of it's own existence. 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.

I would therefore basically refuse that because the solipist is one with the world there is nothing to doubt. It evaluates different aspects differently the "Existence" as such is not doubted however any ascribed property is.

I don't see how you address my criticism regarding 3).
I basically suggested the analogy with god because he as you pointed out he/she seems to be the ultimate solipsts. His having a certain knowledge of the world(or not) doesn't shows or lead to concludimg that there is somethimg outside. Do you agree?

This can be gotten around by defining solipsism a certain way. — Marchesk

True, but, imposing a stipulative definition on a generic one to make the logic fit is basically cheating. I use solipsism not stipulatively here...

First of all, the self is just another experience. — Marchesk

The self is the only experience a solipsist can attest to being true. Again, there is no ordinary 'world' in the "world" of the solipsist.

For the solipsist, all that exists is the experiences a solipsist has. — Marchesk

Yes.

There is no hidden self generating the experiences of a world. — Marchesk

Arguably, yes, although that issue is addressed in the Uppinshads and Bhagavad Gita.

In addition, doubt is just one more kind of experience. — Marchesk

Not true. Doubt is the only experience that is genuine here. Everything else in a solipsistic 'world' are what Wittgenstein might call tautologies.

Also, the solipsist can doubt because they do have experiences of what appears to be an external world full of other people. — Marchesk

Then, that wouldn't make them solipsists.

Remember that solipsism is a philosophical position that only comes about through inquiry and taking skepticism to its logical conclusion. Nobody is a solipsist by default. — Marchesk

Not only that; but, solipsism is an extreme form of idealism. And, I contest here, just for the sake of argument, that the entity we call 'God' is de facto the only true solipsist.

As for new knowledge, it's just another experience. The question is why is there a stream of experiences if nothing is causing them? There's no more answer to that than why anything exists. — Marchesk

Not the same kind-of experience as that of living in a solipsistic world...