You are viewing the historical archive of The Philosophy Forum.
For current discussions, visit the live forum.
Go to live forum

Disproving solipsism

frank November 17, 2025 at 23:26 3100 views 81 comments
'You can disprove everybody else's solipsism, but you can't disprove it to yourself.'. -- Searle

And because you can't disprove it to yourself, I can't persuade you to reject it. This is because argumentation has as its goal a meeting of the minds.

This state of affairs shows that mental states are enjoyed in isolation. By this I don't mean they're private in the Wittgensteinian sense, but rather that there appears to be clear boundaries between what I'll call minds.

Thoughts?

Comments (81)

Outlander November 17, 2025 at 23:36 #1025493
Isn't this one of those things that—while seemingly deep—actually has no effect at all? Like, what if there really is a Firmament above Earth? Are you reasonably, in your lifetime, ever going to be rich enough or permitted by a government to leave the atmosphere and colonize another planet? No? Then why worry about it? What does any of it matter? "Oh it's just such a profound difference between what I thought was reality versus what it actually is!" Oh please. Don't give me that. No it's not. This is basically the same thing as the "monster under the bed that disappears every time you check but only for as long as you're checking" argument. What if your actually the legitimate heir to the throne of England? No one will believe you. And thus, nothing will come of it. So, a non-issue remains exactly that. A non-issue. Save for those who have an abundance of such, I'd wager. :smirk:
frank November 18, 2025 at 00:06 #1025499
Reply to Outlander
Anglo-American philosophy has been stranded for some time in an attempted pivot away from Cartesian dualism. The OP is pestering the issue anew.

You could probably find a forum focused on welding if the OP question seems like a waste of your time. :grin:
T_Clark November 18, 2025 at 00:16 #1025502
Quoting frank
And because you can't disprove it to yourself, I can't persuade you to reject it.


Solipsism as usually understood is not something that can be verified or falsified empirically. It’s metaphysics. It’s something you can pretend to believe because it makes figuring things out easier.

Quoting frank

…This is because argumentation has as it's goal a meeting of the minds.

This state of affairs shows that mental states are enjoyed in isolation. By this I don't mean they're private in the Wittgensteinian sense, but rather that there appears to be clear boundaries between what I'll call minds.


Just because I cannot experience what you experience directly does not mean there isn’t a connection. You are right though, what connection there is is not clear or direct.


frank November 18, 2025 at 00:21 #1025503
Quoting T Clark
Solipsism as usually understood is not something that can be verified or falsified empirically. It’s metaphysics. It’s something you can pretend to believe because it makes figuring things out easier.


If you're up for it, I'd like to try to persuade you that solipsism is wrong. I just need for you to play devil's advocate and defend it. Ok?
Colo Millz November 18, 2025 at 00:27 #1025507
Reply to Outlander It matters - greatly. There is a huge and mighty choice between solipsism and idealism and choosing to dip your feet into the real world.
T_Clark November 18, 2025 at 00:28 #1025508
Quoting frank
If you're up for it, I'd like to try to persuade you that solipsism is wrong. I just need for you to play devil's advocate and defend it. Ok?


Let’s take a shot at it.
Colo Millz November 18, 2025 at 00:30 #1025509
Quoting T Clark
Just because I cannot experience what you experience directly does not mean there isn’t a connection. You are right though, what connection there is is not clear or direct.


The connection is the verification of certain rules which must apply or not apply. If this verification were merely private, it would be empty. Rule making by definition is public.
Colo Millz November 18, 2025 at 00:31 #1025510
If language were truly solipsistic it would be rpoqi3 u4r[p 09aWDDAJKDHL AKjhdliJKA HLUHLIUHLIE UFGNZ
Outlander November 18, 2025 at 00:38 #1025512
Quoting frank
Anglo-American philosophy has been stranded for some time in an attempted pivot away from Cartesian dualism. The OP is pestering the issue anew.

You could probably find a forum focused on welding if the OP question seems like a waste of your time. :grin:


I find most people who become entrapped in the belief that "nothing is real" that is to say "other people aren't real" do not appreciate the philosophical depths of true solipsism and are simply struggling with something quite non-philosophical and dangerous to themselves and those around them, is all.

It's a fine topic. For the few whom it actually applies to.

Quoting Colo Millz
There is a huge and mighty choice between solipsism and idealism and choosing to dip your feet into the real world.


This seems to disregard the main tenets of solipsism. It's not a "choice." It's literally the real world. That is to say, what you, or to your credit, any normal person would consider "dipping [their] feet into the real world" is doing the exact opposite. It's derived from a tale in Greek mythology (or perhaps the mythology was derived from an actual worldview) where a mortal is damned to live an eternity alone, all while thinking he's in a world full of innumerable other persons, thus making it an ever more vindictive punishment than if he was perceptively alone and sure of his or her fate. Again, it's a line of thought best avoided altogether. Particularly for those susceptible to the wills and minds of others.

Also, @frank this is what I'm talking about. Most people who believe "other people aren't real" (or sure, the deeper tenet that is, nothing except myself and my thoughts can be "proven" as real) really don't understand anything about the deeper philosophy, only the immediate descriptor (or in my view, symptom).
180 Proof November 18, 2025 at 00:40 #1025513
Reply to frank Searle's tongue was in his cheek: whoever "disproves everybody else's solipsism" presupposes that s/he is not a solipsist. :smirk:
Colo Millz November 18, 2025 at 00:43 #1025514
Quoting Outlander
It's not a "choice." It's literally the real world.


Yes. It is bound to be what we receive, all right. It is nothing to do with choice.

But we can nevertheless choose to receive - or not - certain facts.

One fact is that of rule-following.

That fact means that I cannot check, given the data of 104987098upeoih f mn , lkjhpojhoj hpao hpoiAHPO certain subjective elements - if I check only subjective elements that means that statement remains meaningless.

If i follow a rule, it has to be public - by definition. That is what a rule is.
frank November 18, 2025 at 00:49 #1025516
Quoting T Clark
Let’s take a shot at it.


Ok thanks! Shot number 1:

Doesn't your solipsistic view conflict with your everyday behavior? For instance, you talk to me without knowing what I'm going to say next. How could that behavior fit with solipsism?
frank November 18, 2025 at 00:52 #1025519
Quoting 180 Proof
Searle's tongue was in his cheek: whoever "disproves everybody else's solipsism" presupposes that s/he is not a solipsist. :smirk:


Does it? How so?
T_Clark November 18, 2025 at 02:19 #1025531
Quoting frank
Doesn't your solipsistic view conflict with your everyday behavior? For instance, you talk to me without knowing what I'm going to say next. How could that behavior fit with solipsism?


Your existence might be an hallucination, a dream, an illusion, a brain aneurysm, psychosis, my imagination. Maybe I got lonely. I stole the following from a post I made many years ago.

One of the Hindu gods was sitting around, lonely. For company, he made himself forget he was god, and split himself into many parts. Maybe I’m God. I have this image of god behind the stage in a puppet theater that includes everything. He plays all the parts, speaks all the parts.

I’m not tossing this out just to be difficult. If I am the only thing that exists, it’s doubtful I would take any doubts I had about the existence of a real world outside myself seriously. Why would my lonely, isolated reality behave the way you think it should here in this purported reality.




T_Clark November 18, 2025 at 02:27 #1025535
Quoting Colo Millz
The connection is the verification of certain rules which must apply or not apply. If this verification were merely private, it would be empty. Rule making by definition is public.


I’m not sure whether the problem is with @frank’s comment or my response… As I think about it more, I think it was my response that was incorrect. See my response to @frank’s response immediately above this one.
frank November 18, 2025 at 02:28 #1025536
Reply to T Clark That same image came to me once: of God with finger puppets, doing a puppet show for herself. Bloody puppet show. :scream:

So your answer is that everything is you, but parts of you are not available to consciousness right now?

T_Clark November 18, 2025 at 02:30 #1025537
Quoting frank
So your answer is that everything is you, but parts of you are no available to consciousness right now?


Sure. It might not even be possible for them to become conscious. Who knows how my isolated super brain might work.
frank November 18, 2025 at 02:49 #1025539
Quoting T Clark
Who knows how my isolated super brain might work.


Surely some part of you knows how it works? Your personal Lord of Illusion?
frank November 18, 2025 at 02:50 #1025540
Reply to Colo Millz
Are you familiar with Kripke's argument that meaning can't arise from rule following?
T_Clark November 18, 2025 at 03:14 #1025542
Quoting frank
Surely some part of you knows how it works? Your personal Lord of Illusion?


I have some idea how my mind works in this, our purported reality. But that knowledge is based on my experience and understanding that my mind is connected with an outside world and other people.
T_Clark November 18, 2025 at 03:16 #1025543
Quoting frank
Surely some part of you knows how it works? Your personal Lord of Illusion?


What would be going on in your mind if you had been cut off from all physical and social experience since you were born.
ProtagoranSocratist November 19, 2025 at 19:34 #1025786
There really is no way of knowing whether or not you are just a product of my imagination...
Paine November 19, 2025 at 20:15 #1025794
Reply to ProtagoranSocratist
Well, Kant put the "not knowing" the other way around. Here is the Theorem from the Refutation of Idealism:

Quoting Critique of Pure Reason, B275
The mere, but empirically determined, consciousness of my own
existence proves the existence of objects in space outside me.


Same ignorance, different day.
frank November 19, 2025 at 20:18 #1025796
Reply to Paine
Excellent. Why don't you flesh out Kant's argument for us?
Paine November 19, 2025 at 20:49 #1025803
Reply to frank
The Introduction written by Guyer and Wood in the linked edition is the clearest summary (and limits to summary) that I have found. Kant developed his view over many years.

For this discussion of solipsism, I suggest reading the Refutation of Idealism from B275 to B288 in the linked text. It reflects much of the previous part of the book while also trying to sharpen his use of terms.

I will do my best to answer any questions from that common ground.
ProtagoranSocratist November 19, 2025 at 20:49 #1025804
Quoting Paine
Same ignorance, different day.


I was just trying to interject some harmless fun into the conversation.
frank November 19, 2025 at 20:50 #1025805
Reply to Paine I don't think Kant's point is really all that complicated. Can you not encapsulate it?
Paine November 19, 2025 at 20:52 #1025806
Reply to ProtagoranSocratist
I was having fun, too. Maybe it was too culturally limited to my ruralism.
Paine November 19, 2025 at 21:07 #1025811
Reply to frank
We do not have access to an "I" as a given before our experience in the world. So, when we approach the matter as if that is not a critical feature of experience, we take on airs and imagine proximity to the divine.

But that is not all that Kant was trying to say. My summary may be correct and not very useful heard in isolation. Or it could be incorrect which also would require more work reading the text.
frank November 19, 2025 at 21:16 #1025813
Quoting Paine
Or it could be incorrect which also would require more work reading the text.


He's just saying that consciousness of my own existence requires something to compare and contrast with me. The use of dialectics runs through the CPR. This is a case of that.

Paine November 19, 2025 at 21:21 #1025814
Reply to frank
This is why I resisted giving a summary.

Perhaps you could provide references that support your interpretation. On the surface, your description does not account for the emphasis upon the intuitions of space and time.
frank November 19, 2025 at 21:25 #1025815
Quoting Paine
On the surface, your description does not account for the emphasis upon intuition of space and time.


Per Kant, we don't learn about space and time a posteriori. As for a reference, I don't think we can do better than Kant himself. Have you read the Transcendental Aesthetic?
Paine November 19, 2025 at 21:37 #1025818
Quoting frank
Per Kant, we don't learn about space and time a posteriori.


That is more of an argument toward accepting an "ontological" limit than saying:

Quoting frank
He's just saying that consciousness of my own existence requires something to compare and contrast with me. The use of dialectics runs through the CPR. This is a case of that.


The Refutation of Idealism section previously linked to argues against the "any difference will do" idea.





frank November 19, 2025 at 21:41 #1025820
Quoting Paine
Per Kant, we don't learn about space and time a posteriori.
— frank

That is a more of an argument toward accepting an "ontological" limit than saying:


I don't know what an ontological limit is. That we know about space and time a priori is the outcome of a series of arguments.

Quoting Paine
The Refutation of Idealism section previously linked to argues against the "any difference will do" idea.


I don't know what "any difference will do" refers to. It has nothing to do with anything I said.
Paine November 19, 2025 at 21:42 #1025821
Quoting frank
He's just saying that consciousness of my own existence requires something to compare and contrast with me. The use of dialectics runs through the CPR. This is a case of that.


frank November 19, 2025 at 21:49 #1025822
Quoting frank
He's just saying that consciousness of my own existence requires something to compare and contrast with me. The use of dialectics runs through the CPR. This is a case of that.


And?
Paine November 19, 2025 at 22:04 #1025826
Reply to frank
Since the intuitions are separated from the processes of reason a priori, differences of experience are neither what Descartes nor Berkeley described, as outlined in Kant's Refutation of Idealism.

That approach is different from observing there are "differences" of experience that provide a context for a subject as presented in Descartes and Berkeley. It is on the same grounds that Kant resisted Hume describing causality as only a story that is told.

frank November 19, 2025 at 22:29 #1025832
Quoting Paine
Since the intuitions are separated from the processes of reason a priori, differences of experience are neither what Descartes nor Berkeley described, as outlined in Kant's Refutation of Idealism.

That approach is different from observing there are "differences" of experience that provide a context for a subject as presented in Descartes and Berkeley. It is on the same grounds that Kant resisted Hume describing causality as only a story that is told.


I'm not sure what you're saying. Kant is basically arguing that consciousness of the self is generated by the mind's organization of experience according to a priori categories. You could put it this way: as the mind goes about organizing experience, it develops the concept of a unified world that allows the disparate elements to become meaningful. Each thing has the potential to be meaningful relative to this cohesive world. It's just part of the mechanics of this process that a proto-subject appears as a kind of logical entity. Who is having these experiences? It's me!

I'm a really non-linear thinker, so I'm struggling to explain this. But Kant is suggesting that when consciousness of the self appears, it's consciousness of a unified grounding to experience. That unity reflects the unity of the world.

Quoting SEP
In Kant’s conception, by contrast, accounting for our sense of the identity of the conscious subject of different self-attributions requires that this subject be distinct from its representations.


Consciousness of the self requires a division between the subject and object. The self has to have boundaries, in other words.
Paine November 19, 2025 at 23:04 #1025837
Reply to frank
The quote you provided from SEP comes from a particular contrast between Kant and Hume. The argument about what the "I" is in the context of representations is an important issue throughout the book.

The matter of intuition goes to a more "existential" cause of the difference of self and object when Kant says:

Quoting Critique of Pure Reason, B275
The mere, but empirically determined, consciousness of my own
existence proves the existence of objects in space outside me.


frank November 19, 2025 at 23:09 #1025838
Reply to Paine
I continue to have no idea what you're trying to say. I'm sure you're not being purposefully cryptic, but that is the way you're coming across.
Paine November 19, 2025 at 23:50 #1025844
Reply to frank
I am trying to avoid being cryptic by referencing specific portions of the actual text. I was sincere in my general thumbnail that you asked for. But that generality is cryptic as all general descriptions tend to be. That is why I was so reluctant to offer it.

I am doing the best that I can as I understand effort.
frank November 19, 2025 at 23:57 #1025845
Quoting Paine
I am trying to avoid being cryptic by referencing specific portions of the actual text. I was sincere in my general thumbnail that you asked for. But that generality is cryptic as all general descriptions tend to be. That is why I was so reluctant to offer it.

I am doing the best that I can as I understand effort.


We've long had this conflict between us (you and Foolos4) where you dissect passages of text, and I have a much broader outlook. No need to try to resolve it. :grin:
Paine November 19, 2025 at 23:59 #1025846
Reply to frank
Pretty contemptuous last word.

I will leave you with it.
frank November 19, 2025 at 23:59 #1025847
Quoting Paine
Pretty contemptuous last word.

I will leave you with it.


You're projecting.
Paine November 20, 2025 at 00:00 #1025848
Quoting frank
I have a much broader outlook.


frank November 20, 2025 at 00:07 #1025849
Quoting frank
I have a much broader outlook.


I do. To get my bearings, I try to place the text in its historical context. Like, why is Descartes writing this? What is Kant responding to? I'm not saying my way is superior to anybody else's. It's what I do naturally.

You, on the other hand, take a bit of text and use it as the basis for what ends up being self reflection. You want every philosopher to be something like a materialist, and you take one word and draw out a materialist outlook.

Whose approach is more fruitful? Mine is fruitful for me. Yours is fruitful for you. Ultimately, neither is right or wrong.
Paine November 20, 2025 at 00:32 #1025852
Quoting frank
You, on the other hand, take a bit of text and use it as the basis for what ends up being self reflection. You want every philosopher to be something like a materialist, and you take one word and draw out a materialist outlook.


That is not the case. I have argued extensively against Gerson's interpretation of materialism as a general idea in Plato and subsequent literature. Are you remembering my objections to Cornford's view of the forms as an argument for materialism? Nothing could be further from the case. I see that I have only been a cypher in your mind.

I don't want Kant to say this or that. Or if I do, it needs to be a way to read what was written. I don't see the world the way he does in many ways. But he deserves to be fairly represented.

frank November 20, 2025 at 00:34 #1025853
Quoting Paine
But he deserves to be fairly represented.


Cool. How do you interpret the passage you originally posted? I'm curious.
Paine November 20, 2025 at 00:38 #1025855
Reply to frank
I am not going to say more until we deal with your charges about my agenda.
frank November 20, 2025 at 00:46 #1025857
Quoting Paine
I am not going to say more until we deal with your charges about my agenda.


I'm cool with resolving it with a "fair enough." What else?
AmadeusD November 20, 2025 at 00:55 #1025859
Reply to T Clark Interestingly, this is how I've been taught consciousness operates:

Conscious
Preconscious (might become conscious
Subconscious (cannot become conscious).

That would be a neat trick for a God to play on themselves.
Paine November 20, 2025 at 01:04 #1025862
Reply to frank
Then what will be the difference between our points of view?

Will you no longer challenge what I have said in the past as you just did?

I would rather work with that gap than agree to disagree. It is more interesting.


frank November 20, 2025 at 01:10 #1025863
Reply to Paine
Ok. It's just that you posted a passage from Kant in a thread about disproving solipsism. Subsequently, I've been unable to determine how you're reading that passage. Since Kant is known for a persuasive argument that we know about time and space prior to any experience with the world, it seems a little odd to put him forward as disproving solipsism.

Paine November 20, 2025 at 01:17 #1025865
Reply to frank
I can deal with that challenge tomorrow. I will quote from the text I have been referring to and link it to other sections of the other Critiques.
frank November 20, 2025 at 01:22 #1025866
Quoting Paine
I can deal with that challenge tomorrow. I will quote from the text I have been referring to and link it to other sections of the other Critiques.


Ok. I was just asking you to tell me what you think it means.
Paine November 20, 2025 at 01:41 #1025869
Reply to frank
For Kant, in his time, the statement that awareness of self required the existence of "exterior" things was his argument against solipsism.
T_Clark November 20, 2025 at 02:07 #1025873
Quoting AmadeusD
That would be a neat trick for a God to play on themselves.


What kind of god would I be if I couldn’t do something like that?
frank November 20, 2025 at 03:13 #1025883
Quoting Paine
For Kant, in his time, the statement that awareness of self required the existence of "exterior" things was his argument against solipsism.


That's definitely food for thought. Thanks :up:
Ludwig V November 20, 2025 at 13:34 #1025918
Quoting 180 Proof
Searle's tongue was in his cheek: whoever "disproves everybody else's solipsism" presupposes that s/he is not a solipsist.

You are right. That remark is more complicated than it seems. It is true that to seek to disprove everybody else's solipsism is something that only a non-solipsist would want to do. That's why the addition that you can't disprove it to your self is such a surprise.
I can't tell whether he is trying to say that proof or disproof are not relevant to the argument. Everything that others might say can be interpreted in a way compatible with solipsism and vice versa for the non-solipsist. It's not helpful to see solipsism as a thesis or doctrine about the world. It is more like an interpretation (for lack of a better word) of it.

We should start by accepting that the solipsist has a point. That needs to be recognized, and understood. Then it may be possible to show how that point is being misinterpreted, But it is difficult to express the point clearly.
We need to recognize, alongside the recognition of other selves, the unique place in our worlds of our own selves. Put simply, I cannot experience other people's experience or perform other people's actions. There is a sense in which we cannot eat another person's food, or suffer another person's illness or live another person's life. The self - the meaning of "I" - has a uniquely complicated logic. Self-control, self-deception, unselfish action are all difficult issues. I have a unique place in my world, which is curiously close to having no place in it at all. We put too much emphasis on the truth that we are no different from anyone else and too little on the equally true point that we are also unique and not in virtue of the emprical differences (and similarities) between us.

Quoting ProtagoranSocratist
There really is no way of knowing whether or not you are just a product of my imagination..

It depends on what you are paying attention to. As long as you are immersed in your dream, there is no way to understand that it is a dream. It is only after you wake up that you can appreciate a wider context, extract yourself from your immersion, and realize the wider world that shows that it was a dream.

Quoting Paine
For Kant, in his time, the statement that awareness of self required the existence of "exterior" things was his argument against solipsism.


That's one nail that he hits right on the head. I take it as pointing out that one can only grasp one's self by also grasping the not-self all around. The same applies to many (I nearly said "all") concepts. One can only understand what a table is if one understands what is not a table. However, the second half of that process is to understand the distinction between one table and the next. Similarly, awareness of self requires an understanding of what other selves are. (Here comes the specialness of "I" - there is no possibility of my mistaking someone else for myself. What I mean is the understanding that other people are also "I".) The tricky bit is understanding that the differences and similarities are not at all like understanding the difference between one table and the next. Neither table is me.
Mww November 20, 2025 at 14:57 #1025928
Reply to Paine

As you well know, Kant’s refutation concerns itself with the existence of things, but the OP asks about the existence of minds.

It seems that if you’re going to prove the existence of bodies in general from the apodeictic certainty of your own, you still have to prove, given that certainty, the existence of other minds, that is not mere inference.

Even if every human ever, already granted Kant’s argument by and for himself, perhaps without even knowing of its precedence, he still hasn’t proved it for any human not himself.

Quoting Paine
For Kant, in his time, the statement that awareness of self required the existence of "exterior" things was his argument against solipsism.


I’m not so sure the refutation of the established idealism of the day, is the refutation of solipsism itself. The proof for the consciousness of your self cannot follow from my proving the consciousness of my own.

Existence itself is misused with respect to minds anyway. Existence is a category, categories apply only to phenomena, mind is not and cannot be phenomena, so mind is not conditioned by existence. Or, mind in not that which exits, so trying to prove it does or doesn't exist, is unintelligible.

Seems to me, anyway.




180 Proof November 20, 2025 at 18:04 #1025940
ProtagoranSocratist November 20, 2025 at 18:42 #1025942
Quoting Ludwig V
It depends on what you are paying attention to. As long as you are immersed in your dream, there is no way to understand that it is a dream. It is only after you wake up that you can appreciate a wider context, extract yourself from your immersion, and realize the wider world that shows that it was a dream.


like i was saying about Descarte's dream theory in a different discussion, you can "know" that the world is not just a product of your imagination through intuition and experience. You can't prove that your life is nothing but a dream, you can't prove your waking world is the waking world and the dream world is the dream world, you can't prove that you are not the only living person (solipsism), but your intuition will tell you that those theories are all rubbish. Kant's assertion that consistent objects in your environment disprove idealism and extreme solipsism are perhaps evidence, but you can actually dream consistent objects in your environment...even though dream matter tends to be more random and fleeting.
T_Clark November 20, 2025 at 18:57 #1025945
@frank

As I have followed along in this thread, it struck me that solipsism, the simulation argument, and belief in God are equivalent metaphysically.
frank November 20, 2025 at 18:59 #1025946
Quoting T Clark
As I have followed along in this thread, it struck me that solipsism, the simulation argument, and belief in God are equivalent metaphysically.


Metaphysically? or do you mean epistemically?
T_Clark November 20, 2025 at 19:06 #1025948
Quoting frank
Metaphysically? or do you mean epistemically?


Hmm… explain the difference in this case.
frank November 20, 2025 at 19:25 #1025950
Quoting T Clark
Hmm… explain the difference in this case.


Well, if you say belief in God and solipsism are metaphysically equivalent, it sounds like you're saying they contain the same metaphysical outlook.

If you say they're epistemically equivalent, it would sound like you're saying the two are the same with regard to what the holder of the belief actually knows.
T_Clark November 20, 2025 at 21:04 #1025968
Quoting frank
Well, if you say belief in God and solipsism are metaphysically equivalent, it sounds like you're saying they contain the same metaphysical outlook.

If you say they're epistemically equivalent, it would sound like you're saying the two are the same with regard to what the holder of the belief actually knows.


Interesting. Maybe both. I’ll have to think about it more.
Paine November 20, 2025 at 22:53 #1025990
Reply to Mww
I agree that Kant's argument does not directly approach the thesis of solipsism. Kant introduced the goal of his Refutation as:

Quoting C Pure R, Preface B XXXIX
The only thing I can really call a supplement, and that only in the way of proof, is what I have said at B 273 in the form of a new refutation of psychological idealism, and a strict proof (the only possible one, I believe) of the objective reality of outer intuition. No matter how innocent idealism may be held to be as regards the essential ends of metaphysics (though in fact it is not so innocent), it always remains a scandal of philosophy and universal human reason that the existence of things outside us (from which we after all get the whole matter for our cognitions, even for our inner sense) should have to be assumed merely on faith, and that if it occurs to anyone to doubt it, we should be unable to answer him with a satisfactory proof.


It is toward this end Kant figures he has overturned Berkeley and Descartes with one theorem even though they say completely different things:

Quoting ibid. B275
The proof that is demanded must therefore establish that we have experience and not merely imagination of outer things, which cannot be accomplished unless one can prove that even our inner experience, undoubted by Descartes, is possible only under the presupposition of outer experience.


Descartes solved his solipsism problem through a means that Kant rejects. Both Berkeley and Descartes are taking for granted a view of the self that Kant does not.

Now Kant does say a lot of things about the "self" that involves faith. The Critique of Judgement tries to make sense of that.
Ludwig V November 20, 2025 at 23:13 #1025999
Quoting ProtagoranSocratist
you can "know" that the world is not just a product of your imagination through intuition and experience. You can't prove that your life is nothing but a dream, you can't prove your waking world is the waking world and the dream world is the dream world, you can't prove that you are not the only living person (solipsism), but your intuition will tell you that those theories are all rubbish. Kant's assertion that consistent objects in your environment disprove idealism and extreme solipsism are perhaps evidence, but you can actually dream consistent objects in your environment...even though dream matter tends to be more random and fleeting.

A lot depends here on what you call proof and when proof is the appropriate way to go and when alternatives need to be found. I'm not sure I'm happy with intuition - it's a bit like waving a magic wand. I don't say intuition is always wrong, but it's a bit like waving a magic wand. One needs a bit more. The question is what? I'm thinking of looking at things differently. It's a question of attitude and interpretation, rather than proofs and facts.
Ludwig V November 21, 2025 at 07:20 #1026074
Quoting T Clark
As I have followed along in this thread, it struck me that solipsism, the simulation argument, and belief in God are equivalent metaphysically.


Is that because they all assert that the world is very different from what it seems to be. I've always though that the simulation argument and Descartes' demon are equivalent. Does that count?

In that case, quantum physics would go on the list as well.
Mww November 21, 2025 at 14:14 #1026100
Quoting Paine
I agree that Kant's argument does not directly approach the thesis of solipsism…..


Cool. That’s all I was looking for.

Regarding idealism and the refutation thereof, in A, idealism is distinguished as empirical or transcendental. In B, idealism is distinguished as dogmatic or problematic. The introduction of a dedicated title consisting of a “new refutation” in B, meaning over and above the 4th paralogism in A, I think is just his way of uniting the former distinctions into “psychological idealism”, in order to justify his reduction of the idealism being refuted in B, to “material idealism”. In other words, empirical and transcendental idealisms have a common psychological ground, countermanded this way, dogmatic and problematic idealisms have a common material ground, countermanded that way.
————-

What do you think Descartes’ solipsism problem was?
What do you think the view of the self both of them held was, that Kant rejected?

Paine November 21, 2025 at 18:24 #1026118
Quoting Mww
What do you think Descartes’ solipsism problem was?


In Meditations, Descartes wonders if all his experiences in the world are merely dreams and illusion. He asks if the people he sees are machines pretending to be human. He does not have the experience of making everything up, so he wonders if there is an evil demon producing the show. The recognition that a producer is needed divides the solipsism into a least two beings. Descartes opts for a good God over an evil demon which leads to a cosmological proof of said being.

The above is what Kant considers "assuming merely on the basis of faith" in his Preface of the B edition. The cogito ergo sum would seem to undermine this view with the introduction of a rational agency. I read both A and B versions of the paralogisms as a dismantling of the "ergo" part of the sentence. A slice of that pie:

Quoting ibid. B420
From all this one sees that rational psychology has its origin in a mere misunderstanding. The unity of consciousness, which grounds the categories, is here taken for an intuition of the subject as an object, and the category of substance is applied to it. But this unity is only the unity of thinking, through which no object is given; and thus the category of substance, which always presupposes a given intuition, cannot be applied to it, and hence this subject cannot be cognized at all.
(The long footnote at the end of this passage gives a detailed breakdown of his reasoning)

By these criteria, solipsism is an empty statement. The judgement of what exists is a process I am engaged within but did not design. It is here that Berkeley also loses the ground to declare what is imaginary or not. Humans are in the cognition through experience business. We are not allowed into the engineering room. That is why Kant has all of our experience as active agents relate strictly to the theater of Practical Reason.
Mww November 21, 2025 at 20:04 #1026124
Reply to Paine

Interesting. Thanks.

I might go with causal agents rather than active, with respect to practical reason. Unless you have a special meaning for “active”.
Paine November 21, 2025 at 20:40 #1026126
Reply to Mww
Causal agency is the language of practical reason.

I guess I am trying to see a flip side to that where Kant says we have an experience of ourselves through intuition but that does not make us a knowable object. We don't "act" through our thinking alone that would make that possible. Kant often uses a thought experiment imagining an "intellectual intuition" we do not have. Maybe there is a kind of solipsism in that 'missing limb' approach.
Mww November 21, 2025 at 22:04 #1026141
Reply to Paine

If nothing else, we agree the notion of solipsism is empty, thus attempts to disprove it are foolish. At least from the perspective of our mutual reference material.
Paine November 21, 2025 at 22:19 #1026145
Reply to Mww
Yes.

I like the way you carefully qualified the agreement.
frank November 21, 2025 at 22:53 #1026147
Quoting Mww
If nothing else, we agree the notion of solipsism is empty, thus attempts to disprove it are foolish. At least from the perspective of our mutual reference material.


I agree. I think Kant constructs a system which is incompatible with solipsism. That's not the same as disproving it.
Mww November 21, 2025 at 23:07 #1026149
Reply to Paine

Yeah, sorry. I get skittish when language is brought into the dialectic. On the other hand, it might just be that your subtlety escaped me, re: “…language of practical reason”
————-

Quoting frank
I think Kant constructs a system which is incompatible with solipsism


I’m not sure he ever even acknowledged the concept as it is today. Like most -ism’s, it’s a cover for many books.

frank November 21, 2025 at 23:21 #1026151
Reply to Mww
That doesn't even make sense...
Paine November 22, 2025 at 00:01 #1026154
Reply to Mww
Please do not be sorry. Being very specific about agreement and disagreement helps me look for what I am trying to find. I was not speaking ironically.

I figure we do have different views of language. I think there is a benefit in looking for an author's intent before questioning it.
Mww November 22, 2025 at 00:43 #1026160
Reply to Paine

D’accord.