Solipsism is the idea that one cannot be sure of anyone's existence but only themself. I think that one can assume this idea to be right and then prove that this is wrong. This self-inconsistency proves it to be wrong. Here is my argument: If solipsism is true, then each person is sure of their existence, i. e. they know that they actually exist. Let's assume mind not to be an illusion. So, each person actually exists, and they know it. Therefore, I could prove that if solipsism is true and mind is no illusion, then each person actually exists. Note that proving that each person actually exists is a contradiction to Solipsism. So I could prove by contradiction that Solipsism is not true.

Is this a valid argument?

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    "If solipsism is true, then each person is sure of his existence" But there is only one persone : me. Dec 17, 2019 at 12:48
  • Wow I see what you mean. So the contradiction rises as I actually assumed solipsism to be wrong implicitly by assuming the existence of some people. Dec 17, 2019 at 12:50
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    Shall I delet the question as I found out the fallacy? Dec 17, 2019 at 12:52
  • You can see other people, but you cannot know they have minds. This is the 'other minds' problem. No need to delete. The question and answer may be useful. . ,
    – user20253
    Dec 17, 2019 at 13:30
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    I think this question has probative value. I wouldn't delete it; often the best questions to learn from are the ones that presume erroneously and serve as the lessons we need to learn. Only those who already know the answers ask perfect questions.
    – J D
    Dec 17, 2019 at 14:44

2 Answers 2


Take the first premise of your argument:

  1. If solipsism is true, then each person is sure of their existence

This premise is true, and compatible with solipsism: the "each" in its formulation would pick out the only person in existence---the one making the argument.

This premise results in the conclusion

  • So, each person actually exists

Again, true: the one person that exists actually exists. But solipsism is OK with that.

Your argument only works against solipsism if "each" is taken to range over more than one person. That is, if there is more than one person in the universe of discourse. But, under that reading, premise 1 is false: if solipsism is true not more than one person (i.e. the person) is sure of their own existence.

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    Thank you for the answer. I agree with you and Mauro (in the comments) about it. This is a flawed argument. Dec 18, 2019 at 16:08

Solipsism and scepticism need to be separated. Solipsism is the theory that only I exist; that I am the whole of reality. It is not a matter of one's not being sure of the existence of anything else; it is the view that there is nothing else but me. 'One' is out of place here; there are no others.

So this 'answer' is not a communication to or with another person ? That's right; there is no other to communicate to or with. It is self-reflection.

Some have supposed that solipsism is incoherent. Thus the late Susan Stebbing held that 'the premises for an argument leading to solipsism are invariably derived from knowledge which is inconsistent with solipsism' (L.S. Stebbing, 'Communication and Verification', Proceedings of the Aristotelian Society, Supplementary Volume 13, 1934: 28). Deep considerations against the tenability of solipsism can also be drawn from Kant and the later Wittgenstein.

But this is just for the record. Your question is not about the coherence and logical tenability of solipsism about about its specification. As specified it is unconnected with scepticism; solus ipse, here for once in philosophy etymology helps: I am the sole self and the sole existent. No doubt about it, if I may put it so.

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