In the Preface of Philosophical Investigations Wittgenstein says that he wanted it published together with the Tractatus because his new thoughts “could be seen in the right light only by contrast with and against the background of my old way of thinking” (PI, p. x). Nowhere is this more relevant than in his later treatment of the problem of other minds: to understand his later thoughts, one must begin by seeing what he found defective in his earlier ones. In the Tractatus Wittgenstein did not discuss the problem of other minds, but we can nevertheless see that that book implicitly proposes a solution to the problem. To see what this solution is, we must begin by understanding the problem itself.

The Problem of Other Minds

The problem is about how, if at all, skepticism regarding the minds of others is to be overcome. That the problem should arise at all is owing to the plausibility of dualism, the idea that a person is comprised of a mind and a body. A dualist is obliged to think that when we speak of the thoughts and feelings of others we are making a leap – inferential or otherwise – from something we perceive (the body) to something we don't perceive (the other person's thoughts or feelings). This leads to the question: What grounds, if any, can be given for this leap?