The problem of other minds is the problem of how to justify the almost universal belief that others have minds very like our own. It is one of the hallowed, if nowadays unfashionable, problems in philosophy. Various solutions to the problem are on offer. It is noteworthy that so many are on offer. Even more noteworthy is that none of the solutions on offer can plausibly lay claim to enjoying majority support.
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There are (at least) two problems of other minds. There is the epistemological problem, concerned with how our beliefs about mental states other than our own might be justified. There is also a conceptual problem: how is it possible for us to form a concept of mental states other than our own. It is generally thought that the materials used to fashion the epistemological problem are the very same materials that produce the conceptual problem. The conceptual problem is generally raised in the context of solving the epistemological problem. One view here is that there can only be an epistemological problem if the conceptual problem is solved, but solving the conceptual problem solves the epistemological problem (Malcolm 1962a). That would be just as well since otherwise the epistemological problem would still be with us. More straightforwardly, some have thought that the conceptual problem is the difficult one without, tantalizingly, showing how easy it is to solve the epistemological problem (Nagel 1986, 19–20).