private-language argument

From Key Terms in Philosophy of Mind (Continuum, 2010):

private-language argument, due to Ludwig WITTGENSTEIN, an argument the conclusion of which is that it is impossible for there to be a language that can be understood by only a single individual. Another way to put the conclusion, then, is that if a language may be understood by any individual, then it must be possible as well for it to be understood by many individuals. Wittgenstein’s discussion of the argument involves contemplation of an attempt to devise a language for keeping a diary of one’s own private sensations. A key issue that arises is, in devising a sign, “S,” to stand for some particular SENSATION, whether there can be any basis for knowing or saying that “S” does indeed stand for that sensation as opposed to something else or nothing at all. The keeper of the allegedly private journal will not be in a position to distinguish whether his grasp of a private ostensive definition of “S” is correct instead of merely seeming correct. And where there can be no graspable distinction between seeming correct and being correct, there is no place for a notion of correctness at all (see also NORMATIVE).