||To a first approximation a private language would be a language that only one person can understand, perhaps as a matter of necessity. Many philosophers have thought that there couldn't be such a language, that any meaningful language must be such that, at least in principle, more than one person could understand it. The main source for arguments against the possibility of private languages has been Wittgenstein's Philosophical Investigations, although it remains a matter of controversy precisely what Wittgenstein aimed to show, what his arguments were, and whether those arguments were successful. More recent work has attempted to articulate in more detail than Wittgenstein arguments for and against the possibility of private languages. A further issue concerns what the consequences would be if it were demonstrated that private languages are not possible. Would it, for example, have consequences for the nature of experience, or its effability?