ABSTRACT
There is the notion of a language which is private in the sense that it is understood by one person or a group of persons. A private language of this sort presents no philosophical problems, for it is derived from public language; and even if it were not, it will still be translatable into some public language. L. Wittgenstein considered that the notion of a private language rested on two fundamental mistakes: mistake about the nature of experience; and mistake about the nature of language. The sceptic confuses the logical kinds of certainty with the different kinds or degrees of psychological certainty. It is forgotten that mathematical certainty is not a psychological concept. Carnap in his study The Unity of Science gives the name 'protocol language' to any set of sentences which are used to give a 'direct record' of one's own experiences.
