This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Imagine keeping a diary of a private sensation, say a peculiar recurring feeling, and inventing a sign, S, to mark it down each time it happens, with no definition of S beyond your own private ostensive act of attending to the feeling and associating the sign with it. Wittgenstein's later work argues that this project cannot get off the ground, and the argument matters far beyond the diary case, because it closes off a whole picture of what meaning is. The trouble is not that nobody else could check your diary. It is that you could not check it either. Having decided S means this feeling, whatever counts as correctly applying S again next week depends only on how it seems to you at the time, and whatever seems right to you is right, which is just another way of saying the distinction between using S correctly and merely thinking you have used it correctly has collapsed. A rule that nothing could ever count as breaking is not a rule. Meaning, on this argument, cannot be secured by a private mental ceremony of associating a sign with an inner object, because there is no independent check available to the sign user alone, only to a practice shared with others, correctable by others, answerable to a use that extends beyond any single person's say so. This is why the branch is called philosophy of language rather than philosophy of naming: meaning is not a private label glued to an inner idea, waiting to be spoken. It lives in what a whole community of speakers does with a word, correctably, publicly, together.