In Philosophical Investigations, we find the following statement: “There is one thing of which one can say neither that it is one metre long, nor that it is not one metre long, and that is the standard metre in Paris” (§50). There has been a fair amount of debate about the claim stated by this sentence. Some have argued that it is true, others that it is false. But one thing that has generally been taken for granted – many will say, one thing that is obvious – is that the sentence expresses a claim Wittgenstein believes. He is rejecting the idea that it is possible to say, of the standard metre, that it is a metre long. In what follows I shall try to explain the sort of thing many philosophers have in mind when they discuss that sentence. But I shall also explain why I think they are mistaken. The sentence is certainly in Philosophical Investigations. But like many other sentences in that book, it expresses an idea to which Wittgenstein takes his interlocutor to be committed, rather than Wittgenstein's own view.

To see how Wittgenstein intended his standard-metre statement to be understood, we need to know at least a little bit about the theory he is using the example to criticize. Everyone agrees that the interlocutor he has in mind is some version of his own earlier self: what we might call a Tractarian interlocutor. It will also be useful to have a bit more of Philosophical Investigations §50 before us.