 This is what underlies the ‘correctness’ of identities such \(n + m = r\) except that for Wittgenstein no such identity expresses a truth. On his account, the identity sign disappears in a full analysis of language, wherein sameness and distinction are shown by sameness and distinctness of names, no two of which refer, in fully analysed language, to the same object (this view gives grounds for interpreting mathematical utterances in the Tractatus as unsinnig). Wittgenstein himself did not trouble to show that abandonment of an identity sign would not cripple the expressive power of language but others such as Hintikka (1956) and Wehmeier (2004) have done so. What is left in the underlying language, with identity excised, are substitution rules (Tractatus ¶ 6.23).