In Begriffsschrift Frege proposed to ignore the part of content that is irrelevant to logic; what remains he called ‘conceptual content’. In ‘On sense and reference’ he renamed this ‘sense’ but failed to stress that it is a notion belonging to the philosophy of logic, not of language. Russell seems to have seen the importance of the notion only briefly. Wittgenstein did not make use of the notion until he was in Norway, and only introduced the terminology of ‘sign’ and ‘symbol’ to mark the distinction while composing the Tractatus. Ramsey proposed to treat sign and symbol as merely two different ways of typing token inscriptions, but this unduly brushes over the difficulties the notion of a symbol involves. The most striking feature of Wittgenstein’s thinking on this is the way that he generalized Frege’s argument for the notion of sense so as to bypass his incorrect particularization to the case of identity.