4.064 Every proposition must already have a sense; assertion cannot give it one, because the sense is the very thing asserted. And the same goes for negation, etc.
Can we say that meaning is not something one does to a sentence then? It already has a meaning if we can do any such thing as assert it, deny it, and so on.
Anscombe (pp. 58-59) says that this is an attack on Frege, but a potentially confusing one, since Frege would agree with it. The problem for him is that he thinks that when one makes a judgment, one “advance[s] from a thought to a truth-value” (Anscombe gives the reference as “Sense and Reference” p. 65 in Philosophical Writings of Gottlob Frege.) Wittgenstein, she says, is attacking this idea. Having a sense means being true or false, so there cannot be propositions that have a sense but are neither true nor false. Frege and Strawson, Anscombe says (and she argues that Wittgenstein agrees), are wrong. They make it seem as though it is merely contingent if we construct a sensical proposition and find that it has a truth-value.