4.431 The expression of agreement and disagreement with the truth-possibilities of elementary propositions expresses the truth-conditions of a proposition.
A proposition is the expression of its truth-conditions.
(Frege quite rightly therefore put them first [vorausgeschickt] as an explanation of the signs of his concept-script. Only the explanation of the concept of truth that we get from Frege is false: if “the True” and “the False” were really objects and the arguments in ~p etc. then Frege’s determination of the sense of “~p” would in no way determine it.)
Anscombe (p. 107): “As a criticism of Frege the point can be summarized by saying: ‘If truth-values are the references of propositions, then you do not specify a sense by specifying a truth-value.’” Because, according to Frege, determining or specifying sense is not the same as determining or specifying reference. Proops (p. 41, note 123) has ‘determination’ here too, noting that in Prototractatus 4.4221 “Wittgenstein makes it plain that in the envisaged circumstances Frege’s “determination” would be unworthy of the name.”