4.411 It immediately strikes one as probable that the introduction of
elementary propositions provides the basis for understanding all other
kinds of proposition. Indeed the understanding of general propositions
palpably depends on the understanding of elementary propositions.


4.42 For n elementary propositions there are ways in which a proposition
can agree and disagree with their truth possibilities.


4.43 We can express agreement with truth-possibilities by correlating the
mark 'T' (true) with them in the schema. The absence of this mark means
disagreement.


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.
(Thus Frege was quite right to use them as a starting point when he
explained the signs of his conceptual notation. But the explanation of the
concept of truth that Frege gives is mistaken: if 'the true' and 'the
false' were really objects, and were the arguments in Pp etc., then Frege's
method of determining the sense of 'Pp' would leave it absolutely
undetermined.)


4.44 The sign that results from correlating the mark 'I" with truth-
possibilities is a propositional sign.