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.
4.441 It is clear that a complex of the signs 'F' and 'T' has no object (or
complex of objects) corresponding to it, just as there is none
corresponding to the horizontal and vertical lines or to the brackets.--
There are no 'logical objects'. Of course the same applies to all signs
that express what the schemata of 'T's' and 'F's' express.
4.442 For example, the following is a propositional sign: (Frege's
'judgement stroke' '|-' is logically quite meaningless: in the works of
Frege (and Russell) it simply indicates that these authors hold the
propositions marked with this sign to be true. Thus '|-' is no more a
component part of a proposition than is, for instance, the proposition's
number. It is quite impossible for a proposition to state that it itself is
true.) If the order or the truth-possibilities in a scheme is fixed once
and for all by a combinatory rule, then the last column by itself will be
an expression of the truth-conditions.
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