5.525 It is incorrect to render the proposition “(Ex). fx” in words – as Russell does – as “fx is possible”.
Certainly, possibility or impossibility of a state of things will not be expressed through a proposition, but by the fact that an expression is a tautology, a meaningful [sinnvoller] proposition, or a contradiction.
That precedent, to which one would always like to appeal, must already lie in the symbol itself.
Precedent? Black says the precedent is “the ground for an assertion of possibility, etc.” Russell implies that if something is possible then it is sometimes true. The ground for saying it is true would then be just the kind of fact that one wanted to say was possible.
Anscombe (see p. 80) sees this view of possibility as a consequence of the picture theory, an undesirable one, that is.
For Russell’s view see, e.g., Logic and Knowledge p. 231.