4.06 A proposition can be true or false only in virtue of being a picture
of reality.


4.061 It must not be overlooked that a proposition has a sense that is
independent of the facts: otherwise one can easily suppose that true and
false are relations of equal status between signs and what they signify. In
that case one could say, for example, that 'p' signified in the true way
what 'Pp' signified in the false way, etc.


4.062 Can we not make ourselves understood with false propositions just as
we have done up till now with true ones?--So long as it is known that they
are meant to be false.--No! For a proposition is true if we use it to say
that things stand in a certain way, and they do; and if by 'p' we mean Pp
and things stand as we mean that they do, then, construed in the new way,
'p' is true and not false.


4.0621 But it is important that the signs 'p' and 'Pp' can say the same
thing. For it shows that nothing in reality corresponds to the sign 'P'.
The occurrence of negation in a proposition is not enough to characterize
its sense (PPp = p). The propositions 'p' and 'Pp' have opposite sense, but
there corresponds to them one and the same reality.


4.063 An analogy to illustrate the concept of truth: imagine a black spot
on white paper: you can describe the shape of the spot by saying, for each