5.44
Truth-functions are not material functions. If e.g. an affirmation can be produced by repeated denial, is the denial—in any sense—contained in the affirmation? Does “~~p” deny ~p, or does it affirm p; or both? The proposition “~~p” does not treat of denial as an object, but the possibility of denial is already prejudged in affirmation. And if there was an object called “~”, then “~~p” would have to say something other than “p”. For the one proposition would then treat of ~, the other would not.