5.515
It must be recognized in our symbols that what is connected by “∨”, “.”, etc., must be propositions. And this is the case, for the symbols “p” and “q” presuppose “∨”, “~”, etc. If the sign “p” in “p∨q” does not stand for a complex sign, then by itself it cannot have sense; but then also the signs “p∨p”, “p.p”, etc. which have the same sense as “p” have no sense. If, however, “p∨p” has no sense, then also “p∨q” can have no sense.