5.513
We could say: What is common to all symbols, which assert both p and q, is the proposition “p.q”. What is common to all symbols, which asserts either p or q, is the proposition “p∨q”. And similarly we can say: Two propositions are opposed to one another when they have nothing in common with one another; and every proposition has only one negative, because there is only one proposition which lies altogether outside it. Thus in Russell’s notation also it appears evident that “q:p∨~p” says the same thing as “q”; that “p∨~p” says nothing.