5.513 One could say: What is common to all symbols that assert p as well as q, is the proposition “p. q”. What is common to all symbols that assert either p or q, is the proposition “p v q”.
And thus one can say: Two propositions are opposed to one another if they have nothing in common with one another, and: Every proposition has only one negative, because there is only one proposition that lies completely outside of it.
It is evident also in Russell’s notation that “q: p v ~p” says the same as “q”; that “p v ~p” says nothing.
OK. One could equally say the same thing the other way around; that there is only one proposition that lies completely outside of each proposition, because it has only one negative. 5.513 itself says nothing.