"A philosophical problem has the form: I don't know my way about." — Ludwig Wittgenstein

A nothing will serve just as well as a something about which nothing could be said.

Logic must look after itself. In a certain sense, we cannot make mistakes in logic.

Propositions show what they say: tautologies and contradictions show that they say nothing.

It is one of the chief skills of the philosopher not to occupy himself with questions which do not concern him.