(Sektion 135: Philosophische Untersuchungen von Ludwig Wittgenstein).
135. But then do we have a concept of what a proposition is, of what we understand by "proposition"?--Yes, in so far as we also have a concept of what of what we understand by "game". When asked what a proposition is--whether we think another or ourselves should answer--we will give an example and these will also include what one could call an inductive series of propositions; only in this way do we have a concept of a proposition. (Compare the concept of propositions with the concept of the number.)