Imagine a person whose memory could not retain what the word 'pain' meant—so that he constantly called different things by that name—but nevertheless used the word in a way fitting in with the usual symptoms and presuppositions of ‘pain’—in short he uses it as we all do. Here I should like to say: a wheel that can be turned though nothing else moves with it, is not part of the mechanism
Ludwig Wittgenstein, Philosophical Investigations
knowledge, nonsense, sense