I am sitting with a philosopher in the garden; he says again and again 'I know that that’s a tree', pointing to a tree that is near us. Someone else arrives and hears this, and I tell him: 'This fellow isn’t insane. We are only doing philosophy.

'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.

It is an hypothesis that the sun will rise tomorrow: and this means that we do not know whether it will rise.

The logic of the world is prior to all truth and falsehood.

Philosophy is a battle against the bewitchment of our intelligence by means of language.

Every sign by itself seems dead. What gives it life?--In use it is alive. Is life breathed into it there?--Or is the use its life?

Is my understanding only blindness to my own lack of understanding? It often seems so to me.