"A man will be imprisoned in a room with a door that's always ajar, feeling that he might be able to get out, and all he has to do is step outside."

"Is it not a strange phenomenon that in the most highly developed civilizations, people are still afraid of the truth?"

"The great difficulty is to realize that it is not I who am thinking, but the language which is thinking in me."

"Philosophy is not a theory but an activity."

"The true method of philosophy is to say nothing except what can be said, i.e. propositions of natural science."