A tautology's truth is certain, a proposition's possible, a contradiction's impossible.

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

The problems are solved, not by giving new information, but by arranging what we have always known.

When we think about the future of the world, we always have in mind its being where it would be if it continued to move as we see it moving now. We do not realize that it moves not in a straight line and that its direction changes constantly.

A propositional sign, applied and thought out, is a thought. A thought is a proposition with a sense.

Language disguises the thought; so that from the external form of the clothes one cannot infer the form of the thought they clothe, because the external form of the clothes is constructed with quite another object than to let the form of the body be recognized.

The world is the totality of facts, not of things