Proof, one might say, does not merely shew that it is like this, but: how it is like this. It shows how 13+14 yield 27.

To convince someone of the truth, it is not enough to state it, but rather one must find the path from error to truth.

Knowledge is in the end based on acknowledgement.

A picture is a model of reality.

Ethics and aesthetics are one.

One can defend common sense against the attacks of philosophers only by solving their puzzles, i.e., by curing them of the temptation to attack common sense.

Mathematics is a logical method. . . . Mathematical propositions express no thoughts. In life it is never a mathematical proposition which we need, but we use mathematical propositions only in order to infer from propositions which do not belong to mathematics to others which equally do not belong to mathematics.