Facing any part of the observable reality, we are never in possession of complete knowledge, nor in a state of complete ignorance, although usually m… - George Pólya

The first rule of style is to have something to say. The second rule of style is to control yourself when, by chance, you have two things to say; say first one, then the other, not both at the same time.

The cookbook gives a detailed description of ingredients and procedures but no proofs for its prescriptions or reasons for its recipes; the proof of the pudding is in the eating. … Mathematics cannot be tested in exactly the same manner as a pudding; if all sorts of reasoning are debarred, a course of calculus may easily become an incoherent inventory of indigestible information.

Nothing is more important than to see the sources of invention which are, in my opinion, more interesting than the inventions themselves.