Analyse data just so far as to obtain simplicity and no further.

Mathematicians do not deal in objects, but in relations between objects; thus, they are free to replace some objects by others so long as the relations remain unchanged. Content to them is irrelevant: they are interested in form only.

Need we add that mathematicians themselves are not infallible?

All great progress takes place when two sciences come together, and when their resemblance proclaims itself, despite the apparent disparity of their substance.

One geometry cannot be more true than another; it can only be more convenient.

Science is built up with facts, as a house is with stones. But a collection of facts is no more a science than a heap of stones is a house.

One does not ask whether a scientific theory is true, but only whether it is convenient.