Henri Poincaré

Doubt everything or believe everything: these are two equally convenient strategies. With either we dispense with the need for reflection.

Thinking must never submit itself, neither to a dogma, nor to a party, nor to a passion, nor to an interest, nor to a preconceived idea, nor to whatever it may be, if not to facts themselves, because, for it, to submit would be to cease to be.

It is by logic that we prove, but by intuition that we discover. To know how to criticize is good, to know how to create is better.

It is the simple hypotheses of which one must be most wary; because these are the ones that have the most chances of passing unnoticed.

The mathematician is born, not made.

Mathematics is the art of giving the same name to different things.

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.