All of mathematics is a tale about groups.

When the physicists ask us for the solution of a problem, it is not drudgery that they impose on us, on the contrary, it is us who owe them thanks.

In the old days when people invented a new function they had something useful in mind. Now, they invent them deliberately just to invalidate our ancestors' reasoning, and that is all they are ever going to get out of them.

But all of my efforts served only to make me better acquainted with the difficulty, which in itself was something.

It may happen that small differences in the initial conditions produce very great ones in the final phenomena.

It is by logic we prove. It is by intuition we discover.

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