If one looks at the different problems of the integral calculus which arise naturally when one wishes to go deep into the different parts of physics, it is impossible not to be struck by the analogies existing.

What is it indeed that gives us the feeling of elegance in a solution, in a demonstration?

It is with logic that one proves; it is with intuition that one invents.

Geometry is not true, it is advantageous.

The mind uses its faculty for creativity only when experience forces it to do so.

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

The mathematical facts worthy of being studied are those which, by their analogy with other facts, are capable of leading us to the knowledge of a physical law. They reveal the kinship between other facts, long known, but wrongly believed to be strangers to one another.