Mathematical discoveries, small or great are never born of spontaneous generation.
To invent is to discern, to choose.
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.
Sociology is the science with the greatest number of methods and the least results.
Mathematicians do not study objects, but the relations between objects.
It is with logic that one proves; it is with intuition that one invents.