The scientist does not study nature because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful.

If we ought not to fear mortal truth, still less should we dread scientific truth. In the first place it can not conflict with ethics? But if science is feared, it is above all because it can give no happiness? Man, then, can not be happy through science but today he can much less be happy without it.

It is the harmony of the diverse parts, their symmetry, their happy balance; in a word it is all that introduces order, all that gives unity, that permits us to see clearly and to comprehend at once both the ensemble and the details.

Thus, be it understood, to demonstrate a theorem, it is neither necessary nor even advantageous to know what it means.

Most striking at first is the appearance of sudden illumination, a manifest sign of long unconscious prior work.

I then began to study arithmetical questions without any great apparent result, and without suspecting that they could have the least connexion with my previous researches. Disgusted at my want of success, I went away to spend a few days at the seaside, and thought of entirely different things. One day, as I was walking on the cliff, the idea came to me, again with the same characteristics of conciseness, suddenness, and immediate certainty, that arithmetical transformations of indefinite ternary quadratic forms are identical with those of non-Euclidian geometry.

If nature were not beautiful, it would not be worth knowing, and if nature were not worth knowing, life would not be worth living