Certainty ends inquiry.

Science is a tribute to what we can know, although we are fallible.

The preoccupation with the choice of a mate both by male and female I regard as a continuing echo of the major selective force by which we have evolved.

A genius is a man who has two great ideas.

It is very much easier to divide your outlook on the world into two halves, to say that you know this belongs to the daily half and this belongs to the Sunday half.

Astronomy is not the apex of science or of invention. But it is a test of the cast of temperament and mind that underlies a culture.

The discoveries of science, the works of art are explorations - more, are explosions, of a hidden likeness. The discoverer or artist presents in them two aspects of nature and fuses them into one. This is the act of creation, in which an original thought is born, and it is the same act in original science and original art.