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.

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.

Every judgment in science stands on the edge of error, and is personal.

The Principle of Tolerance, fixed once for all the realization that all knowledge is limited. It is an irony of history that at the very time when this was being worked out, there should rise, under Hitler in Germany and other tyrants elsewhere, a counter-conception: a principle of monstrous certainty. When the future looks back on the 1930's, it will think of them as a crucial confrontation of culture as I have been expounding it - the ascent of man against the throwback to the despots' belief that they have absolute certainty.

Science has nothing to be ashamed of even in the ruins of Nagasaki. The shame is theirs who appeal to other values than the human imaginative values which science has evolved.

The act of imagination is the opening of the system so that it shows new connections. Every act of act of imagination is the discovery of likenesses between two things which were thought unlike. An example is Newton’s thinking of the likeness between the thrown apple and moon sailing majestically in the sky. Hence, the ‘discovery’ of the laws of gravity.

The private motives of scientists are not the trend of science. The trend of science is made by the needs of society: navigation before the eighteenth century, manufacture thereafter; and in our age I believe the liberation of personality. Whatever the part which scientists like to act, or for that matter which painters like to dress, science shares the aims of our society just as art does.