Progress is the exploration of our own error. Evolution is a consolidation of what have always begun as errors. And errors are of two kinds: errors that turn out to be true and errors that turn out to be false (which are most of them). But they both have the same character of being an imaginative speculation. I say all this because I want very much to talk about the human side of discovery and progress, and it seems to me terribly important to say this in an age in which most non-scientists are feeling a kind of loss of nerve.

Man is not the most majestic of the creatures; long before the mammals even, the dinosaurs were far more splendid. But he has what no other animal possesses: a jigsaw of faculties, which alone, over three thousand million years of life, made him creative. Every animal leaves traces of what he was. Man alone leaves traces of what he created.

Knowledge is not a loose-leaf notebook of facts. Above all, it is a responsibility for the integrity of what we are, primarily of what we are as ethical creatures.

One original thought is worth the sum total of human knowledge, because it advances the sum total of human knowledge by that one original thought.

The progress of science is the discovery at each step of a new order which gives unity to what had seemed unlike.

A man becomes creative, whether he is an artist or scientist, when he finds a new unity in the variety of nature. He does so by finding a likeness between things which were not thought alike before.

Science is a very human form of knowledge. We are always at the brink of the known; we always feel forward for what is to be hoped. Every judgment in science stands on the edge of error and is personal. Science is a tribute to what we can know although we are fallible.