We are all afraid for our confidence, for the future, for the world. That is the nature of the human imagination. Yet every man, every civilization, has gone forward because of its engagement with what it has set itself to do.

Beyond all our actions stands the larger shadow: How are we to choose between what we have been taught to think right and something else which manifestly succeeds?

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.

Fifty years from now if an understanding of man's origins, his evolution, his history, his progress is not in the common place of the school books we shall not exist.

The idea that the universe is running down comes from a simple observation about machines. Every machine consumes more energy than it renders.

The paradox of knowledge is not confined to the small, atomic scale; on the contrary, it is as cogent on the scale of man, and even of the stars.

All science is the search for unity in hidden likenesses.