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

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.

We gain our ends only with the laws of nature; we control her only by understanding her laws.

The child is not a prisoner of its inheritance; it holds its inheritance as a new creation which its future actions will unfold.

There are three creative ideas which, each in its turn, have been central to science. They are the idea of order, the idea of causes, and the idea of chance.

When Da Vinci wanted an effect, he willed, he planned the means to make it happen: that was the purpose of his machines. But the machines of Newton ... are means not for doing but for observing. He saw an effect, and he looked for its cause.

A genius is a man who has two great ideas.