Yet, the principle of uncertainty is a bad name. In science or outside of it, we are not uncertain. Our knowledge is merely confined within a certain… - Jacob Bronowski

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.

Freedom is valued in a culture that wants to encourage dissent and to stimulate originality and independence. It belongs to a society which is open to change, and which esteems the agent of change, the individual, above its own peace of mind.

Let me close by reminding you of what Newton actually did on the day that he conceived <math>G = k \frac{mm'}{r^2}</math>. ...Newton did not have any subsidies, grants, funds, Secret Service money. But he had the moon. He said, "... I cannot throw a ball round the world, but let me picture the moon as if it were a ball which has been flung around the world... How long will it take to go round the world?" ...He knew the value of gravity at the earth's surface ...but he did not know the value of the earth's gravity for the moon. He said, "Let us suppose that it is given by an inverse square law. Now, how long will it take the moon to go around?" It comes out at twenty-eight days. As Newton said, "They agreed pretty nearly."