It is a mistake to think of creative activity as something unusual

The symbol and the metaphor are as necessary to science as to poetry.

We are all shot through with enough motives to make a massacre, any day of the week that we want to give them their head.

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.

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

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.

The most powerful drive in the ascent of man is his pleasure in his own skill. He loves to do what he does well. And having done it well, he loves to do it better.