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.

The world can only be grasped by action, not by contemplation.

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.

Revolutions are not made by fate but by men.

The basis for poetry and scientific discovery is the ability to comprehend the unlike in the like and the like in the unlike.

But nature - that is, biological evolution - has not fitted man to any specific environment. On the contrary, ... he has a rather crude survival kit; and yet -this is the paradox of the human condition - one that fits him to all environments. Among the multitude of animals which scamper, fly, burrow and swim around us, man is the only one who is not locked into his environment. His imagination, his reason, his emotional subtlety and toughness, make it possible for him not to accept the environment but to change it.

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.