Our challenge is to give what account we can of what becomes of life in the solar system, this corner of the universe that is our home; and, most of all, what becomes of men-all men, of all nations, colors, and creeds. This has become one world, a world for all men. It is only such a world that can now offer us life, and the chance to go on.

I tell my students to try early in life to find an unattainable objective.

A scientist lives with all reality. There is nothing better. To know reality is to accept it, and eventually to love it.

Faced with a new mutation in an organism, or a fundamental change in its living conditions, the biologist is frequently in no position whatever to predict its future prospects. He has to wait and see. For instance, the hairy mammoth seems to have been an admirable animal, intelligent and well-accoutered. Now that it is extinct, we try to understand why it failed. I doubt that any biologist thinks he could have predicted that failure. Fitness and survival are by nature estimates of past performance.

I am growing old, and my future, so to speak, is already behind me.

Since we have had a history, men have pursued an ideal of immortality.

Our business is with life, not death.