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

I think I know what is bothering the students. I think that what we are up against is a generation that is by no means sure that it has a future.

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

If the germ plasm wants to swim in the ocean, it makes itself a fish; if the germ plasm wants to fly in the air, it makes itself a bird. If it wants to go to Harvard, it makes itself a man. The strangest thing of all is that the germ plasm that we carry around within us has done all those things. There was a time, hundreds of millions of years ago, when it was making fish. Then ... amphibia ... reptiles ... mammals, and now it's making men.

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.

There's life all over this universe, but the only life in the solar system is on earth, and in the whole universe we are the only men.

We living things are a late outgrowth of the metabolism of our galaxy. The carbon that enters into our composition was cooked in a remote past in a dying star. The waters of ancient seas set the pattern of ions in our blood. The ancient atmospheres moulded our metabolism.