Knowledge is not a loose leaf notebook of facts.

The air in a man's lungs 10,000,000,000, 000,000,000,000 atoms, so that sooner or later every one of us breathes an atom that has been breathed before by anyone you can think of who has ever lived - Michelangelo or George Washington or Moses.

The preoccupation with the choice of a mate both by male and female I regard as a continuing echo of the major selective force by which we have evolved.

All science is the search for unity in hidden likenesses.

The human baby, the human being, is a mosaic of animal and angel.

Science is a very human form of knowledge. We are always at the brink of the known; we always feel forward for what is to be hoped. Every judgment in science stands on the edge of error and is personal. Science is a tribute to what we can know although we are fallible.

The great poem and the deep theorem are new to every reader, and yet are his own experiences, because he himself recreates them.