The great end of life is not knowledge but action.

The besetting sin of able men is impatience of contradiction and of criticism. Even those who do their best to resist the temptation, yield to it almost unconsciously and become the tools of toadies and flatterers. "Authorities," "disciples," and "schools" are the curse of science and do more to interfere with the work of the scientific spirit than all its enemies.

Man's Place in Nature.

Unity of plan everywhere lies hidden under the mask: of diversity of structure-the complex is everywhere evolved out of the simple.

Material advancement has its share in moral and intellectual progress. Becky Sharp's acute remark that it is not difficult to be virtuous on ten thousand a year has its applications to nations; and it is futile to expect a hungry and squalid population to be anything but violent and gross.

The man of science has learned to believe in justification, not by faith, but by verification.

The chess-board is the world, the pieces are the phenomena of the universe, the rules of the game are what we call the laws of Nature. The player on the other side is hidden from us.