He who acknowledges a kindness has it still, and he who has a grateful sense of it has requited it.

Old age: the crown of life, our play's last act.

The following passage is one of those cited by Copernicus himself in his preface to De Revolutionibus: "The Syracusan Hicetas, as Theophrastus asserts, holds the view that the heaven, sun, moon, stars, and in short all of the things on high are stationary, and that nothing in the world is in motion except the earth, which by revolving and twisting round its axis with extreme velocity produces all the same results as would be produced if the earth were stationary and the heaven in motion. . . ."

If you possess a library and a garden, you have everything you need. (translation from the French) Si vous possedez une bibliotheque et un jardin, vous avez tout ce qu'il vous faut.

In fact the whole passion ordinarily termed love (and heaven help me if I can think of any other term to apply to it) is of such exceeding triviality that I see nothing that I think comparable with it.

Every man's friend is no man's friend.

The enemy is within the gates; it is with our own luxury, our own folly, our own criminality that we have to contend.