Everything should be made as simple as possible, but not simpler.

Everything should be made as simple as possible, but not simpler.

Reader's Digest. Oct. 1977.

[During a lecture:] This has been done elegantly by Minkowski; but chalk is cheaper than grey matter, and we will do it as it comes.

[Attributed by Polya.]

J.E. Littlewood, A
Mathematician's
Miscellany, Methuen
and Co. Ltd., 1953.

A theory has only the alternative of being right or wrong. A model has a third possibility: it may be right, but irrelevant.

Jagdish Mehra (ed.) The Physicist's Conception of Nature, 1973.

If you ask mathematicians what they do, you always get the same answer. They think. They think about difficult and unusual problems. They do not think about ordinary problems: they just write down the answers.

Mathematics
Magazine, v. 65 no.
5, December 1992.

When I am violently beset with temptations, or cannot rid myself of evil thoughts, [I resolve] to do some Arithmetic, or Geometry, or some other study, which necessarily engages all my thoughts, and unavoidably keeps them from wandering.

In T. Mallon, *A
Book of One's
Own.* Ticknor &
Fields, New York,
1984, pp. 106-107.

Human life is proverbially uncertain; few things are more certain than the solvency of a life-insurance company.

In J. R. Newman (ed.) The World of Mathematics, New York: Simon and Schuster, 1956.

To the pure geometer the radius of curvature is an incidental characteristic - like the grin of the Cheshire cat. To the physicist it is an indispensable characteristic. It would be going too far to say that to the physicist the cat is merely incidental to the grin. Physics is concerned with interrelatedness such as the interrelatedness of cats and grins. In this case the "cat without a grin" and the "grin without a cat" are equally set aside as purely mathematical phantasies.

The Expanding Universe..

I believe there are 15,747,724,136,275, 002,577,605,653,961, 181,555,468,044,717, 914,527,116,709,366, 231,425,076,185,631, 031,296 protons in the universe and the same number of electrons.

The Philosophy of
Physical Science.
Cambridge, 1939.

It is impossible to trap modern physics into predicting anything with perfect determinism because it deals with probabilities from the outset.

In J. R. Newman (ed.) The World of Mathematics, New York: Simon and Schuster, 1956.

We have found a strange footprint on the shores of the unknown. We have devised profound theories, one after another, to account for its origins. At last, we have succeeded in reconstructing the creature that made the footprint. And lo! It is our own.

Space, Time and Gravitation. 1920.