Proof is an idol before which the mathematician tortures himself.

The electron, as it leaves the atom, crystallises out of Schrodinger's mist like a genie emerging from his bottle.

An electron is no more (and no less) hypothetical than a star. Nowadays we count electrons one by one in a Geiger counter, as we count the stars one by one on a photographic plate.

If an army of monkeys were strumming on typewriters, they might write all the books in the British Museum.

It is also a good rule not to put overmuch confidence in the observational results that are put forward until they are confirmed by theory.

A hundred thousand million Stars make one Galaxy; A hundred thousand million Galaxies make one Universe. The figures may not be very trustworthy, but I think they give a correct impression.

Let us suppose that an ichthyologist is exploring the life of the ocean. He casts a net into the water and brings up a fishy assortment. Surveying his catch, he proceeds in the usual manner of a scientist to systematise what it reveals. He arrives at two generalisations: No sea-creature is less than two inches long. (2) All sea-creatures have gills. These are both true of his catch, and he assumes tentatively that they will remain true however often he repeats it.