The modern physicist is a quantum theorist on Monday, Wednesday, and Friday and a student of gravitational relativity theory on Tuesday, Thursday, and Saturday. On Sunday he is praying. . . that someone will find the reconciliation between the two views."

Progress imposes not only new possibilities for the future but new restrictions.

"A single inattention may lose a chess game, whereas a single successful approach to a problem, among many which have been relegated to the wastebasket, will make a mathematician's reputation."

[M]athematics is a field in which one's blunders tend to show very clearly and can be corrected or erased with a stroke of the pencil.

"The more we get out of the world, the less we leave, and in the long run we shall have to pay our debts at a time that may be very inconvenient for our own survival."