Man is a rational animal – so at least I have been told. Throughout a long life, I have looked diligently for evidence in favour of this statement, but so far I have not had the good fortune to come across it, though I have searched in many countries spread over three continents.

In view of the fact that in any future world war nuclear weapons will certainly be employed, and that such weapons threaten the continued existence of mankind, we urge the governments of the world to realize, and to acknowledge publicly, that their purpose cannot be furthered by a world war, and we urge them, consequently, to find peaceful means for the settlement of all matters of dispute between them.

The first man who said "fire burns" was employing scientific method, at any rate if he had allowed himself to be burnt several times. This man had already passed through the two stages of observation and generalization. He had not, however, what scientific technique demands - a careful choice of significant facts on the one hand, and, on the other hand, various means of arriving at laws otherwise than my mere generalization.

Love should be a tree whose roots are deep in the earth, but whose branches extend into heaven.

Work is of two kinds: first, altering the position of matter at or near the earth's surface relative to other matter; second, telling other people to do so.

The essence of the liberal outlook lies not in what opinions are held, but in how they are held; instead of being held dogmatically, they are held tentatively, and with a consciousness that new evidence may at any moment lead to their abandonment.

I can't tell whether I am living in a dream or a nightmare.