Science, in its ultimate ideal, consists of a set of propositions arranged in a hierarchy, the lowest level of the hierarchy being concerned with particular facts, and the highest with some general law, governing everything in the universe. The various levels in the hierarchy have a two-fold logical connection, travelling one up, one down; the upward connection proceeds by induction, the downward by deduction.

Americans and Englishmen, when they become acquainted with the Balkans, feel an astonished contempt when they study the mutual enmities of Bulgarians and Serbs, of Hungarians and Rumanians. It is evident to them that these enmities are absurd and that the belief of each little nation in its own superiority has no objective basis. But most of them are quite unable to see that the national pride of a Great Power is essentially as unjustifiable as that of a little Balkan country.

Any philosophy worth taking seriously would have to be built upon a firm foundation of unyielding despair.

A priori Logical propositions are such as can be known a priori without study of the actual world.

I never held Negroes to be inherently inferior. The statement in Marriage and Morals refers to environmental conditioning. I have had it withdrawn from subsequent editions because it is clearly ambiguous.

Ethics is in origin the art of recommending to others the sacrifices required for cooperation with oneself.

There are two motives for reading a book; one, that you enjoy it; the other, that you can boast about it.