“Our civilization, bequeathed to us by fierce adventurers, eaters of meat and hunters, is so full of hurry and combat, so busy about many things which perhaps are of no importance, that it cannot but see something feeble in a civilization which smiles as it refuses to make the battlefield the test of excellence.”

Women, vol. 3, Society in America (1837).

New York Times magazine op-ed piece, May 2, 2004

Source: The Amazing Maurice and His Educated Rodents

Source: 1930s, Adventures of Ideas (1933), p. 360.

Introduction; part of this has sometimes been paraphrased : Our civilization has not yet fully recovered from the shock of its birth — the transition from the tribal or 'closed society', with its submission to magical forces, to the 'open society' which sets free the critical powers of man.
The Open Society and Its Enemies (1945)

Source: How Europe Underdeveloped Africa (1972), p. 53.

Kalki : or The Future of Civilization (1929)
Context: War with its devastated fields and ruined cities, with its millions of dead and more millions of maimed and wounded, its broken-hearted and defiled women and its starved children bereft of their natural protection, its hate and atmosphere of lies and intrigue, is an outrage on all that is human. So long as this devil-dance does not disgust us, we cannot pretend to be civilized. It is no good preventing cruelty to animals and building hospitals for the sick and poor houses for the destitute so long as we willing to mow down masses of men by machine-guns and poison non-combatants, including the aged and the infirm, women and children — and all for what? For the glory of God and the honour of the nation!
It is quite true that we attempt to regulate war, as we cannot suppress it; but the attempt cannot succeed. For war symbolizes the spirit of strife between two opposing national units which is to be settled by force. When we allow the use of force as the only argument to put down opposition, we cannot rightly discriminate between one kind of force and another. We must put down opposition by mobilizing all the forces at our disposal. There is no real difference between a stick and a sword, or gunpowder and poison gas. So long as it is the recognized method of putting down opposition, every nation will endeavour to make its destructive weapons more and more efficient. War is its only law add the highest virtue is to win, and every nation has to tread this terrific and deadly road. To approve of warfare but criticize its methods, it has been well said is like approving of the wolf eating the lamb but criticizing the table-manners. War is war and not a game of sport to be played according to rules.

Source: 1910s, An Introduction to Mathematics (1911), ch. 5. <!-- pp. 41-42 -->
Context: It is a profoundly erroneous truism, repeated by all copy-books and by eminent people when they are making speeches, that we should cultivate the habit of thinking of what we are doing. The precise opposite is the case. Civilization advances by extending the number of important operations which we can perform without thinking about them. Operations of thought are like cavalry charges in a battle — they are strictly limited in number, they require fresh horses, and must only be made at decisive moments.