“Nothing is more certain than that war promotes science and increases comforts. Utopia may mean no more wars, but universal peace and plenty will never reign until at least one more war raises mankind to a plane of such comfort and ease that nobody on either side of a frontier can even imagine the possibility of resorting to arms. Comfort creates wars and comfort may someday end them.”

Epistulae ad Atticum (Letters to Atticus) Book VII, Letter 14, section 3; as translated by E.O. Winstedt in the Loeb Classical Library http://archive.org/stream/letterstoatticus02ciceuoft#page/68/mode/2up

Homage to Catalonia (1938)

"Of Their Choosing" http://andrewsullivan.theatlantic.com/the_daily_dish/2007/09/of-their-choosi.html, The Daily Dish (20 September 2007)

Quoted in Funny Ladies: The Best Humor from America's Funniest Women by Bill Adler p. 36

Citizenship Papers (2003), A Citizen's Response
Context: To imply by the word "terrorism" that this sort of terror is the work exclusively of "terrorists" is misleading. The "legitimate" warfare of technologically advanced nations likewise is premeditated, politically motivated violence perpetrated against innocents. The distinction between the intention to perpetrate violence against innocents, as in "terrorism," and the willingness to do so, as in "war," is not a source of comfort.

A Great Experiment (1941), p. 189
Context: The truth is, I was never a very good Party man. Probably but for the War of 1914, I should have gone on fairly comfortably as a Conservative official. But those four years burnt into me the insufferable conditions of international relations which made war the acknowledged method — indeed, the only fully authorized method — of settling international disputes. Thenceforth, the effort to abolish war seemed to me, and still seems to me, the only political object worth while.

Dedication, p. 5; this refers to the quotation of Friedrich Schiller from which Asimov derived the title of this novel: "Against stupidity the gods themselves contend in vain."
The Gods Themselves (1972)

Source: The Kite Runner