“Why is it relatively easy for a few armament makers to persuade 'men to go to war, to give their lives; and quite impossible for the much larger group who would benefit by another form of general destruction to persuade men to destroy their property? It is broadly, of course, because the folly of burning down houses is plain; the folly of the policies which lead to war is not so plain.”

Source: Utopia (1516), Ch. 1 : Discourses of Raphael Hythloday, of the Best State of a Commonwealth

What Does God Want Us to Do About Russia? (1948)

1860s, Fourth of July Address to Congress (1861)
Context: Our popular Government has often been called an experiment. Two points in it our people have already settled — the successful establishing and the successful administering of it. One still remains — its successful maintenance against a formidable internal attempt to overthrow it. It is now for them to demonstrate to the world that those who can fairly carry an election can also suppress a rebellion; that ballots are the rightful and peaceful successors of bullets, and that when ballots have fairly and constitutionally decided there can be no successful appeal back to bullets; that there can be no successful appeal except to ballots themselves at succeeding elections. Such will be a great lesson of peace, teaching men that what they can not take by an election neither can they take it by a war; teaching all the folly of being the beginners of a war.

Post-war years (1945–1955)
Source: As cited in Churchill by Himself (2008), ed. Langworth, PublicAffairs, p. 511, ISBN 1586489577

1840s, Essays: First Series (1841), Art

The Complete Neurotic's Notebook (1981), Women & men

Graduation Exercises at the United States Military Academy at West Point, New York, U.S. (3 June 1947) http://www.eisenhower.archives.gov/all_about_ike/quotes.html
1940s
Context: War is mankind's most tragic and stupid folly; to seek or advise its deliberate provocation is a black crime against all men. Though you follow the trade of the warrior, you do so in the spirit of Washington — not of Genghis Khan. For Americans, only threat to our way of life justifies resort to conflict.

Letter to William Eustis http://books.google.com/books?id=S088AAAAIAAJ&pg=PA319 (22 June 1809), published in Writings of John Quincy, Adams (1914), The Macmillan company.
Variant: All men profess honesty as long as they can. To believe all men honest would be folly. To believe none so is something worse.

Speech in the House of Commons against the Trade Disputes Bill (30 March 1906), as published in The Speeches of Lord Birkenhead (1929), pp. 15-22.
Context: We are asked to permit a hundred men to go round to the house of a man who wishes to exercise the common law right in this country to sell his labour where and when he chooses, and to 'advise' him or 'peacefully persuade' him not to work. If peaceful persuasion is the real object, why are a hundred men required to do it? … Every honest man knows why trade unions insist on the right to a strong numerical picket. It is because they rely for their objects neither on peacefulness nor persuasion. Those whom they picket cannot be peacefully persuaded. They understand with great precision their own objects, and their own interests, and they are not in the least likely to be persuaded by the representatives of trade unions, with different objects and different interests. But, though arguments may never persuade them, numbers may easily intimidate them. And it is just because argument has failed, and intimidation has succeeded, that the Labour Party insists upon its right to picket unlimited in respect of numbers.