“A war not only arises, but derives its nature, from the political ideas, the moral sentiments, and the international relations obtaining at the moment when it breaks out.”
Source: Precepts and Judgments (1919), p. 211
Context: A war not only arises, but derives its nature, from the political ideas, the moral sentiments, and the international relations obtaining at the moment when it breaks out.
This amounts to saying : try and know why and with the help of what you are going to act; then you will find out how to act.
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Ferdinand Foch 32
French soldier and military theorist 1851–1929Related quotes

“From principles is derived probability, but truth or certainty is obtained only from facts.”
From principles is derived probability, but truth is obtained only from facts. - Jesse Olney (1798 - 1872), The National Preceptor (Goodwin, 1830), Lesson LXXXV: "Select Sentences," rule # 19 (p. 171).
Misattributed

Source: The Islamic Declaration (1970), p. 53.

Source: Vie de Jésus (The Life of Jesus) (1863), Ch. 5.

Attorney-General v. Sillem and others, "The Alexandra " (1864), 12 W. R. 258.
Charles Eisenstein, Oral presentation in Baltimore, MD March 2012

Source: 1930s, A Dynamic Theory of Personality, 1935, p. 41; partly cited in: Kay Deaux, Mark Snyder (2012) The Oxford Handbook of Personality and Social Psychology. p. 74

Peace and the Public Mind (1935)
Context: The force which makes for war does not derive its strength from the interested motives of evil men; it derives its strength from the disinterested motives of good men. Pacifists have sometimes evaded that truth as making too great a concession to Mars, as seeming to imply (which it does not in fact) that in order to abolish war, men must cease to be noble.
Base motives are, of course, among those which make up the forces that produce war. Base motives are among those which get great cathedrals built and hospitals constructed-contractors' profit-seeking, the vested interests of doctors and clergy. But Europe has not been covered by cathedrals because contractors wanted to make money, or priests wanted jobs.

Speech to the American Red Cross "Promise of Humanity" conference http://mccain.senate.gov/index.cfm?fuseaction=Newscenter.ViewPressRelease&Content_id=820 (6 May 1999).
1990s