You can buy a man’s time; you can buy a man’s physical presence at a given place; you can even buy a measured number of skilled muscular motions per hour or day. But you cannot buy enthusiasm; you cannot buy initiative; you cannot buy loyalty; you cannot buy the devotion of hearts, minds and souls. You have to earn those things.

Clarence Francis (1888-1985) American business executive, food industry consultant
“The Causes of Industrial Peace,” speech, National Association of Manufacturers (4 Dec 1947)
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Sometimes titled "Philosophy of Management".