Respectfully Quoted: A Dictionary of Quotations. 1989.
John Emerich Edward Dalberg, Lord Acton (18341902)
Power tends to corrupt and absolute power corrupts absolutely. Great men are almost always bad men, even when they exercise influence and not authority: still more when you superadd the tendency or the certainty of corruption by authority.
LORD ACTON, letter to Mandell Creighton, April 5, 1887.Acton, Essays on Freedom and Power, ed. Gertrude Himmelfarb, pp. 33536 (1972).