"But the great security against a gradual concentration of the several powers in the same department, consists in giving to those who administer each department the necessary constitutional means and personal motives to resist encroachments of the others. The provision for defense must in this, as in all other cases, be made commensurate to the danger of attack. Ambition must be made to counteract ambition. The interest of the man must be connected with the constitutional rights of the place. It may be a reflection on human nature, that such devices should be necessary to control the abuses of government. But what is government itself, but the greatest of all reflections on human nature? If men were angels, no government would be necessary. If angels were to govern men, neither external nor internal controls on government would be necessary. In framing a government which is to be administered by men over men, the great difficulty lies in this: you must first enable the government to control the governed; and in the next place oblige it to control itself. A dependence on the people is, no doubt, the primary control on the government; but experience has taught mankind the necessity of auxiliary precautions...."--James Madison, The Federalist No. 51, Independent Journal, Wednesday, February 6, 1788.
"Power tends to corrupt, and absolute power corrupts absolutely. Great men are almost always bad men."--John Emerich Edward Dalberg Acton, first Baron Acton, letter to Bishop Mandell Creighton in 1887.
"Unlimited power is apt to corrupt the minds of those who possess it."--William Pitt the Elder, Earl of Chatham, speech to the UK House of Lords in 1770.
"It is not only the slave or serf who is ameliorated in becoming free... the master himself did not gain less in every point of view,... for absolute power corrupts the best natures."--Alphonse Marie Louis de Prat de Lamartine. (English translation of Lamartine's essay France and England: a Vision of the Future, 1848.