“One never knows whether people have principles on principle or whether for their own personal satisfaction.”

Seventh and Last Joint Debate with Steven Douglas, at Alton, Illinois (15 October 1858)
1850s, Lincoln–Douglas debates (1858)
Context: Now, I have upon all occasions declared as strongly as Judge Douglas against the disposition to interfere with the existing institution of slavery. You hear me read it from the same speech from which he takes garbled extracts for the purpose of proving upon me a disposition to interfere with the institution of slavery, and establish a perfect social and political equality between negroes and white people. Allow me while upon this subject briefly to present one other extract from a speech of mine, more than a year ago, at Springfield, in discussing this very same question, soon after Judge Douglas took his ground that negroes were not included in the Declaration of Independence: I think the authors of that notable instrument intended to include all men, but they did not mean to declare all men equal in all respects. They did not mean to say all men were equal in color, size, intellect, moral development, or social capacity. They defined with tolerable distinctness in what they did consider all men created equal — equal in "certain inalienable rights, among which are life, liberty, and the pursuit of happiness." This they said, and this they meant. They did not mean to assert the obvious untruth that all were then actually enjoying that equality, or yet that they were about to confer it immediately upon them. In fact, they had no power to confer such a boon. They meant simply to declare the right, so that the enforcement of it might follow as fast as circumstances should permit. They meant to set up a standard maxim for free society which should be familiar to all, constantly looked to, constantly labored for, and even, though never perfectly attained, constantly approximated, and thereby constantly spreading and deepening its influence, and augmenting the happiness and value of life to all people, of all colors, everywhere... That is the real issue. That is the issue that will continue in this country when these poor tongues of Judge Douglas and myself shall be silent. It is the eternal struggle between these two principles — right and wrong — throughout the world. They are the two principles that have stood face to face from the beginning of time; and will ever continue to struggle. The one is the common right of humanity, and the other the divine right of kings. It is the same principle in whatever shape it develops itself. It is the same spirit that says, "You toil and work and earn bread, and I'll eat it." No matter in what shape it comes, whether from the mouth of a king who seeks to bestride the people of his own nation and live by the fruit of their labor, or from one race of men as an apology for enslaving another race, it is the same tyrannical principle.

2000s, The Real Abraham Lincoln: A Debate (2002), Q&A
Context: It was a terrible war. The idea that the cost of the war is due to Lincoln is simply absurd. It was a terrible war because the country was deeply divided, and the question of the future of the nation, whether or not it would be based upon principles recognized as principles of individual liberty, or whether the idea of one race dominating another race would be accepted as a means for governance. Let me just read one short statement here that might interest you. "Since the Civil War, in which the Southern States were conquered, against all historical logic and sound sense, the American people have been in a condition of political and popular decay.... The beginnings of a great new social order based on the principle of slavery and inequality were destroyed by that war, and with them also the embryo of a future truly great America." That has been the position of defenders of the Confederacy from Alexander Stephens through Thomas DiLorenzo. Do you know the man who said that was Adolf Hitler?

As quoted in The Writings of Thomas Paine, edited by Moncure D. Conway, vol. 3 (1895), p. 252
1790s, Letter to George Washington (1796)

Margaret Thatcher, The Downing Street Years (HarperCollins, 1993), p. 421.
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Out of Control: The New Biology of Machines, Social Systems and the Economic World (1995)

Letter to Dr Richard Brocklesby (c. 1790s), quoted in R. B. McDowell (ed.), The Correspondence of Edmund Burke, Volume IX: May 1796–July 1797 (Cambridge University Press, 1970), p. 446
Undated

Source: Speech on Reform Bill of 1867, Edinburgh, Scotland (29 October 1867); quoted in William Flavelle Monypenny and George Earle Buckle, The Life of Benjamin Disraeli, Earl of Beaconsfield. Volume II. 1860–1881 (London: John Murray, 1929), p. 291.

Internet Encyclopedia of Philosophy