The principles upon which this nation was founded are those upon which its survival, no less than its prosperity, depend. These are the principles up… - Harry V. Jaffa

The great difficulty in forming legitimate governments is in persuading those forming the governments that those who are to be their fellow citizens are equal to them in the rights, which their common government is to protect. Catholics and Protestants in sixteenth-century Europe looked upon each other as less than human, and slaughtered each other without pity and without compunction. It was impossible for there to be a common citizenship of those who did not look upon each other as possessing the same right of conscience. How one ought to worship God cannot be settled by majority rule. A majority of one faith cannot ask a minority of another faith to submit their differences to a vote. George Washington, in 1793, said that our governments were not formed in the gloomy ages of ignorance and superstition, but at a time when the rights of man were better understood than in any previous age. Washington was right, in that such rights were, in the latter part of the eighteenth century, in America, better understood. But they were not perfectly understood, as the continued existence of chattel slavery attests. A difference concerning the equal rights of persons of color made the continued existence of a common government of all Americans impossible. A great civil war had to be fought, ending the existence of slavery, reuniting the nation and rededicating it to the proposition that all men are created equal.

[I]t is impossible for men who exercise their reason to believe that any one part of the human race has been marked out by God or nature as so superior to any other. No man is by nature, or by manifest declaration of God's will, the possessor or possession, the master or slave, of another. Whoever asserts such a right to such domination or possession is, in Congress's words from that same document, 'rightfully resistible'.

According to Abraham Lincoln, public opinion always has a central idea from which all its minor thoughts radiate. The central idea of the American Founding—and indeed of constitutional government and the rule of law—was the equality of mankind. This thought is central to all of Lincoln's speeches and writings, from 1854 until his election as president in 1860. It is immortalized in the Gettysburg Address.