“But in vitriolic conflicts there is neither appropriateness nor proportion, so the arguments of history and justice become lost in vengeance.”

2000-09, Happiness Can’t Be Faked, 2008

Reflections on the Revolution in France (1790)

Letter accepting the Republican nomination to run for President (12 July 1880)
1880s
Variant: Next in importance to freedom and justice is popular education, without which neither freedom nor justice can be permanently maintained.

Postscript of letter to Mandell Creighton (5 April 1887), puplished in Historical Essays and Studies, by John Emerich Edward Dalberg-Acton (1907), edited by John Neville Figgis and Reginald Vere Laurence, Appendix, p. 505 http://oll.libertyfund.org/?option=com_staticxt&staticfile=show.php%3Ftitle=2201&chapter=203934&layout=html&Itemid=27
Context: ADVICE TO PERSONS ABOUT TO WRITE HISTORY — DON’T
In the Moral Sciences Prejudice is Dishonesty.
A Historian has to fight against temptations special to his mode of life, temptations from Country, Class, Church, College, Party, Authority of talents, solicitation of friends.
The most respectable of these influences are the most dangerous.
The historian who neglects to root them out is exactly like a juror who votes according to his personal likes or dislikes.
In judging men and things Ethics go before Dogma, Politics or Nationality. The Ethics of History cannot be denominational.
Judge not according to the orthodox standard of a system religious, philosophical, political, but according as things promote, or fail to promote the delicacy, integrity, and authority of Conscience.
Put conscience above both system and success.
History provides neither compensation for suffering nor penalties for wrong.

"The Unreasonable Effectiveness of Mathematics in the Natural Sciences," Communications in Pure and Applied Mathematics, February 1960, final sentence.

Epilogue (p. 421)
Academy Series - Priscilla "Hutch" Hutchins, Odyssey (2006)

Notes on Religion (October, 1776). Published in The Works of Thomas Jefferson in Twelve Volumes http://oll.libertyfund.org/ToC/0054.php, Federal Edition, Paul Leicester Ford, ed., New York: G. P. Putnam's Sons, 1904, Vol. 2 http://oll.libertyfund.org/Texts/Jefferson0136/Works/0054-02_Bk.pdf, pp. 267
1770s
Context: Locke denies toleration to those who entertain opinions contrary to those moral rules necessary for the preservation of society; as for instance, that faith is not to be kept with those of another persuasion, … that dominion is founded in grace, or who will not own & teach the duty of tolerating all men in matters of religion, or who deny the existence of a god (it was a great thing to go so far—as he himself says of the parliament who framed the act of toleration … He says 'neither Pagan nor Mahomedan nor Jew ought to be excluded from the civil rights of the Commonwealth because of his religion.' Shall we suffer a Pagan to deal with us and not suffer him to pray to his god? Why have Christians been distinguished above all people who have ever lived, for persecutions? Is it because it is the genius of their religion? No, its genius is the reverse. It is the refusing toleration to those of a different opinion which has produced all the bustles and wars on account of religion. It was the misfortune of mankind that during the darker centuries the Christian priests following their ambition and avarice combining with the magistrate to divide the spoils of the people, could establish the notion that schismatics might be ousted of their possessions & destroyed. This notion we have not yet cleared ourselves from.

Letter to James E. Yeatman of St. Louis, Vice-President of the Western Sanitary Commission (21 May 1865). As quoted on p. 358, and footnoted on p. 562, in Sherman: A Soldier's Passion For Order https://en.wikiquote.org/wiki/Special:BookSources/080938762X (2007), John F. Marszalek, Southern Illinois University Press, Chapter 15 ('Fame Tarnished')
Variant text: I confess, without shame, that I am sick and tired of fighting — its glory is all moonshine; even success the most brilliant is over dead and mangled bodies, with the anguish and lamentations of distant families, appealing to me for sons, husbands, and fathers […] it is only those who have never heard a shot, never heard the shriek and groans of the wounded and lacerated […] that cry aloud for more blood, more vengeance, more desolation. […] I declare before God, as a man and a soldier, I will not strike a foe who stands unarmed and submissive before me, but would rather say—‘Go, and sin no more.’
As quoted in Sherman: Merchant of Terror, Advocate of Peace https://en.wikiquote.org/wiki/Special:BookSources/1455611891 (1992), Charles Edmund Vetter, Pelican Publishing, p. 289
See the Discussion Page for more extensive sourcing information.
1860s, 1865, Letter to James E. Yeatman (May 1865)
Context: I confess without shame that I am tired & sick of war. Its glory is all moonshine. Even success, the most brilliant is over dead and mangled bodies […] It is only those who have not heard a shot, nor heard the shrills & groans of the wounded & lacerated (friend or foe) that cry aloud for more blood & more vengeance, more desolation & so help me God as a man & soldier I will not strike a foe who stands unarmed & submissive before me but will say ‘Go sin no more.

Source: The Principles of Political Economy and Taxation (1821) (Third Edition), Chapter I, Section V, On Value, p. 26