“Most men are wicked.”

§ 5
From Lives and Opinions of the Eminent Philosophers by Diogenes Laërtius

Source: Water Sleeps (1999), Chapter 5 (p. 25)

Source: Thoughts Selected from the Writings of Horace Mann (1872), p. 215

The Early Journals and Letters of Fanny Burney, vol. 1, p. 48, journal entry, November 17, 1768.
Letters

A Single Eye, All Light, No Darkness; or Light and Darkness One (1650)

Inhumanity of Slavery. Extract from A Lecture on Slavery, at Rochester. December 8, 1850
1850s, My Bondage and My Freedom (1855)

Antisthenes, 4.
The Lives and Opinions of Eminent Philosophers (c. 200 A.D.), Book 6: The Cynics

Rome, or Reason? A Reply to Cardinal Manning. Part I. The North American Review (1888)
Context: "Whosoever will be saved, before all things it is necessary that he hold the Catholic faith." It is not necessary, before all things, that he be good, honest, merciful, charitable and just. Creed is more important than conduct. The most important of all things is, that he hold the Catholic faith. There were thousands of years during which it was not necessary to hold that faith, because that faith did not exist; and yet during that time the virtues were just as important as now, just as important as they ever can be. Millions of the noblest of the human race never heard of this creed. Millions of the bravest and best have heard of it, examined, and rejected it. Millions of the most infamous have believed it, and because of their belief, or notwithstanding their belief, have murdered millions of their fellows. We know that men can be, have been, and are just as wicked with it as without it.

Speech in Parliament on the American Revolutionary War (February 26, 1781), reported in Hansard (Vol. 22), p. 487, Debate on Mr. Fox's Motion for a Committee.