“The modest front of this small floor,
Believe me, reader, can say more
Than many a braver marble can,—
“Here lies a truly honest man!””

ll. 212-221
A Satire Against Mankind (1679)

“To a Father,” letter 5.
Advice to Young Men (1829)

Waldersee in November, 1877, as quoted by Gordon Alexander Craig, "Germany, 1866-1945" (Oxford University Press, 1978) p.133

Source: Earthsea Books, The Other Wind (2001), Chapter 2 “Palaces” (p. 79)

Speech on Religious Intolerance as presented at the Pittsburgh Opera House (14 October 1879).
Context: They say the religion of your fathers is good enough. Why should a father object to your inventing a better plow than he had? They say to me, do you know more than all the theologians dead? Being a perfectly modest man I say I think I do. Now we have come to the conclusion that every man has a right to think. Would God give a bird wings and make it a crime to fly? Would he give me brains and make it a crime to think? Any God that would damn one of his children for the expression of his honest thought wouldn't make a decent thief. When I read a book and don't believe it, I ought to say so. I will do so and take the consequences like a man.

The trial of Charles B. Reynolds for blasphemy (1887)
Context: Gentlemen, you can never make me believe — no statute can ever convince me, that there is any infinite Being in this universe who hates an honest man. It is impossible to satisfy me that there is any God, or can be any God, who holds in abhorrence a soul that has the courage to express his thought. Neither can the whole world convince me that any man should be punished, either in this world or in the next, for being candid with his fellow-men. If you send men to the penitentiary for speaking their thoughts, for endeavoring to enlighten their fellows, then the penitentiary will become a place of honor, and the victim will step from it — not stained, not disgraced, but clad in robes of glory.
Let us take one more step.
What is holy, what is sacred? I reply that human happiness is holy, human rights are holy. The body and soul of man — these are sacred. The liberty of man is of far more importance than any book; the rights of man, more sacred than any religion — than any Scriptures, whether inspired or not.
What we want is the truth, and does any one suppose that all of the truth is confined in one book — that the mysteries of the whole world are explained by one volume?
All that is — all that conveys information to man — all that has been produced by the past — all that now exists — should be considered by an intelligent man. All the known truths of this world — all the philosophy, all the poems, all the pictures, all the statues, all the entrancing music — the prattle of babes, the lullaby of mothers, the words of honest men, the trumpet calls to duty — all these make up the bible of the world — everything that is noble and true and free, you will find in this great book.
If we wish to be true to ourselves, — if we wish to benefit our fellow-men — if we wish to live honorable lives — we will give to every other human being every right that we claim for ourselves.

Variant: You are braver than you believe,
Stronger than you seem,
And smarter than you think(:
Source: Winnie-the-Pooh

It’s not what somebody believes, it’s experimental proof that counts. And those guys don’t have that.
California Monthly, September 1994.

Canto XXV, lines 46–48 (tr. Longfellow).
The Divine Comedy (c. 1308–1321), Inferno