Everything human is pathetic. The secret source of Humor itself is not joy but sorrow. There is no humor in heaven.
- Following the Equator

The funniest things are the forbidden.
- Notebook, 1879

Humorists of the 'mere' sort cannot survive. Humor is only a fragrance, a decoration.
- Autobiography of Mark Twain, Vol. 2 (2013)

The humorous writer professes to awaken and direct your love, your pity, your kindness--your scorn for untruth, pretension, imposture....He takes upon himself to be the week-day preacher.
- "Notes on Thackeray's Essay on Swift"

Against the assault of laughter, nothing can stand.
- "The Chronicle of Young Satan," Mysterious Stranger Manuscripts

Humor is mankind's greatest blessing.
- Mark Twain, a Biography

Humor must not professedly teach, and it must not professedly preach, but it must do both if it would live forever.
- Mark Twain in Eruption

The humorous story is told gravely; the teller does his best to conceal the fact that he even dimly suspects that there is anything funny about it.
- "How to Tell a Story"

It is not true that owing to my lack of humor I was once discharged from a humorous publication. It's an event that could very likely happen were I on the staff of a humorous paper--but then I'd never get into a fix like that. I'd never undertake to be humorous by contract. If I wanted my worst enemy to be racked I'd make him the editor of a comic paper. For me there must be contrast; for humorous effect I must have solemn background; I'd let my contribution into an undertaker's paper or the London Times. Set a diamond upon a pall of black if you'd have it glisten.
- Interview titled "With Mark Twain," Sydney (Australia) Bulletin, January 4, 1896

Laughter without a tinge of philosophy is but a sneeze of humor. Genuine humor is replete with wisdom.
- quoted in Mark Twain and I, Opie Read (1940)

Humor is the good natured side of a truth.
- quoted in Mark Twain and I, Opie Read (1940)

I have had a "call" to literature, of a low order--i.e. humorous. It is nothing to be proud of, but it is my strongest suit, & if I were to listen to that maxim of stern duty which says that to do right you must multiply the one or the two or the three talents which the Almighty entrusts to your keeping, I would long ago have ceased to meddle with things for which I was by nature unfitted & turned my attention to seriously scribbling to excite the laughter of God's creatures. Poor, pitiful business! Though the Almighty did His part by me- for the talent is a mighty engine when supplied with the steam of education,- which I have not got, & so its pistons & cylinders & shafts move feebly & for a holiday show & are useless for any good purpose...You see in me a talent for humorous writing, & urge me to cultivate it...now, when editors of standard literary papers in the distant east give me high praise, & who do not know me & cannot of course be blinded by the glamour of partiality, that I really begin to believe there must be something in it...I will drop all trifling, & sighing after vain impossibilities, & strive for a fame-unworthy & evanescent though it must of necessity be-if you will record your promise to go hence to the States & preach the gospel when circumstances shall enable you to do so? I am in earnest. Shall it be so?
- Letter to Orion Clemens, October 19 and 20, 1865

So you see, the quality of humor is not a personal or a national monopoly. It's as free as salvation, and, I am afraid, far more widely distributed. But it has its value, I think. The hard and sordid things of life are too hard and too sordid and too cruel for us to know and touch them year after year without some mitigating influence, some kindly veil to draw over them, from time to time, to blur the craggy outlines, and make the thorns less sharp and the cruelties less malignant.
- "A Humorist's Confession," The New York Times, November 26, 1905

I pity the fellow who has to create a dialect or paraphrase the dictionary to get laughs. I can't spell, but I have never stooped to spell cat with a 'k' to get at your funny bone. I love a drink, but I never encouraged drunkenness by harping on its alleged funny side.
- quoted in Abroad with Mark Twain and Eugene Field, Henry W. Fisher (1922)

...humor cannot do credit to itself without a good background of gravity & of earnestness. Humor unsupported rather hurts its author in the estimation of the reader.
- Letter to Michael Simons, January 27 -28, 1873

Probably there is an imperceptible touch of something permanent that one feels instinctively to adhere to true humour, whereas wit may be the mere conversational shooting up of "smartness"--a bright feather, to be blown into space the second after it is launched...Wit seems to be counted a very poor relation to Humour....Humour is never artificial.
- quoted in Sydney Morning Herald, September 17, 1895, pp. 5-6.

The true and lasting genius of humour does not drag you thus to boxes labelled 'pathos,' 'humour,' and show you all the mechanism of the inimitable puppets that are going to perform. How I used to laugh at Simon Tapperwit, and the Wellers, and a host more! But I can't do it now somehow; and time, it seems to me, is the true test of humour. It must be antiseptic.
- quoted in Sydney Morning Herald, September 17, 1895, pp. 5-6.

What is it that strikes a spark of humor from a man? It is the effort to throw off, to fight back the burden of grief that is laid on each one of us. In youth we don't feel it, but as we grow to manhood we find the burden on our shoulders. Humor? It is nature's effort to harmonize conditions. The further the pendulum swings out over woe the further it is bound to swing back over mirth.
- Interview in New York World Sunday Magazine, November 26, 1905

Humor, to be comprehensible to anybody, must be built upon a foundation with which he is familiar. If he can't see the foundation the superstructure is to him merely a freak -- like the Flatiron building without any visible means of support -- something that ought to be arrested.
- "A Humorist's Confession," The New York Times, November 26, 1905

American humor is different entirely to French, German, Scotch, or English humor. And the difference lies in the mode of expression. Though it comes from the English, American humor is distinct. As a rule when an Englishman writes or tells a story, the 'knob' of it, as we would call it, has to be emphasized or italicized, and exclamation points put in. Now, an American story-teller does not do that. He is apparently unconscious of the effect of the joke.
- interview "Mark Twain: Arrival in Auckland," New Zealand Herald, November 21, 1895

I can conceive of many wild and extravagant things when my imagination is in good repair, but I can conceive of nothing quite so wild and extravagant as the idea of my accepting the editorship of a humorous periodical. I should regard that as the saddest (for me) of all occupations. If I should undertake it I should have to add to it the occupation of undertaker, to relieve it in some degree of its cheerlessness. I could edit a serious periodical with relish and a strong interest, but I have never cared enough about humor to qualify me to edit it or sit in judgment upon it.
- Autobiography of Mark Twain, Vol. 2 (2013), p. 197. Dictated 30 August 1906.

English humor is hard to appreciate, though, unless you are trained to it. The English papers, in reporting my speeches, always put 'laughter' in the wrong place.
- quoted in interview ""English Know a Joke, Says Mark Twain" New York Evening World, July 22, 1907, p. 2.