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["The thing about quotes on the internet is you can not confirm their validity" — Abraham Lincoln]

Miscellaneous quotations that struck my fancy, and that I have found nowhere better to put yet...

For other quotations, see laws, liberty

Quotation, n. The act of repeating erroneously the words of another. The words erroneously repeated.

The Devil's Dictionary, 1911

I have included as much information on specific sources as I can find: all unsourced quotations should best be treated as "attrib" until a proper source comes along (no matter how well-known the quotation: see Burke, Emerson, Voltaire). Please contact me with any known errors/attributions/sources. My thanks to Adam Buchbinder and Edward McGuire for help in sourcing some of these quotations.

Good places to look for sourced quotations:

Key:

sourced quotation
 
translation,
or sourced attribution
unsourced attribution
 

More is different

— title of a paper,
Science, 177:293-296, 1972

That's one small step for [a] man ... one giant leap for mankind

— first words spoken from the moon
20 July1969

Here men from the planet earth first set foot upon the moon, July 1969 A.D. We came in peace for all mankind.

— words read from a plaque left at the landing site
20 July 1969

There is no excellent beauty that hath not some strangeness in the proportion.

— Essays, Civil and Moral, XLIII, Of Beauty, 1625

Vladimir: That passed the time.
Estragon: It would have passed in any case.
Vladimir: Yes, but not so rapidly.

— Waiting for Godot, Act I, 1952

Ever tried. Ever failed. No matter. Try again. Fail again. Fail better.

— Worstward Ho , 1983

We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough to have a chance of being correct. My own feeling is that it is not crazy enough.

— Niels Bohr’s letter to Wolfgang Pauli,
as quoted by Freeman J. Dyson, "Innovation in Physics", Sci. Am. 199(3):74-82, Sept 1958.

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.

Physics and Beyond p102, 1971.

One of the favorite maxims of my father was the distinction between the two sorts of truths, profound truths recognized by the fact that the opposite is also a profound truth, in contrast to trivialities where opposites are obviously absurd.

— Hans Henrik Bohr, "My Father",
in Stefan Rozental (ed), Niels Bohr: His Life and Work as Seen By His Friends and Colleagues, p328, North-Holland, 1967
(originally published in Danish, 1964).

I confess that I have not cleared a path through all seven hundred pages, I confess to having examined only bits and pieces, and yet I know what it is, with that bold and legitimate certainty with which we assert our knowledge of a city, without ever having been rewarded with the intimacy of all the many streets it includes.

— Joyce's Ulysses, in Eliot Weinberger (ed),
Selected Non-Fictions of Jorge Luis Borges pp.12–15, 1999.
Translated from “El Ulises de Joyce” Proa no. 6, Jan 1925.

common misattributions:

When you reach for the stars you may not quite get one, but you won't come up with a handful of mud either.

The perplexity of life arises from there being too many interesting things in it for us to be interested properly in any of them.

— Tremendous Trifles 9, 1909

Many forms of Government have been tried, and will be tried in this world of sin and woe. No one pretends that democracy is perfect or all-wise. Indeed, it has been said that democracy is the worst form of Government except all those others that have been tried from time to time.

— House of Commons speech, 11 November 1947

If you are going through hell, keep going.
The optimist sees opportunity in every danger; the pessimist sees danger in every opportunity.

That willing suspension of disbelief for the moment, which constitutes poetic faith.

— Biographia Literaria, chapter 14, 1817

If you enjoy what you do you'll never work another day in your life.

Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science.

— The Descent of Man, p4, 1871

Any deity worthy of a graven image can cobble up a working universe complete with fake fossils in under a week -- hey, if you're not omnipotent, there's no real point in being a god. But to start with a big ball of elementary particles and end up with the duckbill platypus without constant twiddling requires a degree of subtlety and the ability to Think Things Through: exactly the qualities I'm looking for when I'm shopping for a Supreme Being.

— usenet post, ~1990s (probably rec.arts.sf.written or one of its predecessors)

La perfection est atteinte non quand il ne reste rien à ajouter, mais quand il ne reste rien à enlever.

Perfection [in design] is attained not when there is nothing more to add, but when there is nothing more to take away.

This quotation (or more often, various translations) appears in many places, without a specific reference. However, the original is subtly different:

Il semble que le travail des ingénieurs, des dessinateurs, des calculateurs du bureau d’études ne soit ainsi en apparence, que de polir et d’effacer, d’alléger ce raccord, d’équilibrer cette aile, jusqu’à ce qu’on ne la remarque plus, jusqu’à ce qu’il n’y ait plus une aile accrochée à un fuselage, mais une forme parfaitement épanouie, enfin dégagée de sa gangue, une sorte d’ensemble spontané, mystérieusement lié, et de la même qualité que celle du poème. Il semble que la perfection soit atteinte non quand il n'y a plus rien à ajouter, mais quand il n'y a plus rien à retrancher. Au terme de son évolution, la machine se dissimule.

— Terre des Hommes (chapitre III: L'avion), 1939
available online ici
(translated as Wind, Sand and Stars)

In anything at all, perfection is finally attained not when there is no longer anything to add but when there is no longer anything to take away, when a body has been stripped down to its nakedness.
...
In this spirit do engineers, physicists concerned with thermodynamics, and the swarm of preoccupied draughtsmen tackle their work. In appearance, but only in appearance, they seem to be polishing surfaces and refining away angles, easing this joint or stabilizing that wing, rendering these parts invisible, so that in the end there is no longer a wing hooked to a frame-work but a form flawless in its perfection, completely disengaged from its matrix, a sort of spontaneous whole, its parts mysteriously fused together and resembling in their unity a poem.

— Wind, Sand and Stars (chapter III: The Tool), 1939
(translated by Lewis Galantière)

On the surface it seems that the work of engineers, designers and research mathematicians consists only in polishing and refining, easing this joint and balancing that wing until there is no longer a wing joined visibly to a fuselage, but a perfectly developed form freed at last from its matrix, a spontaneous and mysterious whole with the unified quality of a poem. It seems that perfection is attained not when there is nothing more to add, but when there is nothing more to take away. At the climax of its evolution, the machine conceals itself entirely.

— Wind, Sand and Stars (chapter III: The Aircraft), 1995
(translated by William Rees)

Translation is tricky: should one strive to be literal, or to capture the "intent"? The Galantière translation is rather loose: the original paragraph is split in pieces and distributed around the chapter. The Rees translation is more "literal". Which is better?

A French-as-a-second-language-speaking colleague of mine says that the whole book, despite being published in 1939, has a rather archaic style, and moreover is "very, very French". He also has a comment on the translation of that final retrancher in the original (rather than the enlever of the more widely quoted "simplified" version). Modern French-English dictionaries do say that retrancher means to take away or to cut off, but that may not be the best translation given the overall archaic style. A further colleague, a bilingual English-French software engineer, thinks that in this context it actually means much the same as refactor. So a "better" translation may well be:

perfection [in design] is attained not when there is nothing more to add, but when there is nothing more to refactor.

probable misattribution:

Et nihil prodesset suffragia numerare, ut illam sequeremur opinionem, quae plures habet Auctores: nam si agatur de quaestione difficili, magis credibile est ejus veritatem a paucis inveniri potuisse, quam a multis.

— Regulae Ad Directionem Ingenii, Rule III.2 discussion
written 1628-9, published posthumously

It would be no use totalling up the testimonies in favour of each, meaning to follow that opinion which was supported by the greater number of authors; for if it is a question of difficulty that is in dispute, it is more likely that the truth would have been discovered by few than by many.

— Rules for the Direction of the Mind, Rule III.2 discussion

It would be no good to count heads, and then follow the opinion that has most authorities for it; for if the question that arises is a difficult one, it is more credible that the truth of the matter may have been discovered by few men than by many.

— Rules for the Direction of the Mind, Rule III, para2 discussion
Descartes Philosophical Writings. p. 153-180.
Translated by Elizabeth Anscombe and Peter Thomas Geach. Thomas Nelson and Sons Ltd. 1954.
(as quoted at http://faculty.uccb.ns.ca/philosophy/kbryson/rulesfor.htm)

written later, but published earlier, is the similar:

et que néanmoins la pluralité des voix n'est pas une preuve qui vaille rien, pour les vérités un peu malaisées à découvrir, à cause qu'il est bien plus vraisemblable qu'un homme seul les ait rencontrées que tout un peuple

— Discours de la méthode, seconde partie (1637)
full title: Discours de la méthode pour bien conduire sa raison, et chercher la verité dans les sciences
(as quoted at http://www.gutenberg.org/etext/13846)

I remarked that a plurality of suffrages is no guarantee of truth where it is at all of difficult discovery, as in such cases it is much more likely that it will be found by one than by many.

(as quoted at http://www.gutenberg.org/etext/59)

I could not accept the testimony of the majority, for I thought it worthless as a proof of anything somewhat difficult to discover, since it is much more likely that a single man will have discovered it than a whole people.

(as quoted at http://www.thenagain.info/Classes/Sources/Descartes.html)

— Discourse on Method, part II (1637)
full title: Discourse on the Method of Rightly Conducting the Reason, and Seeking Truth in the Sciences

I think that there is a moral to this story, namely that it is more important to have beauty in one's equations that to have them fit experiment. If Schrödinger had been more confident of his work, he could have published it some months earlier, and he could have published a more accurate equation. It seems that if one is working from the point of view of getting beauty in one's equations, and if one has really a sound insight, one is on a sure line of progress. If there is not complete agreement between the results of one's work and experiment, one should not allow oneself to be too discouraged, because the discrepancy may well be due to minor features that are not properly taken into account and that will get cleared up with further development of the theory.

— "The Evolution of the Physicist' Picture of Nature", Scientific American, 208(5):45-53 May 1963

If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations—then so much the worse for Maxwell's equations. If it is found to be contradicted by observation—well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.

— The Nature of the Physical World (Gifford Lectures, 1927), Macmillan,1928 [p74]

A theory has only the alternative of being right or wrong. A model has a third possibility: it may be right, but irrelevant.

— Jagdish Mehra, ed. The Physicist's Conception of Nature, p618. 1973

Do not go where the path may lead, go instead where there is no path and leave a trail.

— The Spanish Gypsy, book I. 1868 (poem)

this quotation is almost universally attributed to Ralph Waldo Emerson, but it does not appear in any of his writings

A man must consider what a rich realm he abdicates when he becomes a conformist.

— Journal, 22 March 1839

A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines. With consistency a great soul has simply nothing to do. He may as well concern himself with his shadow on the wall. Out upon your guarded lips! Sew them up with packthread, do. Else if you would be a man speak what you think to-day in words as hard as cannon balls, and to-morrow speak what to-morrow thinks in hard words again, though it contradict every thing you said to-day. Ah, then, exclaim the aged ladies, you shall be sure to be misunderstood! Misunderstood! It is a right fool's word. Is it so bad then to be misunderstood? Pythagoras was misunderstood, and Socrates, and Jesus, and Luther, and Copernicus, and Galileo, and Newton, and every pure and wise spirit that ever took flesh. To be great is to be misunderstood.

as quoted in Bartleby, and elsewhere

A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines. With consistency a great soul has simply nothing to do. He may as well concern himself with his shadow on the wall. Speak what you think now in hard words and to-morrow speak what to-morrow thinks in hard words again, though it contradict every thing you said to-day. -- 'Ah, so you shall be misunderstood.'-- Is it so bad then to be misunderstood? Pythagoras was misunderstood, and Socrates, and Jesus, and Luther, and Copernicus, and Galileo, and Newton, and every pure and wise spirit that ever took flesh. To be great is to be misunderstood.

as quoted in Emerson Central, and elsewhere

— Essays: First Series, 'Self-Reliance', para 14, 1841

In skating over thin ice our safety is our speed.

— Essays: First Series, 7. 'Prudence', 1841

The reward of a thing well done is to have done it.

— 'New England Reformers', lecture to the Society, 3 March 1844

Without ambition one starts nothing. Without work one finishes nothing. The prize will not be sent to you. You have to win it. The man who knows how will always have a job. The man who also knows why will always be his boss. As to methods there may be a million and then some, but principles are few. The man who grasps principles can successfully select his own methods. The man who tries methods, ignoring principles, is sure to have trouble.

This quotation is almost universally attributed to Ralph Waldo Emerson on the Web, but with no source given. I have searched through an online source of his writings, and failed to find it.

common misattributions:

To laugh often and much;
to win the respect of intelligent people
     and the affection of children;
to earn the appreciation of honest critics
     and endure the betrayal of false friends;
to appreciate beauty,
to find the best in others;
to leave the world a bit better, whether by a healthy child,
     a garden patch, or a redeemed social condition;
to know even one life has breathed easier because you have lived --
This is to have succeeded.

an "enduring misattribution" to Emerson, with a complicated genesis

"The way we do find out about this proton, the first kind of experiments that we've been making, is to tear the electron off the atom and accelerate the proton faster and faster, and let it plow into a mass of atoms, into a piece of ordinary matter, hoping it'll hit one of the other protons in the, say, hydrogen gas. And then see what happens, what comes out. It would be like trying to find out what a watch is made out of and how the mechanism works by the expedient of smashing two watches together and seeing what kinds of gear wheels fly out."

— The Hunting of the Quark, BBC Horizon, 1974
as excerpted on Lost Horizons: the Big Bang, BBC4, 4 September 2008

It appears that there are enormous differences of opinion as to the probability of a failure with loss of vehicle and of human life. The estimates range from roughly 1 in 100 to 1 in 100,000. The higher figures come from the working engineers, and the very low figures from management.
...
For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.

— Personal observations on the reliability of the Shuttle
Appendix F to the Roger's Commission Report on the Space Shuttle Challenger Accident, 1986

Two roads diverged in a yellow wood,
And sorry I could not travel both
And be one traveler, long I stood
And looked down one as far as I could
To where it bent in the undergrowth;

Then took the other, as just as fair,
And having perhaps the better claim,
Because it was grassy and wanted wear;
Though as for that the passing there
Had worn them really about the same,

And both that morning equally lay
In leaves no step had trodden black.
Oh, I kept the first for another day!
Yet knowing how way leads on to way,
I doubted if I should ever come back.

I shall be telling this with a sigh
Somewhere ages and ages hence:
Two roads diverged in a wood, and I --
I took the one less traveled by,
And that has made all the difference.

— "The Road Not Taken", Mountain Interval, 1916

Life is a verb, not a noun.

— Human Work, p.203, ch.X, 1904

When asked by a group of theologians what one could conclude as to the nature of the Creator from a study of His creation, Haldane is said to have answered, "An inordinate fondness for beetles"

— in G. E. Hutchinson, Am. Nat. 93, 145. 1959

Haldane was once asked if he would risk his life to save a drowning man. "No", replied Haldane, "but I would to save two brothers or eight cousins."

— in Depew & Weber. Darwinism Evolving. 1995.

true greatness is when your name is like ampere, watt, and fourier -- when it's spelled with a lower case letter.
When your vision of what you want to do is what you can do single-handedly, then you should pursue it. The day your vision, what you think needs to be done, is bigger than what you can do single-handedly, then you have to move toward management. And the bigger the vision is, the farther in management you have to go.

— You and Your Research
Bell Communications Research Colloquium Seminar, 7 March 1986
(comments made during the question and answer session)

The past is a foreign country; they do things differently there.

— The Go-Between, 1953
(first line of the novel)

Parturient montes, nascetur ridiculus mus
The mountains will labor and bring forth a ridiculous mouse.
bonus dormitat Homerus
Even Homer nods.

— Ars Poetica

Three minutes' thought would suffice to find this out; but thought is irksome and three minutes is a long time.

— Selected Prose, p. 56. 1905

also as

A moment's thought would have shown him. But a moment is a long time, and thought is a painful process.

Thinking About Thinking, 1975

To think that two and two are four
And neither five nor three
The heart of man has long been sore
And long 'tis like to be.

— Last Poems, no 35, 1922

The mind, in short, works on the data it receives very much as a sculptor works on his block of stone. In a sense the statue stood there from eternity. But there were a thousand different ones beside it, and the sculptor alone is to thank for having extricated this one from the rest. Just so the world of each of us, how so ever different our several views of it may be, all lay embedded in the primordial chaos of sensations, which gave the mere *matter* to the thought of all of us indifferently. We may, if we like, by our reasonings unwind things back to that black and jointless continuity of space and moving clouds of swarming atoms which science calls the only real world. But all the while the world we feel and live in will be that which our ancestors and we, by slowly cumulative strokes of choice, have extricated out of this, like sculptors, by simply removing portions of the given stuff. Other sculptors, other statues from the same stone! Other minds, other worlds from the same monotonous and inexpressive chaos! My world is but one in a million alike embedded, alike real to those who may abstract them. How different must be the worlds in the consciousness of ant, cuttlefish, or crab!

— Principles, vol. I, ch. IX, p. 288

The moral equivalent of war

— Title of a speech, Stanford University, 1906

Old Dr. Jowett, of Oxford, said: "Never apologize, never explain. Get it over with and let them howl," which was good advice.

— Edwin Milton Royle. Peace and Quiet: A Novel, 1916 [p217]

5304: Never explain; never apologise; never repeat the mistake.

— Dictionary of Quotations, 3rd edition, Wordsworth Reference Series, 1998, p194

He [Waugh] exemplifies, like so many of his characters, the great precept of Benjamin Jowett to young Englishmen just starting their careers: "Never apologize, never explain."

— Edmund Wilson. "Never Apologize, Never Explain: The Art of Evelyn Waugh", p143
Classics and Commercials -- A Literary Chronicle of the Forties, 1950

‘Beauty is truth, truth beauty,—that is all
Ye know on earth, and all ye need to know.’

— Ode on a Grecian Urn

Some believers accuse skeptics of having nothing left but a dull, cold, scientific world. I am left with only art, music, literature, theatre, the magnificence of nature, mathematics, the human spirit, sex, the cosmos, friendship, history, science, imagination, dreams, oceans, mountains, love and the wonder of birth. That'll do for me.

— The Skeptic's Guide to the Paranormal, p.viii, 2005

I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to Earth. No single space project in this period will be more impressive to mankind, or more important in the long-range exploration of space; and none will be so difficult or expensive to accomplish.

— Announcement to US Congress, 25 May 1961

We choose to go to the Moon in this decade and do the other things, not because they are easy -- but because they are hard!

— Rice University speech, 12 September 1962

There are nine and sixty ways of constructing tribal lays,
And – every – single – one – of – them – is – right!

— In the Neolithic Age, 1893

The principal applications of any sufficiently new and innovative technology always have been—and will continue to be—applications created by that technology.

— Nobel Lecture, 8 December 2000, Stockholm

EDWIN LAND, the brilliant businessman/scientist who created Polaroid, building it into what is now a $1.6 billion company with a household name, sets high standards for himself. "My motto,' says Land, now 78, "is very personal and may not fit anyone else or any other company. It is: Don't do anything that someone else can do. Don't undertake a project unless it is manifestly important and nearly impossible.

— Subrata N. Chakravarty, "The Vindication of Edward Land"
Forbes, p.83, 4 May 1987

Someone is going to make your product obsolete. Make sure it's you.

— [unverified, probably paraphrased]

The following anecdote is well known in Paris, but has never been printed entire. Laplace once went in form to present some edition of his "Système du Monde" to the First Consul, or Emperor. Napoleon, whom some wags had told that this book contained no mention of the name of God, and who was fond of putting embarrassing questions, received it with—"M. Laplace, they tell me you have written this large book on the system of the universe, and have never even mentioned its Creator." Laplace, who, though the most supple of politicians, was as stiff as a martyr on every point of his philosophy or religion (e. g., even under Charles X he never concealed his dislike of the priests), drew himself up and answered bluntly, "Je n'avais pas besoin de cette hypothèse-là."2 Napoleon, greatly amused, told this reply to Lagrange, who exclaimed, "Ah! c'est une belle hypothèse; ça explique beaucoup de choses."3

2 "I have no need for this hypothesis."
3"Ah, it is a beautiful hypothesis; it explains many things."

— Augustus De Morgan, Budget of Paradoxes, vol 2, p1, 1872.
(from the 2nd edition, 1915)

Lord Ronald said nothing; he flung himself from the room, flung himself upon his horse and rode madly off in all directions.

— Nonsense Novels, "Gertrude the Governess", 1911

a children's story which is enjoyed only by children is a bad children's story.
Critics who treat "adult" as a term of approval, instead of as a merely descriptive term, cannot be adults themselves. To be concerned about being grown up, to admire the grown up because it is grown up, to blush at the suspicion of being childish; these things are the marks of childhood and adolescence. And in childhood and adolescence they are, in moderation, healthy symptoms. Young things ought to want to grow. But to carry on into middle life or even into early manhood this concern about being adult is a mark of really arrested development. When I was ten, I read fairy tales in secret and would have been ashamed if I had been found doing so. Now that I am fifty, I read them openly. When I became a man, I put away childish things, including the fear of childishness and the desire to be very grown up.

— "On Three Ways of Writing for Children", 1952

It was said of Jordan's writings that if he had 4 things on the same footing (as a, b, c, d) they would appear as a, M3', ε2, Π1,2''.

— Littlewood's Miscellany

Science: (n.) The attempt by subroutines in an operating system to deduce the source code, and write the instruction manual.

Had we but world enough, and time,
This coyness, lady, were no crime.
We would sit down and think which way
To walk, and pass our long love's day;
Thou by the Indian Ganges' side
Shouldst rubies find; I by the tide
Of Humber would complain. I would
Love you ten years before the flood,
And you should if you please refuse
Till the conversion of the Jews;
My vegetable love should grow
Vaster than empires and more slow.
An hundred years should go to praise
Thine eyes, and on thy forehead gaze;
Two hundred to adore each breast,
But thirty thousand to the rest;
An age at least to every part,
And the last age should show your heart.
For, lady, you deserve this state,
Nor would I love at lower rate.

But at my back I always hear
Time's wingèd chariot hurrying near,
And yonder all before us lie
Deserts of vast eternity.
Thy beauty shall no more be found,
Nor, in thy marble vaults, shall sound
My echoing song; then worms shall try
That long-preserved virginity,
And your quaint honour turn to dust,
And into ashes all my lust:
The grave's a fine and private place,
But none, I think, do there embrace.

Now therefore, while the youthful hue
Sits on thy skin like morning dew,
And while thy willing soul transpires
At every pore with instant fires,
Now let us sport us while we may;
And now, like am'rous birds of prey,
Rather at once our time devour,
Than languish in his slow-chap't power.
Let us roll all our strength, and all
Our sweetness, up into one ball;
And tear our pleasures with rough strife
Thorough the iron gates of life.
Thus, though we cannot make our sun
Stand still, yet we will make him run.

— To His Coy Mistress

I believe that religion, generally speaking, has been a curse to mankind — that its modest and greatly overestimated services on the ethical side have been more than overborne by the damage it has done to clear and honest thinking.

— Forum, September 1930

Theology — An effort to explain the unknowable by putting it into terms of the not worth knowing

— A Mencken Chrestomathy, 1949

1. We must respect the other fellow's religion, but only in the sense and to the extent that we respect his theory that his wife is beautiful and his children smart.

— Minority Report : H.L. Mencken's Notebooks, 1956

Those who know that they are deep strive for clarity; those who would like to seem deep to the crowd strive for obscurity. For the crowd believes that if it cannot see to the bottom of something it must be deep

— Die fröhliche Wissenschaft (The Gay Science), Book III, 173, 1882

But if you have an enemy, do not requite [pay] him evil with good, for that would put him to shame. Rather prove that he did you some good.

— Thus Spoke Zarathustra, 1885

But a curiosity like mine is after all the most pleasurable of vices — I beg your pardon! I meant to say: the love of truth has its reward in Heaven, and already upon earth.
But a curiosity like mine is once for all the most agreeable of vices — pardon me! I mean to say that the love of truth has its reward in heaven, and already upon earth.
But a curiosity of my type remains after all the most agreeable of all vices — sorry! I meant to say: the love of truth has its reward in heaven and even on earth.
But at all events a curiosity of the sort I have remains the most pleasant of all burdens. Forgive me. I meant to say this: the love of the truth has its reward in heaven and even on earth.

— Beyond Good and Evil, Part III: The Religious Nature, 45, 1885

Wer mit Ungeheuern kämpft, mag zusehn, dass er nicht dabei zum Ungeheuer wird. Und wenn du lange in einen Abgrund blickst, blickt der Abgrund auch in dich hinein.

— Aphorism 146, Jenseits von Gut und Böse, 1886

He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss, the abyss gazes also into you.

— Aphorism 146, Beyond Good and Evil, 1886

"Glaube" heisst Nicht-wissen-wollen, was wahr ist.

— 52, Der Antichrist, 1888

“Faith” means the will to avoid knowing what is true.
"Faith" means not wanting to know what is true.

— section 52, The Antichrist, 1888

What is time? As a physicist I have on occasion answered that question by saying, quite seriously "Time is that great gift of nature which keeps everything from happening at once."

— "What Does a Man Possess?"
The Rotarian, 123(2):47, August 1973

Time is that great gift of nature which keeps everything from happening at once.

— The American Journal of Physics, 46(4):323, 1978
(Here this appears as an isolated "space filler" quotation on the page, with no source cited;
many others cite Henri Bergson as the originator.
It appears in Ray Cummings' The Girl in the Golden Atom, 1922)

As Dharma Kumar paraphrased Joan Robinson, "time is a device to prevent everything happening at once, space is a device to prevent it all happening in Cambridge".

— Angus Maddison, "Confessions of a Chiffrephile",
Banca Nazionale del Lavoro Quarterly Review, 189, June 1994

[Maddison] fondly quotes one of his instructors, Dharma Kumar: "Time is a device to prevent everything happening at once; space is a device to prevent it all happening in Cambridge."

— William J. Bernstein, The Birth of Plenty, chapter 1, McGraw Hill, 2004
referencing
Angus Maddison, Explaining the Economic Performance of Nations, pp438-39,
Edward Elgar Publishing, 1995

While Joan Robinson quoted [Henri] Bergson as saying that "time is a device to stop everything from happening at once", the late Dharma Kumar suggested that "space is a device to stop everything happening in Cambridge"

— Geoffrey Colin Harcourt, 50 Years a Keynesian and Other Essays, Palgrave, 2001

Time is what prevents everything from happening at once.
Space is what prevents everything from happening to me.

John Archibald Wheeler (attrib, in Wikipedia)

It is not enough to joke that "Time is nature's way to keep everything from happening at once. [1]" ...
[1] Graffito from the men's room of the Pecan Street Cafe, Austin, Texas (1976).

John Archibald Wheeler. Time Today.
In J. J. Halliwell, J. Pérez-Mercader, W. H. Zurek (eds.)
Physical Origins of Time Asymmetry, pp.1-30, Chapter 1.
Cambridge University Press, 1996

Je n'ai fait celle-ci plus longue que parce que je n'ai pas eu le loisir de la faire plus courte.

— Lettres provinciales, letter 16, 1657

variously translated, including
I have made this [letter] longer, because I have not had the time to make it shorter.
and
I am sorry for the length of my letter, but I had not the time to write a short one.

this quotation is often attributed to Mark Twain (and less often, to Voltaire, Proust, Pliny the Younger,...)

An important scientific innovation rarely makes its way by gradually winning over and converting its opponents: it rarely happens that Saul becomes Paul. What does happen is that the opponents gradually die out, and that the growing generation is familiarised with the ideas from the beginning.

— Scientific Autobiography, 1949

to carve reality at its joints

— Phaedrus, 265e

various translations have different phrasings:

Socrates: The second principle is that of division into species according to the natural formation, where the joint is, not breaking any part as a bad carver might.

— Jowett Translation

Socrates: That of dividing things again by classes, where the natural joints are, and not trying to break any part, after the manner of a bad carver.

— Fowler translation

'Tis hard to say if greater want of skill
Appear in writing or in judging ill;

'Tis with our judgments as our watches, none
Go just alike, yet each believes his own.

Life, force, and beauty must to all impart,
At once the source, and end, and test of Art.

— excerpts from An Essay on Criticism, Part I, 1711

A little learning is a dangerous thing;
Drink deep, or taste not the Pierian Spring:
There shallow draughts intoxicate the brain,
And drinking largely sobers us again.

Whoever thinks a faultless piece to see,
Thinks what ne'er was, nor is, nor e'er shall be.

Poets, like painters, thus unskill'd to trace
The naked nature and the living grace,
With gold and jewels cover every part,
And hide with ornaments their want of Art.
True Wit is Nature to advantage dress'd,
What oft was thought, but ne'er so well express'd;

In words as fashions the same rule will hold,
Alike fantastic if too new or old:
Be not the first by whom the new are tried,
Nor yet the last to lay the old aside.

Regard not then if wit be old or new,
But blame the False and value still the True.

Fondly we think we honour merit then,
When we but praise ourselves in other men.

Be thou the first true merit to befriend;
His praise is lost who stays till all commend.

Good nature and good sense must ever join;
To err is human, to forgive divine.

— excerpts from An Essay on Criticism, Part II, 1711

Nor be so civil as to prove unjust.
Fear not the anger of the wise to raise;
Those best can bear reproof who merit praise.

'Tis best sometimes your censure to restrain,
And charitably let the dull be vain;
Your silence there is better than your spite,
For who can rail so long as they can write?

For fools rush in where angels fear to tread.

— excerpts from An Essay on Criticism, Part III, 1711

Nature and Nature's laws lay hid in night;
God said "Let Newton be" and all was light.

— proposed epitaph

It did not last: the Devil howling, "Ho!
Let Einstein be!" restored the status quo.

— Sir John Squire (1884–1958)

'The evolution of language ... allows us to dissociate ourselves from our own hypotheses, and to look upon them critically. While an uncritical animal may be eliminated together with its dogmatically held hypotheses, we may formulate our hypotheses, and criticize them. Let our conjectures, our theories, die in our stead!

— Natural Selection and the Emergence of Mind, Dialectica 32(3-4):339-355. 1978

There's a truism that the road to Hell is often paved with good intentions. The corollary is that evil is best known not by its motives but by its methods.

It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat.

— Citizenship in a Republic, speech at the Sorbonne, 23 April 1910

... for a good notation has a subtlety and suggestiveness which make it seem, at times, like a live teacher. Notational irregularities are often the first sign of philosophical errors, and a perfect notation would be a substitute for thought.

— introduction to Wittgenstein's Tractatus Logico-Philosophicus

We all have a tendency to think that the world must conform to our prejudices. The opposite view involves some effort of thought, and most people would die sooner than think – in fact they do so.

— The ABC of Relativity, p.166, 1925

Aristotle maintained that women have fewer teeth than men; although he was twice married, it never occurred to him to verify this statement by examining his wives' mouths.

— The Impact of Science on Society, 1951

All science is either physics or stamp collecting.

— quoted in J. B. Birks, Rutherford at Manchester, 1962

Polonius:
Yet here, Laertes! aboard, aboard, for shame!
The wind sits in the shoulder of your sail,
And you are stay’d for. There, my blessing with thee!
And these few precepts in thy memory
Look thou character. Give thy thoughts no tongue,
Nor any unproportion’d thought his act.
Be thou familiar, but by no means vulgar;
The friends thou hast, and their adoption tried,
Grapple them to thy soul with hoops of steel;
But do not dull thy palm with entertainment
Of each new-hatch’d, unfledg’d comrade. Beware
Of entrance to a quarrel, but, being in,
Bear ’t that th’ opposed may beware of thee.
Give every man thine ear, but few thy voice;
Take each man’s censure, but reserve thy judgment.
Costly thy habit as thy purse can buy,
But not express’d in fancy; rich, not gaudy;
For the apparel oft proclaims the man,
And they in France of the best rank and station
Are most select and generous, chief in that.
Neither a borrower, nor a lender be;
For loan oft loses both itself and friend,
And borrowing dulls the edge of husbandry.
This above all: to thine own self be true,
And it must follow, as the night the day,
Thou canst not then be false to any man.
Farewell; my blessing season this in thee!

— Hamlet, Prince of Denmark. Act I. Scene iii.

Hamlet:
O God, I could be bounded in a nutshell, and count myself a king of infinite space, were it not that I have bad dreams.

— Hamlet, Prince of Denmark. Act II. Scene ii.

Owen Glendower:
I can call spirits from the vasty deep.
Hotspur:
Why, so can I, or so can any man;
But will they come when you do call for them?

— Henry IV, Part I. Act III. Scene i.

he is a barbarian, and thinks that the customs of his tribe and island are the laws of nature.

— Caesar and Cleopatra. 1898

Do not do unto others as you would that they should do unto you. Their tastes may not be the same.

— "Maxims for Revolutionists: The Golden Rule", Man and Superman. 1903

He who can, does. He who cannot, teaches.

— "Maxims for Revolutionists: Education", Man and Superman. 1903

The reasonable man adapts himself to the world: the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

— "Maxims for Revolutionists: Reason", Man and Superman. 1903

Do not try to live for ever. You will not succeed.

— Preface, The Doctor's Dilemma. 1911

The fact that a believer is happier than a skeptic is no more to the point than the fact that a drunken man is happier than a sober one. The happiness of credulity is a cheap and dangerous quality.

— Androcles and the Lion. 1913

Walk! Not bloody likely.

— Eliza Doolittle, Pygmalion, Act 3. 1914

You see things; and you say, 'Why?' But I dream of things that never were; and I say 'Why not?'

— the Serpent, Back to Methusalah, Pt. I, Act I. 1921

We don't stop playing because we grow old, we grow old because we stop playing.
The power of accurate observation is frequently called cynicism by those who don't have it.
Life isn't about finding yourself. Life is about creating yourself.

I met a traveller from an antique land
Who said: Two vast and trunkless legs of stone
Stand in the desert ... Near them, on the sand,
Half sunk, a shattered visage lies, whose frown,
And wrinkled lip, and sneer of cold command,
Tell that its sculptor well those passions read
Which yet survive, stamped on these lifeless things,
The hand that mocked them, and the heart that fed:
And on the pedestal these words appear:
'My name is Ozymandias, king of kings:
Look on my works, ye Mighty, and despair!'
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare
The lone and level sands stretch far away.

— Ozymandius, 1818

On the Internet, nobody knows you're a dog.

— (cartoon caption) The New Yorker, 69(20):61, 5 July 1993

The cruellest lies are often told in silence.

— Virginibus Puerisque, I. 4, "Truth of Intercourse"

To travel hopefully is a better thing than to arrive, and the true success is to labour.

— Virginibus Puerisque, "El Dorado". 1878

George:
Meeting a friend in a corridor, Wittgenstein said: "Tell me, why do people always say it was natural for men to assume that the sun went round the earth, rather than that the earth was rotating?" His friend said, "Well, obviously, because it looks as if the sun is going round the earth." To which the philosopher replied, "Well, what would it have looked like if it had looked as if the earth was rotating?"

— "Jumpers". 1972

So nat'ralists observe, a flea
Hath smaller fleas that on him prey,
And these have smaller fleas that bite 'em,
And so proceed ad infinitum.
Thus ev’ry poet in his kind
Is bit by him that comes behind:
Who, though too little to be seen,
Can teaze, and gall, and give the spleen;

— On Poetry, a Rhapsody (lines 339-346) 1733

Great fleas have little fleas upon their backs to bite 'em,
And little fleas have lesser fleas, and so ad infinitum.
And the great fleas themselves, in turn, have greater fleas to go on,
While these again have greater still, and greater still, and so on.

— Augustus De Morgan, Budget of Paradoxes, vol 2, p191, 1872.
(from the 2nd edition, 1915)

Big whirls have little whirls that feed on their velocity,
and little whirls have lesser whirls and so on to viscosity.

— Lewis Fry Richardson, Weather Prediction by Numerical Process , p66, 1922.

Do not go gentle into that good night,
Old age should burn and rave at close of day;
Rage, rage against the dying of the light.

— 'Do not go gentle into that good night', 1951

The mass of men lead lives of quiet desperation.

Why should we be in such desperate haste to succeed and in such desperate enterprises? If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away.

— Walden; or, Life in the Woods, 1854

Earth is the cradle of humanity, but one cannot live in a cradle forever.

— from a letter, 1911

In the space of one hundred and seventy six years the Lower Mississippi has shortened itself two hundred and forty-two miles. That is an average of a trifle over a mile and a third per year. Therefore, any calm person, who is not blind or idiotic, can see that in the Old Oolitic Silurian Period, just a million years ago next November, the Lower Mississippi was upwards of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing-pole. And by the same token any person can see that seven hundred and forty-two years from now the Lower Mississippi will be only a mile and three-quarters long, and Cairo and New Orleans will have joined their streets together and be plodding comfortably along under a single mayor and a mutual board of aldermen. There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.

— Life on the Mississippi, chapter 17, 1883.

Mr. Clemens was once asked whether he feared death. He said that he did not, in view of the fact that he had been dead for billions and billions of years before he was born, and had not suffered the slightest inconvenience from it.

although this is widely quoted, I have been unable to find a source.
There is a somewhat related quote (found originally on the Twainquotes site, then on Google Books):

While you are asleep you are dead; and whether you stay dead an hour or a billion years the time to you is the same.

— Mark Twain's Notebook, Chapter XXIX, London Days, p323, 1896

Let us endeavor so to live that when we come to die even the undertaker will be sorry.

— Pudd'nhead Wilson, Chapter 6, "Swimming in Glory", 1894
chapter epigraph : Pudd'nhead Wilson's Calendar

Truth is stranger than fiction, but it is because Fiction is obliged to stick to possibilities; Truth isn't.

— Following the Equator, Chapter XV, 1897
chapter epigraph : Pudd'nhead Wilson's New Calendar

Qian li zhi xíng, shi yú zú xià.

— Tao Te Ching, Chapter 64, ~600 BCE

A journey of a thousand li begins with a foot's pace.

— translated by Frederic Henry Balfour, 1884

the journey of a thousand li commenced with a single step.

— translated by James Legge, The Texts of Taoism, OUP, 1891

the ten-day journey began with a single step.

— translated by Aleister Crowley, 1918?
"I was able to divine without hesitation or doubt the precise manner in which Legge had been deceived. He had translated the Chinese with singular fidelity, yet in almost every verse the interpretation was altogether misleading. There was no need to refer to the text from the point of view of scholarship. I had merely to paraphrase his translation in the light of actual knowledge of the true significance of the terms employed."

A journey of three thousand miles begins with one step.

—translated by Dwight Goddard and Henri Borel, 1919
[This is a strange translation, which appears to be both wrong (a li is about a third of a mile, not three miles) and overly literal ("qian li", a thousand li, has the same non-specific meaning as "a thousand miles" in English, that of "a long way"; compare "Sending A Swan Feather from a Thousand Li Away")]

A thousand-mile journey began with a foot put down.

— translated by R. B. Blakney, 1955

The journey of a thousand miles starts from beneath your feet.

— translated by Stephen Mitchell, The Tao Te Ching, A New English Version, Harper Collins, 1988

a journey of a thousand miles begins with a single step.

— translated by Ron Hogan, 2002

Dans ce meilleur des mondes possibles
In this best of all possible worlds
Dans ce pays-ci il est bon de tuer de temps en temps un admiral pour encourager les autres.
In this country we find it good from time to time to shoot an admiral to encourage the others.

— Candide, 1759

Il meglio è l'inimico del bene

— Dictionnaire Philosophique, "Art Dramatique", 1764

Le mieux est l'ennemi du bien.

— La Bégueule, 1772

The best is the enemy of the good.

Il y a eu des gens qui ont dit autrefois: Vous croyez des choses incompréhensibles, contradictoires, impossibles, parce que nous vous l’avons ordonné; faites donc des choses injustes parce que nous vous l’ordonnons. Ces gens-là raisonnaient à merveille. Certainement qui est en droit de vous rendre absurde est en droit de vous rendre injuste. Si vous n’opposez point aux ordres de croire l’impossible l’intelligence que Dieu a mise dans votre esprit, vous ne devez point opposer aux ordres de malfaire la justice que Dieu a mise dans votre coeur. Une faculté de votre âme étant une fois tyrannisée, toutes les autres facultés doivent l’être également. Et c’est là ce qui a produit tous les crimes religieux dont la terre a été inondée.

— Questions sur les miracles, 1765

Formerly there were those who said: You believe things that are incomprehensible, inconsistent, impossible because we have commanded you to believe them; go then and do what is unjust because we command it. Such people show admirable reasoning. Truly, whoever is able to make you absurd is able to make you unjust. If the God-given understanding of your mind does not resist a demand to believe what is impossible, then you will not resist a demand to do wrong to that God-given sense of justice in your heart. As soon as one faculty of your soul has been dominated, other faculties will follow as well. And from this derives all those crimes of religion which have overrun the world.
usually translated as:
Those who can make you believe absurdities can make you commit atrocities

Le doute est un état mental désagréable, mais la certitude est ridicule.
Doubt is an unpleasant mental state, but certainty is a ridiculous one.

common misattributions:

Any one who considers arithmetical methods of producing random digits is, of course, in a state of sin. For, as has been pointed out several times, there is no such thing as a random number – there are only methods to produce random numbers, and a strict arithmetic procedure of course is not such a method.

— "Various Techniques Used in Connection With Random Digits." In Monte Carlo Method , 1951

The introduction of numbers as coordinates ... is an act of violence whose only practical vindication is the special calculatory manageability of the ordinary number continuum with its four basic operations.

— Philosophy of Mathematics and Natural Science, 1949

Characteristic of Weyl was an aesthetic sense which dominated his thinking on all subjects. He once said to me, half joking, ‘My work always tried to unite the true with the beautiful; but when I had to choose one or the other, I usually chose the beautiful’. This remark sums up his personality perfectly. It shows his profound faith in an ultimate harmony of Nature, in which the laws should inevitably express themselves in a mathematically beautiful form. It shows also his recognition of human frailty, and his humor, which always stopped him short of being pompous.

Freeman J. Dyson, Prof. Hemann Weyl, (obituary), Nature, 177:457-8, 1956
as quoted in: Freeman J. Dyson, Birds and Frogs, Notices of the AMS, 56(2)212-223, 2009

By relieving the brain of all unnecessary work, a good notation sets it free to concentrate on more advanced problems, and, in effect, increases the mental power of the race. Before the introduction of the Arabic notation, multiplication was difficult, and the division even of integers called into play the highest mathematical faculties. Probably nothing in the modern world would have more astonished a Greek mathematician than to learn that ... a large proportion of the population of Western Europe could perform the operation of division for the largest numbers. This fact would have seemed to him a sheer impossibility ... Our modern power of easy reckoning with decimal fractions is the almost miraculous result of the gradual discovery of a perfect notation. [...] By the aid of symbolism, we can make transitions in reasoning almost mechanically, by the eye, which otherwise would call into play the higher faculties of the brain. [...] It is a profoundly erroneous truism, repeated by all copy-books and by eminent people when they are making speeches, that we should cultivate the habit of thinking of what we are doing. The precise opposite is the case. Civilisation advances by extending the number of important operations which we can perform without thinking about them. Operations of thought are like cavalry charges in a battle -- they are strictly limited in number, they require fresh horses, and must only be made at decisive moments.

— An Introduction to Mathematics, 1911

It is more important that a proposition be interesting than that it be true.

— Adventures of Ideas, 1933

Do I contradict myself?
Very well then I contradict myself,
(I am large, I contain multitudes.)

— "Song of Myself", part 51, 1855

The Unreasonable Effectiveness of Mathematics in the Natural Sciences

— title of a paper,
Communications in Pure and Applied Mathematics,
vol. 13, No. I, February 1960

see also
R. W. Hamming, "The Unreasonable Effectiveness of Mathematics",
The American Mathematical Monthly, Volume 87, Number 2, February 1980

He once greeted me with the question: "Why do people say that it was natural to think that the sun went round the earth rather than that the earth turned on its axis?" I replied: "I suppose, because it looked as if the sun went round the earth." "Well," he asked, "what would it have looked like if it had looked as if the earth turned on its axis?"

— Elizabeth Anscombe, An Introduction to Wittgenstein's Tractatus, p151, 1959.

Turning and turning in the widening gyre
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold;
Mere anarchy is loosed upon the world.
The blood-dimmed tide is loosed, and everywhere
The ceremony of innocence is drowned;
The best lack all conviction, while the worst
Are full of passionate intensity.

Surely some revelation is at hand;
Surely the Second Coming is at hand.
The Second Coming! Hardly are those words out
When a vast image out of Spiritus Mundi
Troubles my sight; somewhere in the sands of the desert
A shape with a lion body and the head of a man,
A gaze blank and pitiless as the sun,
Is moving its slow thighs, while all about it
Reel shadows of the indignant desert birds.
The darkness drops again; but now I know
That twenty centuries of stony sleep
Were vexed to nightmare by a rocking cradle,
And what rough beast, its hour come round at last,
Slouches towards Bethlehem to be born?

— "The Second Coming", 1921

THE VERY BIG STUPID is a thing which breeds by eating The Future. Have you seen it? It sometimes disguises itself as a good-looking quarterly bottom line, derived by closing the R&D department.

— The Real Frank Zappa Book, Chapter 13, All About Schmucks, 1989

Even in physics, there is no infallible procedure for generating reliable knowledge. The calm order and perfection of well-established theories, accredited by innumerable items of evidence from a thousand different hands, eyes and brains, is not characteristic of the front-line of research, where controversy, conjecture, contradiction and confusion are rife. The physics of undergraduate text-books is 90% true; the contents of the primary research journals of physics is 90% false. The scientific system is as much involved in distilling the former out of the latter as it is in creating and transferring more and more bits of data and items of 'information'.

— Reliable Knowledge: an Exploration of the Grounds for Belief in Science
(setion 2.10, p40) 1978

A bunch of stuff I found in sigs, etc, and have no attribution for. (Some may be original to the indicated sig-owner; I don't know.)

Fiat iustitia, ruat caelum

— Latin legal phrase

Let justice be done though the heavens fall

Amateurs worry about tactics.
Dilettantes worry about strategy.
Professionals worry about logistics.

— ???

If it's supposed to move and it doesn't, spray with WD-40.
If it's not supposed to move and it does, wrap with duct tape.
If it's more complicated than that, use a Swiss Army knife.

— sig, Eloise Beltz-Decker