The intensity of a conviction that a hypothesis is true has no bearing on whether it is true or false. The importance of the strength of our conviction is only to provide a proportionately strong incentive to find out if the hypothesis will stand up to critical evaluation.

— Peter Medawar

Science attempts to find logic and simplicity in nature. Mathematics attempts to establish order and simplicity in human thought.

— Edward Teller

"The demand for immortality is nowadays essentially teleological. We believe ourselves immortal because we believe ourselves fit for immortality. A 'substance' ought to perish we think, if not worthy to survive, and an insubstantial 'stream' to prolong itself where worthy, if the nature of Things is organized in the rational way we trust it is."

--William James, "The Consciousness of Self", The Principles of Psychology

Nullius in verba ~The Royal Society

MY mistress’ eyes are nothing like the sun
Coral is far more red than her lips’ red:
If snow be white, why then her breasts are dun;
If hairs be wires, black wires grow on her head.
I have seen roses damask’d, red and white,
But no such roses see I in her cheeks;
And in some perfumes is there more delight
Than in the breath that from my mistress reeks.
I love to hear her speak, yet well I know
That music hath a far more pleasing sound:
I grant I never saw a goddess go,—
My mistress, when she walks, treads on the ground:
And yet, by heaven, I think my love as rare
As any she belied with false compare.

-Shakespeare, Sonnet 130

(Incidentally, I find it annoying that I can't post properly formatted poetry or song lyrics in comments. I can't use a single carriage return, and am instead forced to choose between putting a blank line in between every line of the quote, or putting everything on one line.)

Edit: Thank you! Now, is there a way to add spaces to the beginning of a line? HTML has a tendency to ignore whitespace; does the code block override that?

"Do you really mean to tell me that back in Berlin you've got a plan for war against France and one for war against France and England and one for war against France and England and Russia and one for-"

"Aber naturlich," [But naturally] Schlieffen broke in. "And we think of also Austria-Hungary and Italy, though they are now our friend. And we remember Holland and Belgium and Denmark and Sweden and Turkey and-"

The general-in-chief of the United States stared at him. "Jesus Christ, you do mean it," Rosecrans said slowly. "What do they do in that General Staff of yours, Colonel, sit around all say studying maps and timetables and lists of regiments and God knows what all else?"

"Yes," Schlieffen answered, surprised yet again that Rosecrans should be surprised at the idea of military planning. "We believe that, if war comes, we should as little to chance leave as we can."

• Harry Turtledove, How Few Remain

"Whoso wishes to grasp God with his intellect becomes an atheist."

--Nikolaus Ludwig von Zinzendorf

(M. Aug. Gottlieb Spangenbergs Apologetische Schluß-Schrift (Leipzig and Görlitz, 1752; http://berlin.wolf.ox.ac.uk/lists/quotations/quotations_by_ib.html )

"People are not base animals, but people, about 90% animal and 10% something new and different. Religion can be looked on as an act of rebellion by the 90% animal against the 10% new and different (most often within the same person)."

• Paul Lutus

A formula is worth a thousand pictures.

—Edsger Dijkstra

[This is not a quote, but a meta discussion.]

I find it curious that the quotes posted here have higher votes on average than the usual discussion comments, and it makes me think that I have a below-average appreciation for quotations. Why do people value them, I wonder?

When I became convinced that the Universe is natural — that all the ghosts and gods are myths, there entered into my brain, into my soul, into every drop of my blood, the sense, the feeling, the joy of freedom. The walls of my prison crumbled and fell, the dungeon was flooded with light, and all the bolts, and bars, and manacles became dust. I was no longer a servant, a serf, or a slave. There was for me no master in all the wide world — not even in infinite space. I was free — free to think, to express my thoughts — free to live to my own ideal — free to live for myself and those I loved — free to use all my faculties, all my senses — free to spread imagination’s wings — free to investigate, to guess and dream and hope — free to judge and determine for myself — free to reject all ignorant and cruel creeds, all the “inspired” books that savages have produced, and all the barbarous legends of the past — free from the popes and priests — free from all the “called” and “set apart” — free from sanctified mistakes and holy lies — free from the fear of eternal pain — free from the winged monsters of the night — free from devils, ghosts, and gods. For the first time I was free. There were no prohibited places in all the realms of thought — no air, no space, where fancy could not spread her painted wings — no chains for my limbs — no lashes for my back — no fires for my flesh — no master’s frown or threat — no following another’s steps — no need to bow, or cringe, or crawl, or utter lying words. I was free. I stood erect and fearlessly, joyously, faced all worlds.

And then my heart was filled with gratitude, with thankfulness, and went out in love to all the heroes, the thinkers who gave for the liberty of hand and brain — for the freedom of labor and thought — to those who fell in the fierce fields of war, to those who died in dungeons bound with chains — to those who proudly mounted scaffold’s stairs — to those whose bones were crushed, whose flesh was scarred and torn — to those by fire consumed — to all the wise, the good, the brave of every land, whose thoughts and deeds have given freedom to the sons of men. And then I vowed to grasp the torch that they had held, and hold it high, that light might conquer darkness still.

— Robert G. Ingersoll

"Although blinding with science can be used in any argument, many will recognize the special domain of this fallacy as the subjects which like to consider themselves as sciences, but are not.

Science deals with things from atoms to stars at a level where individual differences do not matter. The scientist talks of 'all' rolling bodies or whatever, and formulates general laws to test by experiment.

The trouble with human beings is that, unlike rolling bodies, the individual differences do matter. Often, again unlike rolling bodies, they want to do different things.

Although this might prevent us from being scientific about human beings, it does not stop us pretending to be so. What we do here is to add the word 'science' onto the study, giving us 'economic science', 'political science' and 'social science'. Then we dress them in that white coat of scientific language, and hope that no one will notice the difference."

-- Madsen Pirie, "How To Win Every Argument: The Use and Abuse of Logic"

I have met people who exaggerate the differences [between the morality of different cultures], because they have not distinguished between differences of morality and differences of belief about facts. For example, one man said to me, "Three hundred years ago people in England were putting witches to death. Was that what you call the Rule of Human Nature or Right Conduct?" But surely the reason we do not execute witches is that we do not believe there are such things. If we did-if we really thought that there were people going about who had sold themselves to the devil and received supernatural powers from him in return and were using these powers to kill their neighbours or drive them mad or bring bad weather, surely we would all agree that if anyone deserved the death penalty, then these filthy quislings did. There is no difference of moral principle here: the difference is simply about matter of fact. It may be a great advance in knowledge not to believe in witches: there is no moral advance in not executing them when you do not think they are there. You would not call a man humane for ceasing to set mousetraps if he did so because he believed there were no mice in the house.

-C.S. Lewis

And when one goeth through fire for his teaching--what doth that prove? Verily, it is more when one's teaching cometh out of one's own burning!

-Friedrich Nietzsche, The Antichrist

Never underestimate the difficulty of changing false beliefs by facts. —Harvard economist Henry Rosovsky

What gets us into trouble is not what we don't know. It's what we know for sure that just ain't so. —Mark Twain

Anyone who denies the law of non-contradiction should be beaten and burned until he admits that to be beaten is not the same as not to be beaten, and to be burned is not the same as not to be burned. —Avicenna (980–1037 AD)

You are entitled to your own opinion, but you are not entitled to your own facts. —Daniel Moyniham

It does not matter how frequently something succeeds if failure is too costly to bear. —Nicholas Nassim Taleb

(i.e.: don't forget to put, in your utility functions, the damn appropriate weight of those highly-improbable-but-high-negative-impact tragedies!)

You must engage in these internal dialogues all the time, and you must let yourself lose the arguments gracefully. Writing may be a game of solitaire, but it isn’t a game at which you can cheat.

-Theodore Cheney, Getting the Words Right

the human mind is trained by the knowledge imparted to it and the direction given to its ideas. Only what is great can make it great; the little can only make it little.

-Carl von Clausewitz

Since all things related to akrasia and self motivation are relevant here:

"As a final incentive before giving up a difficult task, try to imagine it successfully accomplished by someone you violently dislike." -K. Zenios

The carting of manure had to begin earlier, so that everything would be finished before the early mowing. The far field had to be ploughed continually, so as to keep it fallow. The hay was to be got in, not on half shares with the peasants, but by hired workers.

The steward listened attentively and obviously made an effort to approve of the master's suggestions; but all the same he had that hopeless and glum look, so familiar to Levin and always so irritating to him. This look said: "That's all very well, but it's as God grants."

Nothing so upset Levin as this tone. But it was a tone common to all stewards, as many of them as he had employed. They all had the same attitude toward his proposals, and therefore he now no longer got angry, but became upset and felt himself still more roused to fight this somehow elemental force for which he could find no other name than "as God grants", and which was continually opposed to him.

-- Leo Tolstoy, "Anna Karenina"

When things are hard to understand, people who suspect they're nonsense generally keep quiet.

-- Paul Graham

The public have an insatiable curiosity to know everything. Except what is worth knowing. Journalism, conscious of this, and having tradesman-like habits, supplies their demands. -Oscar Wilde

There are two mistakes one can make along the road to truth…not going all the way, and not starting.

Buddha

It seems thus impossible that any question about the nature or character of particular sensory qualities should ever arise which is not a question about the differences from (or relations to) other sensory qualities; and the extent to which the effects of its occurrence differ from the effects of the occurrence of any other qualities determines the whole of its character.

To ask beyond this for the explanation of some absolute attribute of sensory qualities seems to be to ask for something which by definition cannot manifest itself in any differences in the consequences which will follow because this rather than any other quality has occurred. Such a factor, however, could by definition not be of relevance to any scientific problem. The 'absolute' quality seems to be unexplainable because there is nothing to explain, because absolute, if it has any meaning at all, can only mean that the attribute which is so described has no scientific significance.

--F. A. Hayek, The Sensory Order (never terse)

"I can't see it, so you must be wrong."

my four-year-old

"Thus Aristotle laid it down that a heavy object falls faster than a light one does. The important thing about this idea is not that he was wrong, but that it never occurred to Aristotle to check it." Albert Szent-Györgyi de Nagyrápolt, winner of the Nobel Prize in Physiology or Medicine.

(approximate, my translation)

Blessed are those who believe without seeing. Who wants to be blessed when they could see.

-- Esa Lappi, my high school math teacher when showing us the proof of some theorem.

Ph.D. comics no.1173

The script:

A grad student in humanities has been called before a hearing to justify his existence.

Student: "It's hard to explain monetarily, but how can you put a price tag on the human soul?"

Student: "The humanities help us appreciate beauty and grow as individuals."

Student: "What good are science and technology if we don't ask ourselves the question, what does it mean to be a human being?"

Chair: "So how's the answer coming along?"

Student: "Oh no, we just ask the question, not actually answer it."

"Everything is open to questioning. That does not mean all answers are equally valid."

-- Kelvin Throop

"There is a superstition in avoiding superstition, when men think to do best if they go furthest from the superstition formerly received."

-- Francis Bacon

"A theory which cannot be mortally endangered cannot be alive."

W. A. H. Rushton, quoted in J.R. Platt, "Strong Inference", Science vol.146, n.3642, 1964.

"Experience does not ever err, it is only your judgement that errs in promising itself results which are not caused by your experiments."

Leonardo Da Vinci

"My interest is in the future because I am going to spend the rest of my life there."

Charles F. Kettering

Besides porking (really) hot babes, flipping out, wailing on guitars, and cutting off heads, a ninja has to train. They have to meditate ALL THE TIME. But most importantly, each morning a ninja should think about going a little crazier than the day before. Beyond thinking about going berserk, a ninja must, by definition, actually go berserk.

Robert Hamburger, REAL Ultimate Power, The Official Ninja Book

I won’t teach a man who is not eager to learn, nor will I explain to one incapable of forming his own ideas. Nor have I anything more to say to those who, after I have made clear one corner of the subject, cannot deduce the other three.

Confucius

The unwillingness to tolerate or respect any social forces which are not recognizable as the product of intelligent design, which is so important a cause of the present desire for comprehensive economic planning, is indeed only one aspect of a more general movement. We meet the same tendency in the field of morals and conventions, in the desire to substitute an artificial for the existing languages, and in the whole modern attitude toward processes which govern the growth of knowledge. The belief that only a synthetic system of morals, an artificial language, or even an artificial society can be justified in an age of science, as well as the increasing unwillingness to bow before any moral rules whose utility is not rationally demonstrated, or to conform with conventions whose rationale is not known, are all manifestations of the same basic view which wants all social activity to be recognizably part of a single coherent plan. They are the results of that same rationalistic "individualism" which wants to see in everything the product of conscious individual reason.

Friedrich Hayek, Individualism: True and False

The statement that all of us are purportedly able to coherently conceive or imagine a certain situation - for instance, an imitation man or a zombie - is rather trivial from a philosophical point of view because ultimately it is just an empirical claim about the history of the brain and its functional architecture. It is a statement about a world that is phenomenally possible for human beings. It is not a statement about the modal strength of the relationship between physical and phenomenal properties; logical possibility (or necessity) is not implied by phenomenological possibility (or necessity). From the simple fact that beings like ourselves are able to phenomenally simulate a certain apparently possible world, it does not follow that a consistent or even only an empirically plausible description of this world exists. -- Thomas Metzinger

"Now I'll never know if I was right."

-- final words of Adric, in Dr. Who, "Earthshock", on realizing that he's about to crash into the Earth

The master mathematician sat in his private room and pushed the papers from him. His calculations were already finished. In a small white phial there still remained a little of the drug that had kept him awake and active for four long nights. Each day, serene, explicit, patient as ever, he had given his lecture to his students, and then had come back at once to this momentous calculation. His face was grave, a little drawn and hectic from his drugged activity. For some time he seemed lost in thought. Then he went to the window, and the blind went up with a click. Half way up the sky, over the clustering roofs, chimneys and steeples of the city, hung the star.

He looked at it as one might look into the eyes of a brave enemy. "You may kill me," he said after a silence. "But I can hold you--and all the universe for that matter--in the grip of this little brain. I would not change. Even now."

-- H.G. Wells, "The Star", 1897

A great many years ago, a couple of Jehovah Witnesses bit off more than they could chew with my grandmother. During the unsolicited conversation one of them remarked, "Only God can make a rainbow". To which my grandmother-who was watering her plants at the time-said, "Nonsense!", and created her own rainbow with a spray of water from the hose. Family lore has it that was the end of the conversation.

-- seen on Livejournal

A behavioral policy based on an inside strategy permits the alcoholic to sit at the bar and rehearse the reasons to abstain. An outside strategy identifies a principle or rule of conduct that produces the most accurate or desirable available outcome, and sticks to that rule despite the subjective pull to abandon the principle. A behavioral policy based on an outside strategy recommends that you avoid the bar in the first place.

-- Michael Bishop, 50 Years of Successful Predictive Modeling Should Be Enough: Lessons for Philosophy of Science

"Why then 'tis none to you; for there is nothing either good or bad, but thinking makes it so."

Hamlet Act 2, scene 2, 239–251

Mathematics is rational, not reasonable.

-- Terry Padden, in "Ultimately, in Physics the Rational shall become Reasonable!"

Our minds are like inmates, captive to our biology, unless we manage a cunning escape.

-- Nassim Taleb

People often lack the discipline to adhere to a superior strategy that doesn't "feel" right. Reasoning in a way that sometimes "feels" wrong takes discipline.

-- Michael Bishop, Epistemology and the psychology of human judgement

Dear Meg,

Please don't try to trisect the angle. . . It's not a matter of being clever.

Ian Stewart, Letters to a Young Mathematician

However beautiful the strategy, you should occasionally look at the results.

-- Winston Churchill

You want to learn from experience, but you want to learn from other people’s experience when you can.

Warren Buffett

Perfecting oneself is as much unlearning as it is learning.

-- Edsger Dijkstra

All that glitters is not gold

Unknown Origin

You got to have a dream,

If you don't have a dream,

How you gonna have a dream come true?

• Bloody Mary, South Pacific

The only man I know who behaves sensibly is my tailor; he takes my measurements anew each time he sees me. The rest go on with their old measurements and expect me to fit them.

-- George Bernard Shaw, writer, Nobel laureate (1856-1950)

Edit: The full citation is to his 1903 play Man and superman: a comedy and a philosophy, where the character John Tanner ("M.I.R.C., Member of the Idle Rich Class") says:

Yes, because to be treated as a boy was to be taken on the old footing. I had become a new person ; and those who knew the old person laughed at me. The only man who behaved sensibly was my tailor : he took my measure anew every time he saw me, whilst all the rest went on with their old measurements and expected them to fit me.

There is an unfortunate optical illusion - a variant on the Doppler effect - that besets all frauds. It's unfortunate, because it has the effect of exacerbating the pecuniary losses that fraud victims endure, by unfairly leaving them, like many rape victims, irrationally ashamed of themselves.

The Doppler principle we posit holds that as a victim approaches a swindler, he sees nothing but green lights. But as soon as he realizes that his money is gone, he spins around and beholds, as if by magic, bright red flags as far as the eye can see.

-- Roger Parloff, senior editor, "More brazen than Madoff?", Fortune, 2009-03-31

[I]n my opinion nothing occurs contrary to nature except the impossible, and that never occurs.

-- Sagredo, "Two New Sciences" (1914 translation), Galileo Galilei

Nothing sucks more than that moment during an argument when you realize you're wrong.

-- Unknown