For to be possessed of a vigorous mind is not enough; the prime requisite is rightly to apply it. The greatest minds, as they are capable of the highest excellences, are open likewise to the greatest aberrations; and those who travel very slowly may yet make far greater progress, provided they keep always to the straight road, than those who, while they run, forsake it.

~René Descartes, Discourse on the Method

From desert cliff and mountaintop we trace the wide design,
Strike-slip fault and overthrust and syn and anticline...
We gaze upon creation where erosion makes it known,
And count the countless aeons in the banding of the stone.
Odd, long-vanished creatures and their tracks & shells are found;
Where truth has left its sketches on the slate below the ground.
The patient stone can speak, if we but listen when it talks.
Humans wrote the Bible; God wrote the rocks.

There are those who name the stars, who watch the sky by night,
Seeking out the darkest place, to better see the light.
Long ago, when torture broke the remnant of his will,
Galileo recanted, but the Earth is moving still.
High above the mountaintops, where only distance bars,
The truth has left its footprints in the dust between the stars.
We may watch and study or may shudder and deny,
Humans wrote the Bible; God wrote the sky.

By stem and root and branch we trace, by feather, fang and fur,
How the living things that are descend from things that were.
The moss, the kelp, the zebrafish, the very mice and flies,
These tiny, humble, wordless things--how shall they tell us lies?
We are kin to beasts; no other answer can we bring.
The truth has left its fingerprints on every living thing.
Remember, should you have to choose between them in the strife,
Humans wrote the Bible; God wrote life.

And we who listen to the stars, or walk the dusty grade,
Or break the very atoms down to see how they are made,
Or study cells, or living things, seek truth with open hand.
The profoundest act of worship is to try to understand.
Deep in flower and in flesh, in star and soil and seed,
The truth has left its living word for anyone to read.
So turn and look where best you think the story is unfurled.
Humans wrote the Bible; God wrote the world.

~Catherine Faber, The Word of God

There are times I almost think
Nobody sure of what he absolutely know
Everybody find confusion
In conclusion he concluded long ago
And it puzzle me to learn
That tho' a man may be in doubt of what he know,
Very quickly he will fight...
He'll fight to prove that what he does not know is so!

~ A Puzzlement, The King and I

I am still learning.

-- Michaelangelo's motto

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

Pope, Essay on Criticism

A book is a machine to think with.

I. A. Richards, "Principles of Literary Criticism"

Beware of no man more than of yourself; we carry our worst enemies within us.

Charles H. Spurgeon

The fact that I have no remedy for all the sorrows of the world is no reason for my accepting yours. It simply supports the strong probability that yours is a fake.

H.L. Mencken, Minority Report.

Not a quote about rationalism, but probably relevant to Less Wrong:

Pure Death

We looked, we loved, and therewith instantly

Death became terrible to you and me.

By love we disenthralled our natural terror

From every comfortable philosopher

Or tall, grey doctor of divinity:

Death stood at last in his true rank and order.

It happened soon, so wild of heart were we,

Exchange of gifts grew to a malady:

Their worth rose always higher on each side

Till there seemed nothing but ungivable pride

That yet remained ungiven, and this degree

Called a conclusion not to be denied.

Then we at last bethought ourselves, made shift

And simultaneously this final gift

Gave: each with shaking hands unlocks

The sinister, long, brass-bound coffin-box,

Unwraps pure death, with such bewilderment

As greeted our love's first accomplishment.

--Robert Graves

If, instead of welcoming inquiry and criticism, the admirers of a great author accept his writings as authoritative, both in their excellences and in their defects, the most serious injury is done to truth. In matters of philosophy and science, authority has ever been the great opponent of truth. A despotic calm is usually the triumph of error. In the republic of the sciences, sedition and even anarchy are beneficial in the long run to the greatest happiness of the greatest number.

William Stanley Jevons, Theory of Political Economy, 1871: p.275-6

Who has not experienced the chilling memory of the better things? How it creeps over the spirit of one's current dreams! Like the specter at the banquet it stands, its substanceless eyes viewing with a sad philosophy the make-shift feast.

-Theodore Dreiser, The Titan

Justice is an artefact of custom. Where customs are unsettled its dictates soon become dated. Ideas of justice are as timeless as fashions in hats.

-John Gray, Straw Dogs

David Hume was right to predict that superstition would survive for hundreds of years after his death, but how could he have anticipated that his own work would inspire Kant to invent a whole new package of superstitions? Or that the incoherent system of Marx would move vast populations to engineer their own ruin? Or that the infantile rantings of the author of Mein Kampf would be capable of bringing the whole world to war?

Perhaps we will one day succeed in immunizing our societies against such bouts of collective idiocy by establishing a social contract in which each child is systematically instructed in Humean skepticism. Such a new Emile would learn about the psychological weaknesses to which Homo sapiens is prey, and so would understand the wisdom of treating all authorities - political leaders and social role-models, academics and teachers, philosophers and prophets, poets and pop stars - as so many potential rogues and knoves, each out to exploit the universal human hunger for social status. He would therefore appreciate the necessity of doing all of his own thinking for himself. He would understand why and when to trust his neighbors. Above all, he would waste no time yearning for utopias that are incompatible with human nature.

-- Ken Binmore, in Natural Justice, p56

Getting caught up in style and throwing away victory is something for the lower ranks to do. Captains can't even think about doing such a carefree thing. Don't try to be a good guy. It doesn't matter who owes who. From the instant they enter into a war, both sides are evil.

• Shunsui Kyōraku Bleach

Related to: Politics, Protection

Rule I

We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances.

To this purpose the philosophers say that Nature does nothing in vain, and more is in vain when less will serve; for Nature is pleased with simplicity, and affects not the pomp of superfluous causes.

Rule II

Therefore to the same natural effects we must, as far as possible, assign the same causes.

As to respiration in a man and in a beast; the descent of stones in Europe and in America; the light of our culinary fire and of the sun; the reflection of light in the earth, and in the planets.

Rule III

The qualities of bodies, which admit neither intensification nor remission of degrees, and which are found to belong to all bodies within the reach of our experiments, are to be esteemed the universal qualities of all bodies whatsoever.

For since the qualities of bodies are only known to us by experiments, we are to hold for universal all such as universally agree with experiments; and such as are not liable to diminution can never be quite taken away. We are certainly not to relinquish the evidence for the sake of dreams and vain fictions of our own devising; nor are we to recede from the analogy of Nature, which is wont to be simple, and always consonant to itself. . .

Rule IV

In experimental philosophy we are to look upon propositions inferred by general induction from phenomena as accurately or very nearly true, notwithstanding any contrary hypotheses that may be imagined, till such time as other phenomena occur, by which they may either be made more accurate, or liable to exceptions.

This rule we must follow, that the argument of induction may not be evaded by hypotheses.

Isaac Newton, Philosophiae naturalis: Rules of Reasoning in Philosophy

Truth will sooner come out from error than from confusion.

Francis Bacon

If you are in a shipwreck and all the boats are gone, a piano top … that comes along makes a fortuitous life preserver. But this is not to say that the best way to design a life preserver is in the form of a piano top. I think that we are clinging to a great many piano tops in accepting yesterday’s fortuitous contrivings.

Buckminster Fuller

If you haven’t found something strange during the day, it hasn’t been much of a day.

John Archibald Wheeler

Go down deep enough into anything and you will find mathematics.

Dean Schlicter

Out-of-sample error equals in-sample error plus a penalty for model complexity

Y.S. Abu-Mostafa, in explaining the VC inequality of PAC learning.

If oxen and horses and lions had hands and were able to draw with their hands and do the same things as men, horses would draw the shapes of gods to look like horses and oxen to look like oxen, and each would make the gods’ bodies have the same shape as they themselves had.

Xenophanes

We're all puppets, Laurie. I'm just a puppet who can see the strings.

Dr. Manhattan (Watchmen)

Isaac Newton's argument for intelligent design:

Were all the planets as swift as Mercury or as slow as Saturn or his satellites; or were the several velocities otherwise much greater or less than they are (as they might have been had they arose from any other cause than their gravities); or had the distances from the centers about which they move been greater or less than they are (as they might have been had they arose from any other cause than their gravities); or had the quantity of matter in the sun or in Saturn, Jupiter, and the earth (and by consequence their gravitating power) been greater or less than it is; the primary planets could not have revolved about the sun nor the secondary ones about Saturn, Jupiter, and the earth, in concentric circles as they do, but would have moved in hyperbolas or parabolas or in ellipses very eccentric. To make this system, therefore, with all its motions, required a cause which understood and compared together the quantities of matter in the several bodies of the sun and planets and the gravitating powers resulting from thence.... And to compare and adjust all these things together in so great a variety of bodies, argues that cause to be, not blind and fortuitous, but very well skilled in mechanics and geometry.

-- Letter to Richard Bentley

"The best thing for being sad," replied Merlin, beginning to puff and blow, "is to learn something. That's the only thing that never fails. You may grow old and trembling in your anatomies, you may lie awake at night listening to the disorder of your veins, you may miss your only love, you may see the world about you devastated by evil lunatics, or know your honour trampled in the sewers of baser minds. There is only one thing for it then — to learn. Learn why the world wags and what wags it. That is the only thing which the mind can never exhaust, never alienate, never be tortured by, never fear or distrust, and never dream of regretting. Learning is the only thing for you. Look what a lot of things there are to learn."

— T.H. White (The Once and Future King)

There are more fools than knaves in the world, else the knaves would not have enough to live upon.

-Samuel Butler

All my confidence comes from knowing God's laws.

-- Talib Kweli (substitute "nature" for "God")

This is a bit long for a rationality quote and isn't really a quote but short enough and worth the read: The most poetic and convincing argument for striving for posthumanity (via aleph.se).

I just came across this and thought it was a pretty funny dialogue: "Reality is that which does not go away upon reprogramming." (Check the first 4 comments here: Chatbot Debates Climate Change Deniers on Twitter so You Don’t Have to)

This is of course a paraphrase borrowed from Philip K. Dick's famous statement:

Reality is that which, when you stop believing in it, doesn't go away.

The course of human progress staggers like a drunk; its steps are quick and heavy but its mind is slow and blunt

-Jesse Michaels of Operation Ivy

Posted because it's a useful and evocative metaphor: the drunk feels himself leaning or falling in one direction, and puts his foot down in that direction to steady himself. If he doesn't step far enough, he is still leaning in the same direction, and he steps again. In this way we can make fantastic progress in directions we don't like while getting further away from the ways we did want to go.

Man, I'm amazing! I'm a machine that turns FOOD into IDEAS!

-- T-Rex, Dinosaur Comics #539

Many a man has cherished for years as his hobby some vague shadow of an idea, too meaningless to be positively false; he has, nevertheless, passionately loved it, has made it his companion by day and by night, and has given to it his strength and his life, leaving all other occupations for its sake, and in short has lived with it and for it, until it has become, as it were, flesh of his flesh and bone of his bone; and then he has waked up some bright morning to find it gone, clean vanished away like the beautiful Melusina of the fable, and the essence of his life gone with it. I have myself known such a man; and who can tell how many histories of circle-squarers, metaphysicians, astrologers, and what not, may not be told in the old German story?

Charles Sanders Peirce

It is still an unending source of surprise for me how a few scribbles on a blackboard or on a piece of paper can change the course of human affairs. -Stanislaw Ulam

It is a profound and necessary truth that the deep things in science are not found because they are useful, they are found because it was possible to find them. -J. Robert Oppenheimer.

"However insistently the blind may deny the existence of the sun, they cannot annihilate it. " - D. T. Suzuki

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Kołakowski's Law, or The Law of the Infinite Cornucopia:

For any given doctrine that one wants to believe, there is never a shortage of arguments by which to support it.

Leszek Kołakowski

We are at the very beginning of time for the human race. It is not unreasonable that we grapple with problems. But there are tens of thousands of years in the future. Our responsibility is to do what we can, learn what we can, improve the solutions, and pass them on.

Richard Feynman

A horse that can count to ten is a remarkable horse, not a remarkable mathematician.
--Samuel Johnson

If you can't tell whose side someone is on, they are not on yours. -Warren E. Buffett