A doctor who doesn't say too many foolish things is a patient half-cured. (1921)

A fool must now and then be right, by chance

A fool, Mr, Edgeworth, is one who has never made an experiment.

Any fool can destroy trees. They cannot run away; and if they could, they would still be destroyed,—chased and hunted down as long as fun or a dollar could be got out of their bark hides, branching horns, or magnificent bole backbones. Few that fell trees plant them; nor would planting avail much towards getting back anything like the noble primeval forests. During a man's life only saplings can be grown, in the place of the old trees—tens of centuries old—that have been destroyed.

Any man who does not make himself proficient in at least two languages other than his own is a fool.

Classification is now a pejorative statement. You know, these classifiers look like “dumb fools.” I’m a classifier. But I’d like to use a word that includes more than what people consider is encompassed by classification. It is more than that, and it’s something which can be called phenomenology.

Examinations are formidable even to the best prepared, for the greatest fool may ask more than the wisest man can answer.

Experience of actual fact either teaches fools or abolishes them.

He who knows not, and knows not he knows not, he is a fool—shun him;
He who knows not, and knows he knows not, he is simple—teach him;
He who knows, and knows not he knows, he is asleep—wake him;
He who knows, and knows he knows, he is wise—follow him.

He's a Fool that makes his Doctor his Heir.

Heraldry has been contemptuously termed 'the science of fools with long memories.'

I happen to be a kind of monkey. I have a monkeylike curiosity that makes me want to feel, smell, and taste things which arouse my curiosity, then to take them apart. It was born in me. Not everybody is like that, but a scientific researchist should be. Any fool can show me an experiment is useless. I want a man who will try it and get something out of it.

I think that I shall never see
A poem as lovely as a tree.
A tree whose hungry mouth is prest
Against the earth's sweet flowing breast;
A tree that looks at God all day,
And lifts her leafy arms to pray;
A tree that may in Summer wear
A nest of robins in her hair;
Upon whose bosom snow has lain;
Who intimately lives with rain.
Poems are made by fools like me,
But only God can make a tree.

If all boys could be made to know that with every breath of cigarette smoke they inhale imbecility and exhale manhood ... and that the cigarette is a maker of invalids, criminals and fools—not men—it ought to deter them some. The yellow finger stain is an emblem of deeper degradation and enslavement than the ball and chain.

If our intention had been merely to bring back a handful of soil and rocks from the lunar gravel pit and then forget the whole thing, we would certainly be history's biggest fools. But that is not our intention now—it never will be. What we are seeking in tomorrow’s [Apollo 11]trip is indeed that key to our future on earth. We are expanding the mind of man. We are extending this God-given brain and these God-given hands to their outermost limits and in so doing all mankind will benefit. All mankind will reap the harvest…. What we will have attained when Neil Armstrong steps down upon the moon is a completely new step in the evolution of man.

In reality, all arguments from experience are founded on the similarity which we discover among natural objects, and by which we are induced to expect effects similar to those which we have found to follow from such objects. And though none but a fool or madman will ever pretend to dispute the authority of experience, or to reject that great guide of human life, it may surely be allowed a philosopher to have so much curiosity at least as to examine the principle of human nature, which gives this mighty authority to experience, and makes us draw advantage from that similarity which nature has placed among different objects. From causes which appear similar we expect similar effects. This is the sum of our experimental conclusions.

Intelligence is an extremely subtle concept. It's a kind of understanding that flourishes if it's combined with a good memory, but exists anyway even in the absence of good memory. It's the ability to draw consequences from causes, to make correct inferences, to foresee what might be the result, to work out logical problems, to be reasonable, rational, to have the ability to understand the solution from perhaps insufficient information. You know when a person is intelligent, but you can be easily fooled if you are not yourself intelligent.

It is better to be a human being dissatisfied than a pig satisfied; better to be Socrates dissatisfied than a fool satisfied.

Logical consequences are the scarecrows of fools and the beacons of wise men.

Never fear big long words.
Big long words name little things.
All big things have little names.
Such as life and death, peace and war.
Or dawn, day, night, hope, love, home.
Learn to use little words in a big way.
It is hard to do,
But they say what you mean.
When you don't know what you mean, use big words.
That often fools little people.

Science is a way to not fool ourselves.

Scientists are the easiest to fool. ... They think in straight, predictable, directable, and therefore misdirectable, lines. The only world they know is the one where everything has a logical explanation and things are what they appear to be. Children and conjurors—they terrify me. Scientists are no problem; against them I feel quite confident.

The average gambler will say “The player who stakes his whole fortune on a single play is a fool, and the science of mathematics can not prove him to be otherwise.” The reply is obvious: “The science of mathematics never attempts the impossible, it merely shows that other players are greater fools.”
[Concluding remarks to his mathematical proof, with certain assumptions, that a gambler's best strategy would be to always make his largest stake on his first play.]

The Nobel Prize gives you an opportunity to make a fool of yourself in public.

There are no foolish questions and no man becomes a fool until he has stopped asking questions.

This is the excellent foppery of the world: that when we are sick in fortune—often the surfeits of our own behaviour—we make guilty of our disasters the sun, the moon, and stars, as if we were villains on necessity, fools by heavenly compulsion, knaves, thieves, and treachers by spherical predominance, drunkards, liars, and adulterers, by an enforced obedience of planetary influence, and all that we are evil in, by a divine thrusting on. An admirable evasion of whoremaster man, to lay his goatish disposition on the charge of a star! My father compounded with my mother under the Dragon's tail and my nativity was under Ursa Major, so that it follows that I am rough and lecherous. Fut! I should have been that I am had the maidenliest star in the firmament twinkled on my bastardizing.

Through our scientific and technological genius we've made of this world a neighborhood. And now through our moral and ethical commitment we must make of it a brotherhood. We must all learn to live together as brothers—or we will all perish together as fools.

You can be a thorough-going Neo-Darwinian without imagination, metaphysics, poetry, conscience, or decency. For 'Natural Selection' has no moral significance: it deals with that part of evolution which has no purpose, no intelligence, and might more appropriately be called accidental selection, or better still, Unnatural Selection, since nothing is more unnatural than an accident. If it could be proved that the whole universe had been produced by such Selection, only fools and rascals could bear to live.

You can't possibly be a scientist if you mind people thinking that you're a fool.