"Mad, adj. Affected with a high degree of intellectual independence; not conforming to standards of thought, speech, and action derived by the conformants from study of themselves; at odds with the majority; in short, unusual. It is noteworthy that persons are pronounced mad by officials destitute of evidence that they themselves are sane."

"Love: A temporary insanity curable by marriage or by removal of the patient from the influences under which he incurred the disorder. This disease is prevalent only among civilized races living under artificial conditions; barbarous nations breathing pure air and eating simple food enjoy immunity from its ravages. It is sometimes fatal, but more frequently to the physician than to the patient."

"In your day, riches debauched one class with idleness of mind and body, while poverty sapped the vitality of the masses by overwork, bad food, and pestilent homes. The... burdens laid on women, enfeebled the very springs of life. Instead of these maleficent circumstances, all now enjoy the most favorable conditions of physical life; the young are carefully nurtured and studiously cared for; the labor which is required of all is limited to the period of greatest bodily vigor, and is never excessive; care for one's self and one's family, anxiety as to livelihood, the strain of a ceaseless battle for life—all these influences, which once did so much to wreck the minds and bodies of men and women, are known no more. Certainly, an improvement of the species ought to follow such a change. Insanity, for instance, which in the nineteenth century was so terribly common a product of your insane mode of life, has almost disappeared, with its alternative, suicide."

"All schizophrenia patients are mad, and none are sane. Their behaviour is incomprehensible. It tells us nothing about what they do in the rest of their lives, gives no insight into the human condition and has no lesson for sane people except how sane they are. There's nothing profound about it. Schizophrenics aren't clever or wise or witty — they may make some very odd remarks but that's because they're mad, and there's nothing to be got out of what they say. When they laugh at things the rest of us don't think are funny, like the death of a parent, they're not being penetrating, and on other occasions they're not wryly amused at at the simplicity and stupidity of the psychiatrist, however well justified that might be in many cases. They're laughing because they're mad, too mad to be able to tell what's funny any more. The rewards for being sane may not be very many but knowing what's funny is one of them. And that's an end of the matter."

"Only a madman would claim that there is some thing unreal about reality."

"Have I need of mad men, that ye have brought this fellow to play the mad man in my presence?"

"Our No. 1 enemy is ignorance. And I believe that is the No. 1 enemy for everyone — it's not understanding what actually is going on in the world."

"Credulity and confidence are the constant companions of ignorance."

"To be ignorant of one's ignorance is the malady of the ignorant."

"Namque inscitia est, Adversum stimulum calces."

"Ita me dii ament, ast ubi sim nescio."

"Homine imperito nunquam quidquid injustius, Qui nisi quod ipse facit nihil rectum putat."

"Omne ignotum pro magnifico est."

"The more we study, we the more discover our ignorance."

"Illi mors gravis incubat qui notus nimis omnibus ignotus moritur sibi."

"Etiam illud quod scies nesciveris; Ne videris quod videris."

"It is better to be unborn than untaught: for ignorance is the root of misfortune."

"Quod latet ignotum est; ignoti nulla cupido."

"But let a man know that there are things to be known, of which he is ignorant, and it is so much carved out of his domain of universal knowledge."

"The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents. We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far. The sciences, each straining in its own direction, have hitherto harmed us little; but some day the piecing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we shall either go mad from the revelation or flee from the light into the peace and safety of a new dark age."

"A man may live long, and die at last in ignorance of many truths, which his mind was capable of knowing, and that with certainty."

"Rien n'est si dangereux qu'un ignorant ami: Mieux vaudrait un sage ennemi."

"It was a childish ignorance, But now 'tis little joy To know I'm further off from heaven Than when I was a boy."

"Who ne'er knew salt, or heard the billows roar."

"Es ist nichts schrecklicher als eine thätige Unwissenheit."

"Often the cock-loft is empty, in those whom nature hath built many stories high."

"Ignorance seldom vaults into knowledge, but passes into it through an intermediate state of obscurity, even as night into day through twilight."

"Non me pudet fateri nescire quod nesciam."

"Ignoratione rerum bonarum et malarum maxime hominum vita vexatur."

"Causarum ignoratio in re nova mirationem facit."

"Don't be in such a hurry to condemn a person because he doesn't do what you do, or think as you think or as fast. There was a time when you didn't know what you know today."

"Ignorance of each other is what has made unity impossible in the past. Therefore we need enlightenment. We need more light about each other. Light creates understanding, understanding creates love, love creates patience, and patience creates unity. Once we have more knowledge (light) about each other, we will stop condemning each other and a United front will be brought about."

"I do not approve of anything that tampers with natural ignorance. Ignorance is like a delicate exotic fruit; touch it and the bloom is gone. The whole theory of modern education is radically unsound. Fortunately in England, at any rate, education produces no effect whatsoever. If it did, it would prove a serious danger to the upper classes, and probably lead to acts of violence in Grosvenor Square."

"Ignorance served no useful purpose; it changed no fact, it offered no shelter."

"The days of deadly ignorance will end, and they will end soon."

"How can he remember well his ignorance—which his growth requires—who has so often to use his knowledge?"

"We struggle onward, ignorant and blind,"

"Blind and naked Ignorance Delivers brawling judgments, unashamed, On all things all day long."

"Ignorance is the mother of devotion."

"Ignoramuses are numerous in the palace."

"There's nothing as safe as ignorance — or as dangerous."

"Ignorantia non est argumentum."

"Ignorant men Don't know what good they hold in their hands until They've flung it away."

"If one neglects the laws of learning, a sentence is imposed that he is forever chained to his ignorance."

"[[Game theory|[G]ame theory]] has already established itself as an essential tool in the , where it is widely regarded as a unifying language for investigating human behavior. Game theory's prominence in evolutionary biology builds a natural bridge between the life sciences and the behavioral sciences. And connections have been established between game theory and the two most prominent pillars of physics: and quantum theory. ...[M]any physicists, neuroscientists, and social scientists... are... pursuing the dream of a quantitative science of human behavior. Game theory is showing signs of... an increasing important role in that endeavor. It's a story of exploration along the shoreline separating the continent of knowledge from an ocean of ignorance... a story worth telling."

"Madam, thou errest: I say, there is no darkness, but ignorance; in which thou art more puzzled, than the Egyptians in their fog."