What is madness? To have erroneous perceptions, and to reason correctly from them? Let the wisest man, if he would understand madness, attend to the succession of his ideas while he dreams. If he be troubled with indigestion during the night, a thousand incoherent ideas torment him; it seems as if nature punished him for having taken too much food, or for having injudiciously selected it, by supplying involuntary conceptions; for we think but little during sleep, except when annoyed by a bad digestion. Unquiet dreams are in reality a transient madness.

Madness is a malady which necessarily hinders a man from thinking and acting like other men. Not being able to manage property, the madman is withheld from it; incapable of ideas suitable to society, he is shut out from it; if he be dangerous, he is confined altogether; and if he be furious, they bind him. Sometimes he is cured by baths, by bleeding, and by regimen.

This man is not, however, deprived of ideas; he frequently possesses them like other men, and often when he sleeps. We might inquire how the spiritual and immortal soul, lodged in his brain, receives all its ideas correctly and distinctly, without the capacity of judgment. It perceives objects, as the souls of Aristotle, of Plato, of Locke, and of Newton, perceived them. It hears the same sounds, and possesses the same sense of feeling — how therefore, receiving impressions like the wisest, does the soul of the madman connect them extravagantly, and prove unable to disperse them?

If this simple and eternal substance enjoys the same properties as the souls which are lodged in the sagest brains, it ought to reason like them. Why does it not? If my madman sees a thing red, while the wise men see it blue; if when my sages hear music, my madman hears the braying of an ass; if when they attend a sermon, he imagines himself to be listening to a comedy; if when they understand yes, he understands no; then I conceive clearly that his soul ought to think contrary to theirs. But my madman having the same perceptions as they have, there is no apparent reason why his soul, having received all the necessary materials, cannot make a proper use of them. It is pure, they say, and subject to no infirmity; behold it provided with all the necessary assistance; nothing which passes in the body can change its essence; yet it is shut up in a close carriage, and conveyed to Charenton.

This reflection may lead us to suspect that the faculty of thought, bestowed by God upon man, is subject to derangement like the other senses. A madman is an invalid whose brain is diseased, while the gouty man is one who suffers in his feet and............