A man who thinks himself a chicken is to himself as ordinary as a chicken. A man who thinks he is a bit of glass is to himself as dull as a bit of glass. It is the homogeneity of his mind which makes him dull, and which makes him mad.Here, by 'makes', G K Chesterton is talking not of efficient but of formal causation: mental homogeneity is a criterion of insanity. The statement is (not atypically) both overblown and underdetermined, but we get a clearer idea of what he meant as we read on:
Now, if we are to glance at the philosophy of sanity, the first thing to do in the matter is to blot out one big and common mistake. There is a notion adrift everywhere that imagination, especially mystical imagination, is dangerous to man's mental balance. Poets are commonly spoken of as psychologically unreliable; and generally there is a vague association between wreathing laurels in your hair and sticking straws in it. Fact and history utterly contradict this view. Most of the very great poets have been not only sane, but extremely business-like... Imagination does breed insanity. Exactly what does breed insanity is reason. Poets do not go mad; but chess players do. Mathematicians go mad, and cashiers; but creative artists very seldom.Does this not seem peculiar? Is not unreason another name for madness? Chesterton clarifies:
I am not, as will be seen, in any sense attacking logic; I only say that this danger does lie in logic, not in imagination. .... Poetry is sane because it floats easily in an infinite sea; reason seeks to cross the infinite sea, and so make it finite. The result is mental exhaustion... The poet only desires exaltation and expansion, a world to stretch himself in. The poet only asks to get his head into the heavens. It is the logician who seeks to get the heavens into his head. And it is his head that splits.Perhaps what he is saying would be better put in terms of an over-extension, an immodesty, of reason's application being what makes for insanity. (Think: Minkowski on the morbid rationalism and morbid geometrism found in schizophrenia.) This is born out by what follows:
We have all heard people cite the celebrated line of Dryden as "Great genius is to madness near allied." But Dryden did not say [this]. Dryden was a great genius himself, and knew better. It would have been hard to find a man more romantic than he, or more sensible. What Dryden said was this, "Great wits are oft to madness near allied"; and that is true. ... He was talking of a cynical man of the world, a skeptic, a diplomatist, a great practical politician. Such men are indeed to madness near allied. Their incessant calculation of their own brains and other people's brains is a dangerous trade. It is always perilous to the mind to reckon up the mind.Sanity, as Chesterton sees it, involves knowing when not to think. Consider:
the minor acts of a healthy man: whistling as he walks, slashing the grass with a stick; kicking his heels or rubbing his hands. It is the happy man who does the useless things; the sick man is not strong enough to be idle. ... the madman... generally sees too much cause in everything. The madman would read a conspiratorial significance into those empty activities. He would think that the lopping of the grass was an attack on private property. He would think that the kicking of the heels was a signal to an accomplice. If the madman could for an instant become careless, he would become sane.Although Chesterton puts it in a psychological register, I suspect the point is better grasped as logical. (Think of Wittgenstein in On Certainty: we do not doubt the hinge propositions and, in fact: one would have to be mad to do so.)
Here's his most striking pronouncement:
If you argue with a madman, it is extremely probable that you will get the worst for it; for in many ways his mind moves all the quicker for not being delayed by the things that go with good judgement. He is not hampered by a sense of humor or by charity, or by the dumb certainties of experience. He is the more logical for losing certain sane affections. Indeed the common phrase for insanity is in this respect a misleading one. The madman is not the man who has lost his reason. The madman is the man who has lost everything except his reason.
The man who cannot believe his senses, and the man who cannot believe anything else, are both insane, but their insanity is proud not by any error in their argument, but by the manifest mistake of their whole lives. ... [The] chief mark and element of insanity ... in summary ... is reason used without root, reason in the void. The man who begins to think without the proper first principles goes mad; he begins to think at the wrong end.Chesterton's recipe for therapeutics is surprising, but this is but a function of his rhetoric. The following makes this clear, and also speaks for itself:
Mysticism keeps men sane. As long as you have mystery you have health; when you destroy mystery you create morbidity. The ordinary man has always been sane because the ordinary man has always been a mystic. ... He has always cared more for truth than for consistency. If he saw two truths that seemed to contradict each other, he would take the two truths and the contradiction along with them. ... Thus he has always believed that there was such a thing as fate, but such a thing as free will also. ... He admired youth because it was young and age because it was not. It is exactly this balance of apparent contradictions that has been the whole buoyancy of the healthy man. The whole secret of mysticism is this: that man can understand everything by the help of what he does not understand. The morbid logician seeks to make everything lucid, and succeeds in making everything mysterious. The mystic allows one thing to be mysterious, and everything else becomes clear. ... The one created thing which we cannot look at is the one thing in the light of which we look at everything.