The moral being of man, a prey to internal discord, may be said to be quartered, because the four primary faculties of the soul and mind of man — Understanding and Will, Reason and Imagination, stand in a twofold opposition one to the other, and are, if we may so speak, dispersed into the four regions of existence. Reason in man is the regulating faculty of thought; and so far it occupies the first place in life and the whole system and arrangement of life; but it is unproductive in itself, and even in science it can; pretend to no real fertility or immediate intuition. Imagination on the other hand is fertile and inventive indeed, but left to itself and without guidance, it is blind, and consequently subject to illusion. The best will, devoid of discernment and understanding, can accomplish little good. Still less capable of good is a strong, and even the strongest understanding, when coupled with a wicked and corrupt character; or should such an understanding be associated with an unsteady and changeable will, the individual destitute of character, is entirely without influence.
Schlegel, The Philosophy of History, vol 1, Robertson, tr., p. 169. Schlegel goes on to argue (p. 170):
As in the intellectual character of particular men, or in any given system of human thought, fiction, or science (and these can be better described and more closely analyzed than the fleeting and transient phenomena of real life and the social relations); as in every such individual production, I say, of human thought and human action, either Reason will preponderate as a systematic methodizer and a moral regulator, or a fertile, inventive Imagination will be displayed, or a clear, penetrative understanding, or again a peculiar energy of will and strength of character will be observed; so the same holds good in the great whole of universal history — in the moral and intellectual existence — the character, or the mind of particular ages or nations in the ancient world.
Each human capacity is essential to a fully human life, but each is capable of undergoing a pathological overgrowth. Reason when pathologically dominating the other three, for instance, drives toward excessive distinction, divisiveness, sectarianism, arbitrariness of system; Imagination, required not merely for fiction but also for scientific discovery, becomes crowded out by technicalities; formulae become more important than understanding; procedures become more important than character. Similar kinds of aberrations occur with the overdominance of each of the other three.