“For every animal, and more especially for man, a certain conformity and proportion between the will and the intellect is necessary for existing or making any progress in the world. The more precise and correct the proportion which nature establishes, the more easy, safe and agreeable will be the passage through the world. Still, if the right point is only approximately reached, it will be enough to ward off destruction. There are, then, certain limits within which the said proportion may vary, and yet preserve a correct standard of conformity. The normal standard is as follows. The object of the intellect is to light and lead the will on its path, and therefore, the greater the force, impetus and passion, which spurs on the will from within, the more complete and luminous must be the intellect which is attached to it, that the vehement strife of the will, the glow of passion, and the intensity of the emotions, may not lead man astray, or urge him on to ill considered, false or ruinous action; this will, inevitably, be the result, if the will is very violent and the intellect very weak. On the other hand, a phlegmatic character, a weak and languid will, can get on and hold its own with a small amount of intellect; what is naturally moderate needs only moderate support. The general tendency of a want of proportion between the will and the intellect, in other words, of any variation from the normal proportion I have mentioned, is to produce unhappiness, whether it be that the will is greater than the intellect, or the intellect greater than the will. Especially is this the case when the intellect is developed to an abnormal degree of strength and superiority, so as to be out of all proportion to the will, a condition which is the essence of real genius; the intellect is then not only more than enough for the needs and aims of life, it is absolutely prejudicial to them. The result is that, in youth, excessive energy in grasping the objective world, accompanied by a vivid imagination and a total lack of experience, makes the mind susceptible, and an easy prey to extravagant ideas, nay, even to chimeras; and the result is an eccentric and phantastic character. And when, in later years, this state of mind yields and passes away under the teaching of experience, still the genius never feels himself at home in the common world of every day and the ordinary business of life; he will never take his place in it, and accommodate himself to it as accurately as the person of moral intellect; he will be much more likely to make curious mistakes. For the ordinary mind feels itself so completely at home in the narrow circle of its ideas and views of the world that no one can get the better of it in that sphere; its faculties remain true to their original purpose, viz., to promote the service of the will; it devotes itself steadfastly to this end, and abjures extravagant aims. The genius, on the other hand, is at bottom a monstrum per excessum; just as, conversely, the passionate, violent and unintelligent man, the brainless barbarian, is a monstrum per defectum”.
From Psychological Observations, translated by T. Bailey Saunders