Not only a man's life, but his intellect too, may be possessed of a clear and definite character, so far as his intellect is applied to matters of theory. It is not every man, however, who has an intellect of this kind; for any such definite individuality as I mean is genius—an original view of the world, which presupposes an absolutely exceptional individuality, which is the essence of genius. A man's intellectual character is the theme on which all his works are variations. In an essay which I wrote in Weimar I called it the knack by which every genius produces his works, however various. This intellectual character determines the physiognomy of men of genius—what I might call the theoretical physiognomy—and gives it that distinguished expression which is chiefly seen in the eyes and the forehead. In the case of ordinary men the physiognomy presents no more than a weak analogy with the physiognomy of genius. On the other hand, all men possess the practical physiognomy, the stamp of will, of practical character, of moral disposition; and it shows itself chiefly in the mouth.