Yet there _was_ a difference between them, marking off each as the head of a whole School much wider than the Academy or the Lyceum; a difference which we can best express by saying that Plato was pre-eminently a practical, Aristotle pre-eminently a speculative genius. The object of the one was to reorganise all human life, that of the other to reorganise all human knowledge. Had the one lived earlier, he would more probably have been a great statesman or a great general than a great writer; the other would at no time have been anything but a philosopher, a mathematician, or a historian. Even from birth they seemed to be respectively marked out for an active and for a contemplative life: the one, a citizen of the foremost State in Hellas, sprung from a family in which political ambition was hereditary, himself strong, beautiful, fascinating, eloquent, and gifted with the keenest insight into men’s capacities and motives; the other a Stagirite and an Asclepiad, that is to say, without opportunities for a public career, and possessing a hereditary aptitude for anatomy and natural history, fitted by his insignificant person and delicate constitution for sedentary pursuits, and better able to acquire a knowledge even of human nature from books than from a living converse with men and affairs. Of course, we are not for a moment denying to Plato a foremost place among the masters of those who know; he embraced all the science of his age, and to a great extent marked out the course which the science of future ages was to pursue; nevertheless, for him, knowledge was not so much an end in itself as a means for the attainment of other ends, among which the preservation of the State seems to have been, in his eyes, the most important.[M] Aristotle, on the other hand, after declaring happiness to be the supreme end, defines it as an energising of man’s highest nature, which again he identifies with the reasoning process or cognition in its purest form.