a higher plane than free artisans, in that he denies virtue to such classes, since it cannot be produced in them, except as they are brought into contact with a master.666 He thus makes slavery a humanitarian institution, and the slave a real member of the family.667 But the admission most fatal to his theory is in agreeing that the slave qua man may be a subject of friendship,668 and in advocating his manumission as a reward for good behavior. With this, the attempted distinction between him, qua slave and qua man, utterly breaks down, and the existence of natural slaves is virtually denied.669 Thus the great champion of slavery in the ancient world, by his very defense of it, repudiates its right as a natural institution. His actual conception of the relation is, indeed, not far from the ideal of Plato, a union for the best mutual service of rulers and ruled, in which the slave receives from his master a moral exchange value for his physical service.670
There is a certain economic and moral truth, also, in the attitude of Aristotle toward slavery, that, as Ruskin has observed,671 higher civilization