The end for which the state exists is not merely its own self-perpetuation. As we have seen, Aristotle assigns a higher value to the life of the student than to the life of practical affairs. Since it is only in the civilised state that the student can pursue his vocation, the ultimate reason for which the state exists is to educate its citizens in such a way as shall fit them to make the noble use of leisure. In the end the state itself is a means to the spiritual cultivation of its individual members. This implies that the chosen few, who have a vocation to make full use of the opportunities provided for leading this life of noble leisure, are the real end for the sake of which society exists. The other citizens who have no qualification for any life higher than that of business and affairs are making the most of themselves in devoting their lives to the conduct and maintenance of the organisation whose full advantages they are unequal to share in. It is from this point of view also that Aristotle treats the social problem of the existence of a class whose whole life is spent in doing the hard work of society, and thus setting the citizen body free to make the best use it can of leisure. In the conditions of life in the Greek world this class consisted mainly of slaves, and thus the problem Aristotle has to face is the moral justifiability of slavery. We must remember that he knew slavery only in its comparatively humane Hellenic form. The slaves of whom he speaks were household servants and assistants in small businesses. He had not before his eyes the system of enormous industries carried on by huge gangs of slaves under conditions of revolting degradation which disgraced the later Roman Republic and the early Roman Empire, or the Southern States of North America. His problems are in all essentials much the same as those which concern us to-day in connection with the social position of the classes who do the hard bodily work of the community.