Aristotle's attitude to the practical life is also dependent on Plato's. In the Tenth Book of the _Ethics_ he puts the claims of the Contemplative Life even higher than Plato ever did, so that the practical life appears to be only ancillary to it. He does not feel in the same degree as Plato the call for the philosopher to descend once more into the Cave for the sake of the prisoners there, and altogether he seems far more indifferent to the practical interests of life. Nevertheless he followed Plato's lead in giving much of his time to the study of Politics and that too with the distinctly practical aim of training legislators. He has often been criticized for his failure to see that the days of the city-state were numbered, and for the way in which he ignores the rise of an imperial monarchy in the person of his own pupil Alexander the Great. That, however, is not quite fair. Aristotle had a healthy dislike of princes and courts, and the city-state still appealed to him as the normal form of political organization. He could not believe that it would ever be superseded, and he wished to contribute to its better administration. He had, in fact, a much more conservative outlook than Plato, who was inclined to think with Isocrates, that the revival of monarchy was the only thing that could preserve Hellenism as things were then. We must remember that Aristotle was not himself a citizen of any free state, and that he could hardly be expected to have the same political instincts as Plato, who belonged by birth to the governing classes of Athens and had inherited the liberal traditions of the Periclean Age. This comes out best of all perhaps, in the attitude of the two philosophers to the question of slavery. In the _Laws_, which deals with existing conditions, Plato of course recognizes the _de facto_ existence of slavery, though he is very sensible of its dangers and makes many legislative proposals with a view to their mitigation. In the _Republic_, on the other hand, where there is no need to trouble about existing conditions, he makes Socrates picture for us a community in which there are apparently no slaves at all. Aristotle is also anxious to mitigate the worst abuses of slavery, but he justifies the institution as a permanent one by the consideration that barbarians are 'slaves by nature' and that it is for their own interest to be 'living tools'. This insistence upon the fundamental distinction between Greeks and barbarians must have seemed an anachronism to many of Aristotle's contemporaries and it had been expressly denounced by Plato as unscientific.