Barbarians were slaves by nature. Hence it was right for the Greeks to make war on them and reduce them to slavery, because “for that end they were born.”[507] Plato had in his _Laws_ accepted slavery as a political necessity; Aristotle proclaimed it as a part of the natural order of things. This doctrine had far-reaching historical consequences. Aristotle’s declaration that slaves are merely animated instruments, are men incapable of virtue, worked as powerfully in destroying ancient slavery as the _obiter dictum_ of Chief Justice Taney of the Supreme Court of the United States, in the Dred Scott case, that negro slaves have no rights which the white man is bound to respect, worked for the destruction of negro slavery in the Southern states. For, as Professor Denis says, by pushing too far the argument, by founding slavery on natural right, Aristotle provoked thought and protest, and led the Stoics to reject with indignation his theories and to proclaim the moral equality of master and slave, of Greek and barbarian.[508] Aristotle’s ethics exercised very little influence either upon the actual moral life or the ethical speculations of antiquity; but in the medieval time it came to exert a profound influence upon Christian ethics.[509] The schoolmen made it the trunk into which they grafted Christian morals--with incongruous results, as we shall see later. [Sidenote: Decay of the Greek city state and the accompanying decay of the Greek ideal of character] The political revolution in Hellas in the fourth century B.C. had deep import for Greek morality. That century saw the triumph of Macedonia over the Greek cities. This meant the triumph of despotic monarchy over city democracy. This revolution in the political realm meant a great revolution in the realm of morals, for the reason that, as we have seen, the old Greek ideal of excellence was largely based upon the relation of the individual to the state. With the loss of Greek liberty the very basis of the Greek ideal of character was removed, and the virtues of the type tended to disappear.[510]