Aristotle, Politics

[1255a] [1] It is manifest therefore that there are cases of people of whom some are freemen and the others slaves by nature, and for these slavery is an institution both expedient and just. But at the same time it is not difficult to see that those who assert the opposite are also right in a manner. The fact is that the terms ‘slavery’ and ‘slave’ are ambiguous; for there is also such a thing as a slave or a man that is in slavery by law, for the law is a sort of agreement under which the things conquered in war are said to belong to their conquerors. Now this conventional right is arraigned by many jurists just as a statesman is impeached for proposing an unconstitutional measure; they say that it is monstrous if the person powerful enough to use force, and superior in power, is to have the victim of his force as his slave and subject; and even among the learned some hold this view, though others hold the other. But the reason of this dispute and what makes the theories overlap is the fact that in a certain manner virtue when it obtains resources has in fact very great power to use force, and the stronger party always possesses superiority in something that is good,¹ so that it is thought that force cannot be devoid of goodness, but that the dispute is merely about the justice of the matter （for it is due to the one party holding that the justification of authority is good-will, while the other identifies justice with the mere rule of the stronger）; because obviously if these theories be separated apart, [20] the other theories have no force or plausibility at all, implying that the superior in goodness has no claim to rule and be master. But some persons, simply clinging, as they think, to principle of justice （for the law is a principle of justice）, assert that the enslavement of prisoners of war is just; yet at the same time they deny the assertion, for there is the possibility that wars may be unjust in their origin and one would by no means admit that a man that does not deserve slavery can be really a slave—otherwise we shall have the result that persons reputed of the highest nobility are slaves and the descendants of slaves if they happen to be taken prisoners of war and sold. Therefore they do not mean to assert that Greeks themselves if taken prisoners are slaves, but that barbarians are. Yet when they say this, they are merely seeking for the principles of natural slavery of which we spoke at the outset; for they are compelled to say that there exist certain persons who are essentially slaves everywhere and certain others who are so nowhere. And the same applies also about nobility: our nobles consider themselves noble not only in their own country but everywhere, but they think that barbarian noblemen are only noble in their own country—which implies that there are two kinds of nobility and of freedom, one absolute and the other relative, as Helen says in Theodectes²: “ But who would dare to call me menial,
The scion of a twofold stock divine?
” Yet in so speaking they make nothing but virtue and vice the distinction between slave and free, the noble and the base-born;