Aristotle raises the question of whether slavery is natural or conventional. He asserts that the former is the case. So, Aristotle's theory of slavery holds that some people are naturally slaves and others are naturally masters. Thus he says:
But is there any one thus intended by nature to be a slave, and for whom such a condition is expedient and right, or rather is not all slavery a violation of nature?
There is no difficulty in answering this question, on grounds both of reason and of fact. For that some should rule and others be ruled is a thing not only necessary, but expedient; from the hour of their birth, some are marked out for subjection, others for rule.
This suggests that anyone who is ruled must be a slave, which does not seem at all right. Still, given that this is so he must state what characteristics a natural slave must have -- so that he or she can be recognized as such a being. Who is marked out for subjugation, and who for rule? This is where the concept of "barbarian" shows up in Aristotle's account. Aristotle says:
But among barbarians no distinction is made between women and slaves, because there is no natural ruler among them: they are a community of slaves, male and female. Wherefore the poets say,It is meet that Hellenes should rule over barbarians;as if they thought that the barbarian and the slave were by nature one.
So men rule naturally over women, and Greeks over barbarians! But what is it which makes a barbarian a slave? Here is what Aristotle says:
Where then there is such a difference as that between soul and body, or between men and animals (as in the case of those whose business is to use their body, and who can do nothing better), the lower sort are by nature slaves, and it is better for them as for all inferiors that they should be under the rule of a master. For he who can be, and therefore is, another's and he who participates in rational principle enough to apprehend, but not to have, such a principle, is a slave by nature. Whereas the lower animals cannot even apprehend a principle; they obey their instincts. And indeed the use made of slaves and of tame animals is not very different; for both with their bodies minister to the needs of life. Nature would like to distinguish between the bodies of freemen and slaves, making the one strong for servile labor, the other upright, and although useless for such services, useful for political life in the arts both of war and peace. But the opposite often happens--that some have the souls and others have the bodies of freemen. And doubtless if men differed from one another in the mere forms of their bodies as much as the statues of the Gods do from men, all would acknowledge that the inferior class should be slaves of the superior. And if this is true of the body, how much more just that a similar distinction should exist in the soul? but the beauty of the body is seen, whereas the beauty of the soul is not seen. It is clear, then, that some men are by nature free, and others slaves, and that for these latter slavery is both expedient and right.
So the theory is that natural slaves should have powerful bodies but be unable to rule themselves. Thus, they become very much like beasts of burden, except that unlike these beasts human slaves recognize that they need to be ruled. The trouble with this theory, as Aristotle quite explicitly states, is that the right kind of souls and bodies do not always go together! So, one could have the soul of a slave and the body of a freeman, and vice versa! Nonetheless, apparently because there are some in whom the body and soul are appropriate to natural slavery, that is a strong body and a weak soul, Aristotle holds that there are people who should naturally be slaves. It also seems that men naturally rule women and that bararians are naturally more servile than Greeks! This seems like an odd, indeed arbitrary, way for the virtues of the soul to be distributed! Las Casas deals with a similar problem in regard to the native peoples of the Americas.
One interesting feature of Aristotle's discussion which does not clearly come out in the great debate has to do with slavery and war. Aristotle, early in the Politics says:
But that those who take the opposite view [that is, who hold the view that slavery is not natural] have in a certain way right on their side, may be easily seen. For the words slavery and slave are used in two senses. There is a slave or slavery by law as well as by nature. The law of which I speak is a sort of convention-- the law by which whatever is taken in war is supposed to belong to the victors. But this right many jurists impeach, as they would an orator who brought forward an unconstitutional measure: they detest the notion that, because one man has the power of doing violence and is superior in brute strength, another shall be his slave and subject.So, those who hold that slavery is both conventional and legitimate hold the doctrine that all prisoners of war can be legitimately enslaved. If you lose the battle and are captured, that is enough. Aristotle gives reasons for rejecting this view. One is that this means that might makes right. Many people find this doctrine really objectionable. (Plato in The Republic and other dialogues is one of these.) The doctrine that might makes right means that if you have the power, and so win the battle, however unjust your cause, the spoils are legitimately yours. In fact, contrary to most of our intuitions, this view says that wining makes your cause just! Saint Augustine held a view like this conventional view, but he had an answer to Aristotle's objection. Since God decided who would win the battle, victory in battle amounts to a divine decision! To be captured in battle and enslaved is a divine punishment for sin! This connection between war and slavery is of some interest in the study of the period of the conquest of the Americas. For at this time Europeans were beginning to develop what has come to be know as just war theory. This theory holds that their are criteria for determining whether a war is just. So, you can lose but we can still recognize that your cause is just. Or you can win and we can still recognize that your cause is unjust. Courtney Campbell's essay "Dirt, Greed and Blood: Just War and the Colonization of the New World" explores the beginnings of this tradition in the Spanish writer Francisco de Vitoria. A later and important contributor to just war theory during the period we are studying was the Dutch Jurist Hugo Grotius.
This discussion of war and slavery in Aristotle will turn out to be quite interesting when we come to explore John Locke's theory of slavery in The Second Treatise of Civil Government Locke does not believe in natural slaves or in the conventional view that all prisoners of war can be legitimately enslaved. He is a just war theorist who explicitly rejects the doctrine that might makes right.