Aristotle's Defense of Natural Slavery

Aristotle's defense of slavery in Politics 1.2-7 is grounded in the belief that slavery is natural and necessary for society to function effectively. He differentiates between natural slavery (some individuals are by nature suited to be ruled) and conventional slavery, which rests on custom like the rule that whatever is taken in war belongs to the victors (1.6, 1255a4-7). His argument however relies on some basic assumptions about the nature of justice, social order and rationality, which I think deserve some close examination. The defense starts in the household, where the first unions are between "those who cannot exist without each other," male and female so that the race can continue and "natural ruler and subject, that both may be preserved" (Pol. 1.2, 1252a26-31). He explains the second pair: "For that which can foresee by the exercise of mind is by nature intended to be lord and master, and that which can with its body give effect to such foresight is a subject, and by nature a slave" (1252a31-33). Households combine into villages and villages into the city (1252b27-31), so for Aristotle the naturalness of slavery originates in the household and not at the level of politics, and the city is this structure scaled up. Here he draws a clear difference between those who lack independent rationality (natural slaves) and those who are capable of rational deliberation and foresight (natural masters), but natural slaves are not without reason altogether. A slave by nature "participates in rational principle enough to apprehend, but not to have, such a principle" (1.5, 1254b22-23) and later Aristotle says that "the slave has no deliberative faculty at all," while the child has one "but it is immature" (1.13, 1260a12-14). So the full extent that the natural slave falls short of is deliberation, working out for himself what to do and why. He can understand an instruction but he can't be the source of it, and this is what bears on ownership. Since natural slaves can't direct their lives towards reasoned ends someone else has to deliberate for them, so they are suited to be owned in the same way a tool belongs to its user. This is why a slave is "a living possession" (1.4, 1253b32) and why whoever is "by nature not his own but another's man, is by nature a slave" (1254a14-15).

But why is this arrangement natural? Book 1.2 asserts it and 1.5 gives the reason. In anything "made up of parts" Aristotle says that "a distinction between the ruling and the subject element" appears, and this duality "originates in the constitution of the universe" (1254a28-32). He finds the same pattern in soul and body and in men and tame animals, and concludes that where people differ as much as soul from body "the lower sort are by nature slaves" (1254a34-b19). This means soul and body are not an analogy for master and slave since both are instances of one structure in which reason governs what lacks it, which is why he says that "the soul rules the body with a despotical rule" (1254b4-5), the kind of rule a master has over a slave. Aristotle isn't justifying a human institution by pointing to something in nature that it resembles (the way a social Darwinist might). Instead he is claiming that human society is itself a manifestation of natural order and that the social arrangement answers to a natural fact about humans, which is that some can deliberate and some cannot. Furthermore slavery serves the city since those "in a position which places them above toil have stewards who attend to their households while they occupy themselves with philosophy or with politics" (1.7, 1255b35-37), and in Book 7 he says citizens of the best city shouldn't farm because leisure is needed for developing virtue and for political activity (7.9, 1328b39-1329a2). I think this claim is about free time and not capacity, which is different from the claim that natural slaves couldn't use leisure well even if they had it, and Aristotle holds both.

Despite firmly defending natural slavery Aristotle acknowledges that not all forms of slavery are natural or just. He grants that the opponents of slavery "have in a certain way right on their side" (1.6, 1255a3-4) because some slavery only exists by the convention of war, and "no one would ever say he is a slave who is unworthy to be a slave. Were this the case, men of the highest rank would be slaves and the children of slaves if they or their parents chance to have been taken captive and sold" (1255a25-28). This challenges the Greek belief that military superiority is an automatic justification for enslavement and suggests that this type of enslavement (by military force alone) lacks moral legitimacy. This doesn't mean that natural slaves will be content with their condition though. Where the relation is natural master and slave "are friends and have a common interest" (1255b12-14), but that is a claim about what is good for the slave and not about how he feels, so his nature suits him to be ruled whether he recognises it or not. This raises an important question: if a just system of slavery depends on correctly identifying natural slaves, how can we reliably achieve this in practice? Aristotle doesn't offer a method and instead treats ethnicity as settled. He endorses the poets' line "It is meet that Hellenes should rule over barbarians," taking them to mean that "the barbarian and the slave were by nature one" (1.2, 1252b5-9), and he says that when Greeks "confine the term to barbarians" they "really mean the natural slave" (1.6, 1255a28-31). I don't see any sign that he offers this as an estimate or a useful fiction since he states it as a fact, and to me this causes conflict in his argument. If slavery is entirely based on nature then it shouldn't depend on ethnic or cultural distinctions, but Aristotle blurs the line between biology and culture by leaning on a pretty broad cultural generalisation that undermines the objectivity of his own criteria. Whilst his justification for slavery is systematic, it relies on some decisive assumptions about rationality, our nature and justice that I don't think hold up when we examine them more closely.

Aristotle grants that slaves "are men and share in rational principle" (Pol. 1.13, 1259b27-28), and On the Soul describes what having a share like this means. The soul is "the first grade of actuality" of a living body, first in the way that knowledge someone has comes before knowledge they are using (On the Soul 2.1, 412a22-28). In 2.5 he separates three senses of "knower," someone who counts as one because "his kind or matter is such and such," someone who has learned grammar and can use it when they want and someone actually using it, and the first only becomes the second through "repeated transitions from one state to its opposite under instruction" (2.5, 417a21-b2). On the Soul doesn't rank people by levels of reason (that hierarchy is in the Politics) but together the two texts make human reason a potentiality that develops through instruction, so enslaving someone for their current capacity treats a temporary state as a permanent one. Aristotle accepts this for children, who don't have mature deliberation but aren't natural slaves because they will grow into it. If that is the case then why should those who are slower in developing their rationality be restricted to a role of slavery? He might reply that someone has to do the necessary labour, so no injustice is done if it falls to people who could have done otherwise. But I think slavery is different from any other job because it is the one role that removes the conditions under which reason develops. A slave needs "only so much virtue as will prevent him from failing in his duty" (Pol. 1.13, 1260a33-36), so his education is set by his use to his owner and not by what he could become, and Aristotle even says slaves "stand even more in need of admonition than children" (1260b5-7), which concedes that they respond to reasons. The injustice in my opinion is in closing off a person's potential for virtue based on assumptions about their fixed status, when Aristotle's own account of the soul says that potential is realised through cultivation. Even if we grant his claim that some individuals are naturally suited to servitude, there still remains the practical issue of how we can reliably determine what a natural slave is, and reliability matters here more than in almost any other social judgment. A mistake costs the person everything since a capable person who is misjudged doesn't just get the wrong job but becomes property. The mistake also confirms itself because the enslaved person is denied the instruction through which his capacity would show. And Aristotle admits that the trait can't be seen, since nature "would like" to give free men and slaves different bodies "but the opposite often happens," and "the beauty of the soul is not seen" (Pol. 1.5, 1254b27-1255a1). Just distribution has to be "according to merit" (NE 5.3, 1131a24-26), so if merit can't be seen then rational people will be enslaved, which Aristotle would have to call unjust.

While these objections challenge key aspects of his argument, he might argue that his theory of natural hierarchy stays intact even if rationality exists in all humans as a potentiality. He may respond by differentiating between the possession of rationality and its actualisation, and On the Soul gives him the terms for this. Every human is a knower in the first sense, but natural slaves would be those whose potential for deliberation never reaches the second, which fits the division in Politics 1.5 between those who have reason, those who only apprehend it and animals, which "cannot even apprehend a principle" (1254b23-24). For example a person born with the capacity for music does not immediately become a great musician. Discipline and training are required to actualise that potential, so just because all humans have rational souls doesn't mean that they are equally capable of governing themselves. The child is a musician who hasn't trained yet but the natural slave would be someone who no amount of training will turn into one. In response to the problem of identifying natural slaves, he may appeal to the broader necessity of a structured hierarchy. A family requires a father to govern and children to obey and a city requires a labouring class and a ruling class to function effectively, so while misapplications of slavery may occur, they do not negate the necessity of a naturally subordinate class in maintaining political order. Aristotle may also argue that some people will always need external governance, so rule is justified not on individual rights but on the well-being of the individuals being ruled.

Even if this response gives Aristotle internal consistency it doesn't resolve the ethical concerns raised by his theory. The well-being defense only works where identification is correct, which is exactly what is in doubt, and for anyone else slavery rests "merely on law and force" (Pol. 1.6, 1255b14-15). The Ethics admits that although no one can be friends with a slave as a slave, "qua man one can; for there seems to be some justice between any man and any other who can share in a system of law or be a party to an agreement" (NE 8.11, 1161b5-7). I think this is close to a right without the word, something owed to a person because of what he is and not because of his use to a household. If a slave is owed justice as a man then owning him needs more than an argument that it is good for him. It needs confidence that he can't run his own life, which Aristotle has admitted he can't have. Rule over children is also for the good of the ruled, but it aims at their becoming free, whereas slavery is permanent.

In conclusion, Aristotle presents a relatively coherent but deeply problematic justification for slavery, because it depends on two things he can't secure, that the natural slave's deficiency is permanent and that it can be detected. If just distribution follows merit then a system that will enslave rational people through misidentification fails by his own standard and not just by ours. The step from needing someone to do the work to owning a particular person is the one his argument never earns. I wonder whether he could have kept his theory at all if he had taken his own point seriously, that the soul which would justify it cannot be seen.

Works cited

• Aristotle, Politics, trans. Benjamin Jowett; On the Soul, trans. J. A. Smith; Nicomachean Ethics, trans. W. D. Ross.