Aristotle gets a lot of flack for defending slavery. It’s not bad enough that he accepted it, like so many Greek thinkers before him; he went to the trouble of arguing for it. Worse still, his argument is, by almost universal scholarly consensus, pretty bad. The gist of the argument is that some human beings are so rationally deficient that they cannot lead autonomous lives and therefore need to be ruled by others in order to keep out of trouble, or at least in order to live decently; slavery is actually beneficial for them, and they’re better off being slaves than being left to their own devices.

The chief problem with this argument is that it infers not that people who are unable to lead autonomous lives ought to be subject to the authority of others, but that they ought to be slaves. The enormous logical — or illogical, rather — leap here is not shortened by any assumptions on Aristotle’s part that slavery, when properly done, is a benign or benevolent institution. On the contrary, while he insists that justified slavery must be beneficial to the people enslaved, he also insists that the master-slave relationship is, in all instances, an exploitative one driven entirely by the self-interest of the masters. Though people who are “slaves by nature” benefit from being enslaved, masters do not aim at the benefit of their slaves independently of their own. When you rule another person as a slave you regard her in pretty much the same way you regard your hands or your eyes or your car — except, of course, that slaves are easier to replace than body parts. While Aristotle’s defense of slavery therefore has resources to criticize certain especially egregious forms of abuse and mistreatment by masters of their slaves, those criticisms all ultimately take the same form as your doctor’s criticisms of your failure to take proper care of your hands or your auto mechanic’s criticisms of your failure to take proper care of your car (though I think I’ve met some auto mechanics who care more about cars than Aristotle does about slaves). So there’s no getting around the fact that Aristotle argues fallaciously in defense of an exploitative and inhumane social relation. It doesn’t help his case that he seems to be inconsistent about it, either.

As I said, Aristotle gets a lot of flack for this. Those who do not appreciate his other work tend to dismiss him as a reactionary ideologue. Those who do appreciate his other work tend to adopt one of several strategies: ignore the slavery stuff, avoid the slavery stuff, re-interpret the slavery stuff either as a subtle critique or as a defense of something like humane penal rehabilitation, defend the slavery stuff as an honest mistake, or — just occasionally — defend the slavery stuff. I’m not interested in doing any of that here. I think it’s a not-very-honest mistake, but that’s not what strikes me most about it. I’m more struck by how rare defenses of slavery in Greek and Roman antiquity were. But I’m most struck by how rare critiques of it were. Aristotle gives us the closest thing we get to a systematic theoretical justification of slavery. But he also gives us the closest thing we get to a systematical theoretical critique of it for about 700 years.

No extant text before Aristotle critiques slavery as such. We know that somebody attacked it, though, because Aristotle is responding to them when he defends it in the first book of the Politics. He doesn’t name the critics; he just refers to them as “those who assert the opposite” of his thesis. The grounds of their opposition to slavery aren’t fully clear from Aristotle’s report, but the thought seems to have been that slavery is inherently unjust because it is based solely on force: they challenge the convention of enslaving people conquered in war “on the grounds that it is a terrible thing if what yields to force is to be enslaved and ruled by what is able to apply force and is superior in power” (Politics I.6 1255a10, trans. Carnes Lord). Many of us are likely to be sympathetic to this sort of appeal, but Aristotle is right to reject the argument, at least if it’s that simple. For the reasoning seems to be that whatever is based on force is unjust, and since slavery is based on force, it’s therefore unjust. Without some carefully qualified elaboration of what it is to be based on force, however, the fundamental premise is wholly implausible. From the fact that I need to be forced or coerced to do something, it doesn’t follow that it is unjust to force or coerce me to do it; if it did, most parenting, imprisonment, and punishment would be unjust, as would many laws. Libertarian and anarchist proponents of the so-called Non-Aggression Principle might be quick to embrace that conclusion, but even they have to admit that formulating a version of the NAP adequate to their own ideological agenda is no mean feat; that many people intuitively regard their agenda as absurd should be sufficient to show that the principle needs defense and can’t simply be trotted out for a quick and decisive victory. If this is the best that ancient Greek critics of slavery had to offer, then Aristotle was right to dismiss them.

To an extent, though, he agrees with them: “that those who assert the opposite are in a certain manner correct, however, is not difficult to see” (I.6 1255a3). As Aristotle sees it, superior force is never sufficient to justify slavery, and so the critics are right to reject the standard Greek convention whereby the victors in war could enslave their defeated opponents. Though he makes rather less of it than most of us today would expect, Aristotle does in fact think that much conventional slavery in his day is unjust, because the people enslaved are not “slaves by nature,” lacking the rational capacity to live dignified lives as free people; they’re just the losers of a military conflict, or the wives or children or descendants of those losers. So while Aristotle dismisses his opponents’ categorical rejection of slavery as unjust, his recognition that some slavery is unjust is clear as day. Furthermore, his reason for regarding it as unjust is at least as good as any reason your average Jane or Joe on the street today could muster: the people enslaved are human beings with the rational capacity to live dignified lives as free people, and therefore are harmed by being enslaved, because slavery reduces them to tools that other people use to pursue their own self-interest instead of allowing them to cultivate their rational capacities as free people. That Aristotle thought that any human beings would not be mistreated by being reduced to tools for other people’s use is bad enough; but he didn’t suppose that no human beings would, or that whether or not they would is irrelevant to the justice of slavery, or that simply overpowering your enemies — even in a just war — gives you license to enslave them (as Locke thought, Second Treatise ch. 4).

For all that, though, Aristotle shows no apparent interest in rectifying this situation or even in determining how much slavery in his day is merely conventional rather than “natural.” Though his own views provide the theoretical material to support rather wide-ranging reforms of Greek slavery, there is no evidence that he or any of his later followers so much as suggested such reforms. So too, it’s perhaps worth noting that the opponents of slavery that Aristotle reports do not seem to have proposed abolishing it; all we’re told is that they regard it as unjust, as a “terrible thing.” We might naturally infer that some suggestion of abolition was an upshot of their view, but if so it made no mark in the historical record. Such silence does not give us especially good grounds for any positive conclusions, but in general the ancient Greeks seem to have been ready to acknowledge that slavery was awful for slaves, and yet to accept it. As Bernard Williams put it:

Slavery, in most people’s eyes, was not just, but necessary. Because it was necessary it was not, as an institution, seen as unjust either; to say that it was unjust would imply that ideally, at least, it should cease to exist, and few, if any, could see how that might be. If an institution was not seen as either just or unjust, there was not much to be said about its justice, and indeed it has often been noticed that in extant Greek literature there are very few discussions at all of the justice of slavery. – Shame and Necessity, 117.

The Greeks more or less accepted that slavery in some form or other was a necessary institution in civilized life. So while many recognized that being a slave was often or usually a bad thing to be, the few thinkers who seriously entertained the thought that slavery was unjust did not seriously entertain the thought that it might be abolished.

The same is true in the Roman world, where the harshest extant critic of slavery, Seneca the Younger, stopped far short of condemning slavery as such. Here he is on the pervasive mistreatment of slaves by Roman elites:

I’m glad to hear, from those people who’ve been visiting you, that you live on friendly terms with your slaves. That’s just what one expects of an enlightened, cultivated person like yourself. ‘They’re slaves,’ people say. No. They’re human beings. ‘They’re slaves!’ But they share the same roof as ourselves. ‘They’re slaves!’ No, they’re friends, humble friends. ‘They’re slaves!’ Strictly speaking they’re our fellow-slaves, if you once reflect that fortune has as much power over us as over them…

How about reflecting that the person you call your slave traces his origin back to the same stock as yourself, has the same good sky above him, breathes as you do, lives as you do, dies as you do? It’s as easy for you to see in him a free-born man as for him to see a slave in you…many a man of the most distinguished ancestry, who was doing his military service as the first step on the road to a seat in the Senate, was brought low by fortune, condemned by her to look after a steading, for example, or a flock of sheep. Now think contemptuously of these people’s lot in life, in whose very place, for all your contempt, you could suddenly find yourself.

I don’t want to involve myself in an endless topic of debate by discussing the treatment of slaves, towards whom we Romans are exceptionally arrogant, harsh, and insulting. But the essence of the advice I’d like to give is this: treat your inferiors in the way in which you would like to be treated by your superiors. And whenever it strikes you how much power you have over your slave, let it also strike you that your own master has just as much power over you. ‘I haven’t got a master,’ you say. You’re young yet; there’s always the chance you’ll have one. Have you forgotten the age at which Hecuba became a slave, or Croesus, or the mother of Darius, or Plato, or Diogenes? Be kind and courteous in your dealings with a slave; bring him into your discussions and conversations and your company generally…

‘He’s a slave!’ But he may have the spirit of a free man. ‘He’s a slave!’ But is that really to count against him? Show me a man who isn’t a slave! One is a slave to sex, another to money, another to ambition; all are slaves to hope or fear. I could show you a man who is a slave to his ‘little old woman,’ a millionaire who is the slave of a little girl in domestic service. I could show you some highly aristocratic young men who are utter slaves to stage artistes. And there’s no state of slavery more disgraceful than one which is self-imposed. So you needn’t be deterred by the snobbish people I’ve been talking about from showing good humor towards your slaves instead of adopting an attitude of arrogant superiority towards them. Have them respect you rather than fear you.

– Epistulae Morales ad Lucilium 47 (trans. Robin Campbell, slightly modified)

Unlike Aristotle, Seneca does not try to justify slavery on the grounds that some people’s impaired rationality makes them fit for enslavement. On the contrary, he insists that masters and slaves share a common humanity, which for Seneca is fundamentally a matter of being a rational agent. But our common humanity also makes us equally subject to chance and misfortune, which can make slaves of anyone regardless of their prior social standing or their personal virtues. Seneca’s emphatic refrain is that slaves are human beings and that masters ought to treat them with the respect and benevolence due to all human beings. Masters should make their slaves friends and companions, and should always treat them in ways that they themselves would want to be treated by their superiors. In a world where no difference in power or status was greater than that between master and slave, Seneca repeatedly exhorts masters to focus on what they share with their slaves, not what differentiates them. It is not for nothing that Seneca has often been celebrated for his humanity.

Yet not once in the letter — which includes some detailed descriptions of the degrading treatment to which wealthy Romans often subjected their slaves — does Seneca’s injunction to masters to recognize and respect their slaves’ humanity, to treat them as they themselves would want to be treated, extend to freeing them from slavery, much less to abolishing slavery altogether. Roman slaves were frequently freed by their masters, so that option isn’t at all off the table for Seneca. But it seems not to occur to him that freeing one’s slaves would be the only way to treat them respectfully and humanely, let alone that slavery is categorically unjust.

Seneca’s treatment of slavery appears to indulge in what Mary Margaret McCabe, in her Plato on Punishment, calls begging the institution: assuming that an existing institution (for McCabe, legal punishment; here, slavery) is necessary and setting out to justify it rather than putting the institution into question in the first place. Plato famously argued that just punishment needs to be reformative, improving the person punished. Whatever one thinks of that proposal, Plato has been thought to be guilty of simply assuming that punishments of roughly the sort characteristic of 4th century Greek law could be reformative, a much stronger and less plausible assumption than the supposition that punishment of some kind is necessary in social life. Certainly his detailed catalogue of punishments in the Laws does not depart dramatically from ordinary Greek practice and does not, for the most part, seem likely to produce genuine moral reform. Similarly, Seneca proposes that the master-slave relationship should be a kind of friendship, and seems simply to assume that it is possible for people to be genuine friends, treating one another with benevolence and respect, within the confines of a master-slave relationship.

It can be hard for us today to see how anyone as intelligent as Plato could think that harsh physical punishments could morally improve people, or how someone as humane as Seneca could think that benevolence and respect are compatible with owning somebody. But the comparison between Seneca and Plato is instructive, because many of us today continue to regard legal punishment, unlike slavery, as a social necessity. It is, at least, very hard to take seriously the idea that legal punishment is going away any time soon, or that it would be a good thing if it did. We might, of course, take that as a reason to focus on reform, but in fact most Americans do not care very much about prison reform, or think very much about what kind of punishment is justified and why. Those who do think about it in a sustained and focused way — philosophers, political theorists, sociologists, criminologists, lawyers, etc. — tend to come away thinking that our criminal justice system is severely messed up, and to propose various sorts of reforms, most of which seem, to my non-expert eye, to be completely ineffective. But while we can at least hope that theorists of punishment today avoid the mistake of which Plato has been accused, assuming that the institution as it is just happens to be largely consistent with their favored theoretical justifications, few of us can imagine any radically different but realistic alternative, and very few people seriously entertain the idea of abolishing punishment.

Of course, there might be a very important disanalogy here: slavery isn’t a social necessity, and it isn’t just in any circumstances, whereas punishment is a social necessity and at least can be just. I don’t mean to deny this or to suggest that legal punishment is fundamentally unjust. I do mean to say that to the ancient Greeks and Romans, slavery looked every bit as necessary as legal punishment does to us, and that this is why the only serious critics of it in antiquity stopped far short of proposing to abolish it or even of regarding it as inherently unjust.

Indeed, the only figure in Greco-Roman antiquity who is usually thought of as condemning slavery as such and even endorsing its abolishment is the 4th century A.D. Christian bishop and theologian Gregory of Nyssa. In the fourth of his Homilies on Ecclesiastes, he writes:

‘I got me slave-girls and slaves.’ What do you mean? You condemn man to slavery, when his nature is free and possesses free will, and you legislate in competition with God, overturning his law for the human species. The one made on the specific terms that he should be the owner of the earth, and appointed to government by the Creator — him you bring under the yoke of slavery, as though defying and fighting against the divine decree.

You have forgotten the limits of your authority, and that your rule is confined to control over things without reason. For it says Let them rule over winged creatures and fishes and four-footed things and creeping things (Gen, 1,26). Why do you go beyond what is subject to you and raise yourself up against the very species which is free, counting your own kind on a level with four-footed things and even footless things? You have subjected all things to man, declares the word through the prophecy, and in the text it lists the things subject, cattle and oxen and sheep (Ps 8,7-8). Surely human beings have not been produced from your cattle? Surely cows have not conceived human stock? Irrational beasts are the only slaves of mankind. But to you these things are of small account. Raising Fodder for the cattle, and green plants for the slaves of men, it says (Ps104/103,14). But by dividing the human species in two with ‘slavery’ and ‘ownership’ you have caused it to be enslaved to itself, and to be the owner of itself.

‘I got me slave-girls and slaves.’ For what price, tell me? What did you find in existence worth as much as this human nature? What price did you put on rationality? How many obols did you reckon the equivalent of the likeness of God? How many staters did you get for selling that being shaped by God? God said, Let us make man in our own image and likeness. If he is in the likeness of God, and rules the whole earth, and has been granted authority over everything on earth from God, who is his buyer, tell me? Who is his seller? To God alone belongs this power; or, rather, not even to God himself. For his gracious gifts, it says, are irrevocable. God would not therefore reduce the human race to slavery, since he himself, when we had been enslaved to sin, spontaneously recalled us to freedom. But if God does not enslave what is free, who is he that sets his own power above God’s? (trans. Stuart George Hall)

That looks like a pretty categorical rejection of slavery as inherently unjust and sinful, and so it is usually read. Yet even here there is scholarly dispute about whether Gregory endorses the abolition of slavery as an institution. One might think that the very possibility of such a debate tells in favor of those who deny that Gregory was an abolitionist. Famously, mainstream Christian moral teaching did not standardly condemn slavery until relatively recently in its long history, so even if Gregory was seriously endorsing abolition, his view was decidedly a minority opinion. In any case, it isn’t hard to see how some readers see the sharp denunciation of slavery as consistent with acceptance of the institution: slavery is a mark of a sinful world, but that’s just how the world is, for now. Some might feel inclined to diagnose Gregory’s failure to issue an unequivocal call for abolition as a symptom of a pervasive failure of Christianity and other sorts of other-worldly religions: it’s a fallen world, but there’s nothing we can do about that for now, so try to be good in your personal life but forget about radical social change. I don’t think that sort of diagnosis is accurate if applied to Christianity as a whole, but even if Gregory was so afflicted, his homily is more remarkable for what it says than for what it doesn’t. Even if he fails to take his critique of slavery all the way to abolition, he gives us the ancient Greco-Roman world’s most total and uncompromising condemnation of slavery as such. Though it’s a thoroughly theological condemnation, it isn’t too hard to appreciate it from a secular point of view (at least one broadly sympathetic to the tradition of naturalist moral realism that begins with Plato and Aristotle). Next to Gregory’s repudiation of the institution, Seneca’s supposed humane sensitivity comes to look like nothing so much as moral idiocy.

But it wasn’t moral idiocy. It wasn’t even lack of imagination. It was an inability to imagine realistic alternatives. I often think that our now near-unanimous rejection of slavery is a good illustration of how moral thinking is empirical, in large part a matter of experience and not simply a matter of deducing conclusions from abstract, self-evident principles; we reject slavery now as a matter of course not because its injustice is obvious to all rational beings who manage to think straight, but because we are the beneficiaries of many generations of painful experience and reflection. Usually I think this is a reason not to be so hard on ancient Greeks and Romans who took slavery for granted and failed to challenge it. But probably we ought also to learn from their failures not to congratulate ourselves so readily. Most of us probably wouldn’t have done any better had we been Greeks or Romans. Worse, many of us might be making the same sort of mistake now about a different set of social and political realities.