2.2.1 Legitimising Slavery Before the Atlantic Slave Trade: Between Aristotle and the Romans

2.2.1.1 Greek Thinking on Slavery: Balancing Physis and Nomos

The first stop within our intellectual tour of European slavery ought to lie in Classical Greece. The Greek tradition is important in two ways.

Theorising on slavery only began long after the institution itself was established. This can be aptly seen in the Homeric world, where slavery was accepted as fact, without any underlying theory. However, in the ensuing centuries, the Greek view of slavery would change by two parallel evolutions: Hellenic nationalism and a disdain for certain banausic occupations.¹⁶ This sense of Hellenic unity increased by a combination of factors: leagues, pilgrimages and festivals which gave the Greeks some sense of cultural unity as opposed to â€?barbarian’ outsiders, the Greek wars against the Persians in which they encountered the absolutist nature of the Persian monarchy, etc. This evolution gave rise to feelings of superiority, which meant that Greeks saw outsiders as destined by nature to become slaves. The disdain for banausic occupations grew as well during this time, visible in the fact that Greeks believed that some menial occupations were unworthy of being done by freemen.

In the Greek era, we also find the birth of what would later become the ius naturale and the ius gentium. The Greeks did not use these exact words. Rather, they held that some rules were universal throughout the human race and derived from nature (physis), whilst other rules were specific to one state or a group of states (nomos). Nature could serve as a model for human conduct, and a source for legal norms.¹⁷ When it comes to slavery, this meant that the institution, present amongst the Greeks, could be legitimised in two ways.¹⁸ Some held that slavery belonged to those universal rules of mankind, and that some men were naturally fit to become slaves.

One of the proponents of the theory of natural slavery was Plato, who discussed slavery within his Republic and Laws (although in fact, Plato’s ideas on slavery were broadly based on the contemporary Attic law of slavery).²¹ However, instead of giving a concise statement, the views of Plato on this subject are spread around these two works. The criterion that Plato used to decide who was a natural slave was quite abstract, a natural slave being a person with “a deficient state of mind’’.²² At the same time, Plato’s views can easily be fitted within the theory of Hellenic nationalism, as he denounced the practise of enslaving fellow Greeks but did not have the same qualms about “barbarians”.²³

Though Plato wrote on slavery, the most influential views were undoubtedly those of Aristotle.²⁴ His views on slavery are part of the Politics, where, when starting his discussion on the state, he first looks at the elements of which the state is composed. At the smallest level, Aristotle places the household, where he believes three relationships are important to discuss: slave-master, husband-wife and father-children.²⁵

Aristotle begins by setting out the point of contention: that according to some, slavery is contrary to natural law and that it is only convention (nomos) that created the difference between a freeman and a slave. This convention is based on force, and according to the proponents of this theory, therefore unjust.²⁶ This “human convention” Aristotle talks about, is a reference to the laws of war, with prisoners of the vanquished often being kept in slavery.

The first point in Aristotle’s theory is to show that his opponents are wrong: according to him, natural slaves do exist. To be such a natural slave, two criteria have to be fulfilled: natural slaves are human beings “not belonging to themselves but to another person” and are people participating in reason to understand it but not to possess it themselves.²⁷ Aristotle admits that, practically, it can be difficult to distinguish a natural slave on the basis of this mental criterion, acknowledging that beauty of the soul is not as easy to see as beauty of the body. And even though he adds that surely, the intention of nature was to make a distinction between the bodies of freemen and slaves so as to make this distinction easier, he admits that it is possible for a natural slave to have the body of a freeman.

The second part of the theory is a typical case of Aristotelian reasoning: Aristotle admits that there is some truth in the statement of his opponents, whilst maintaining in his conclusion that everyone does actually agree with him.²⁸ It will be recalled that some of the Sophists judged that slavery only existed by human convention through the laws of war, but not on the basis of natural law. According to Aristotle, there are two ways to possibly justify this idea: first, by admitting that might makes right, or second, by conceding that whatever is legal must also be right. When discussing the first justification, Aristotle notes that some say that only virtue can make a right, whereas others would say that might is a valid claim to a right. He believes both theories overlap, because the latter see “might” as some form of virtue. This means that both parties agree that someone with moral superiority has a right to rule.²⁹ Next, Aristotle denounces the second theory as inconsistent and hypocritical: he does not believe that it is a general principle of law that anyone conquered in a war is rightly enslaved. On the one hand, no one would agree that it is right to enslave Greek noblemen in a war.

2.2.1.2 Slavery in Roman Law: Institution of the Ius Gentium

If there has ever been an example of what is called a “slave society”, Ancient Rome immediately comes to mind. Spurred by rapid conquest at the end of the Republican period, the trickle of slaves already present in Rome for centuries quickly grew to a steady flow of slaves, amounting to a conservative estimate of 2.000.000 slaves at the end of the Republic in Italy (about 35% of the Italian population).³¹ Generally, the number sharply declined towards the end of the Roman Era.³²

The Roman slave himself was seen as some form of hybrid creature: both a thing (res) and a human being (persona). On the one hand, given that the slave was subject to ownership (dominium), he could be judged as a res (more specifically, he fell within the economically more important category of the res mancipi). On the other hand, the slave’s personhood was not denied. Although in modern terms, the term persona might imply as a necessity the capacity for rights, for the Romans this term only meant “human being”.³³ From a legal point of view, this hybrid status did not entail some inherent consistency, as it was perfectly possible to think of a human being as property, more specifically, thinking property.³⁴

There were various means through which one could become a slave in the Roman system.

Given the longevity of slavery within the Roman world, the law was never static, and two evolutions are relevant to the rest of our story:

First, the character of Roman slave law fundamentally changed throughout the centuries. In the Republic, there were little to none legal limitations on the power of the dominus towards his slave. This did not mean that slaves were necessarily treated cruelly: the number of slaves was still quite small, slaves’ relationships with masters were often close, and the censor could provide a check on cruel masters.³⁸ However, starting from the Imperial period, legislation was devised to prevent abuse of dominial power by the master, meaning that the slave progressively acquired more rights, a process that was even noticed by the great Roman jurist Gaius (130–180).³⁹

Second, between the fourth-sixth centuries, a distinct group called the coloni appeared in the classical texts. Originally free contractual tenants, the word came to be applied to a category of people that had been tied to their land as a result of administrative pressure and fiscal reasons, creating a group that would be reminiscent of the serfs of the later medieval period.⁴⁰ Although nominally free, the increasing burdens imposed on them made Justinian doubt whether their actually still was a difference between the colonus and the servus.⁴¹

As concerns the meta-level, the question of the legality of slavery as an institution, we have to turn back to natural law and ius gentium.

Although slavery had been discussed before by Cicero, Seneca and others, the continuing legacy of Roman slavery lay within the transmission of Justinian’s sixth century Corpis Iuris Civilis. In the Digest, Gaius pronounced that the great division in the law of persons was that all men were either free or slaves, and this was followed by Florentinus’ definition of what slavery exactly was: slavery is an institution of the ius gentium, whereby someone is against nature made subject to the ownership of another (servitus est constitutio iuris gentium, qua quis dominio alieno contra naturam subicitur).⁴⁴ No longer was slavery thus grounded on the ius naturale: its basis ought to be found in the ius gentium. According to Watson, this change in legitimacy might have created some uneasiness, which is why another text by Florentinus was added next to his definition of slavery. He clarified that slaves are so called, because generals have a custom of selling their prisoners and thereby preserving rather than killing them.⁴⁵ The result is that slavery is justified by clarifying that the slave has received a benefit: instead of being killed, his life is spared.

2.2.1.3 Medieval Europe: Continuity, Sin, and the Return of Aristotelian Thinking

Catholic Doctrine and Slavery: Reconciling Equality and Slavery Through Sin

The collapse of the Western Roman Empire ushered in a period of intellectual stagnation in Europe. Mainly, it was the Catholic Church that succeeded in ensuring a measure of intellectual continuity with the previous period.⁴⁶

Christian thinking on slavery started with St. Paul (ca. 5–64/67), who made a twofold distinction that would essentially remain in sway well until the twentieth century in catholic doctrine.⁴⁷ On the one hand, it was held that, fundamentally, all people are equal in Christ. This principle, namely that all human beings are equal as children of God, was affirmed by later theologians and canon lawyers at every moment.⁴⁸ On the other hand, despite this acknowledgement, slavery was condoned by St. Paul. However, he stressed the importance of fairness in the relationship between master and slave, and encouraged manumissions of slaves.⁴⁹ In the Council of Gangra of 340, this permission of slavery was mentioned in a decree, which subsequently became part of the Decretum Gratiani.⁵⁰

The Patristic Fathers (first-seventh century) agreed with this approach, but adjusted their terminology more to the Roman way of thinking. Augustine (354–430) knew about the Roman ius naturale, although in his vision, it was identified as the law of God, and he did not pursue an abstract theory on the issue.⁵¹ In Augustine’s views, mankind did not owe the institution of slavery due to its original nature, but because of its own sin. After the fall of man, sin had arisen in this world and, as a result, slavery served as a disciplinary system to adjust the sinful tendencies of mankind.⁵² Other Patristic fathers agreed with the idea that slavery was not part of the natural state of mankind. Isidore of Seville (560–636), for example, placed it squarely in the ius gentium.⁵³ Conceptions of what this ius gentium was, could differ. For Isidore, the ius gentium and the ius naturale were less closely related. The ius gentium was manmade law. The ius naturale was not. Furthermore, the ius gentium was related to activities of states, whereas the ius naturale pertained more to the conduct of individual persons. Some others scholars were inspired by Augustinian thinking and believed in a conception of the ius gentium as a debased form of ius naturale, more suitable to mankind in its fallen state.⁵⁴ But whatever the relationship between the two was, until the twelfth century, canonists broadly agreed that slavery was not to be seen as part of the ius naturale.⁵⁵

Romanists and Coutumiers: Same Beliefs, but Different Unfreedom

Clergymen were not the only ones to discuss the issue of slavery. After the study of Roman law had first gained hold in Bologna and soon after in the wider region, we also find slavery discussed amongst the works of the Romanists. As slavery remained common in Southern Europe, it made sense that these lawyers took note of how the Corpis Iuris Civilis dealt with slavery. And they squarely fell in line with its treatment of slavery. Great jurists such as Bulgarus (ca. 1100–1167), Placentinus (1130–1192) and Hugolinus (d. 1233) simply restated what the Roman jurists said, holding that slavery was lawful, not according to the ius naturale, but according to the ius gentium.⁵⁶

At the same time, there was a distinction between much of the doctrinal work of the Romanists, and the reality of law as it existed on the ground in the Middle Ages. In the thirteenth century, we also find the first great works on the customary laws of several realms. Most notable are Eike von Repgow’s (c. 1180–1233) Sachsenspiegel in Germany,⁵⁷ Philippe de Beaumanoir’s (1252/1254–1296) Coutumes de Beauvaisis in France and Bracton (c. 1210–1268) in England.⁵⁸ All three of them agree in holding that in the beginning, mankind was free. Unfreedom could thus only exist by convention, not nature. That being said, there is a difference. In contrast to the Romanists, when they talk about unfreedom in their regions, they are talking about serfs, not slaves.⁵⁹ Again, this made much sense, given that, as we will still see, slavery had perished in these countries by the time these works were written.

Thomas Aquinas and His Followers: The Return of Aristotle

The biggest change in legal reasoning on slavery took place in the thirteenth century, when the “rediscovery” of Aristotle’s works gave rise to the school of Scholasticism and its most famous scholar, Thomas Aquinas (1225–1274). With the scholastics, we find yet another conception of the relationship between the ius naturale and the ius gentium. If anything, the Scholastics “rationalised” natural law. As in Antiquity, it was seen as being independent from the will of God, although the Roman vision of a law “common to all animals” was rejected as well. Natural law became external from the human frame, and its content could only be accessed by study and reasoning.⁶⁰ In this tradition, the ius gentium was closely linked to the ius naturale. The ius gentium was still recognised as man-made law, but only in the limited sense that humans had to employ their reason in order to discover what natural law required them to do in certain cases.⁶¹

On slavery, Aquinas endeavoured “to bring together the tradition which he inherited from the Stoics and the Fathers with what he had learned from Aristotle”.⁶² At one point, he maintained that, in the state of innocence, there was no slavery. Two other fragments from his Summa Theologica however, seem to indicate something else. In the first fragment, Aquinas tries to square the circle of his belief in a close connection between ius naturale and ius gentium, St. Isidore’s broader distinction between ius naturale and ius gentium, and Aristotle’s belief in natural slavery. He does this by making the (rather abstract) point of a belief in two kinds of natural law: natural law in the absolute sense and natural law in relation to its consequences. Slavery belonged to the latter category, not being natural in itself, but being natural in the sense that “it is useful for the slave to be controlled by the wiser man, and for the wiser man to be helped by the slave”. In a final fragment, Aquinas seems to build on this belief, noting that slavery does not represent a contradiction, but rather an addition to natural law.⁶³

Whilst Aquinas’ balancing act makes it difficult to come to a confident judgment on his views regarding slavery, one could try to summarise by saying that Aquinas seems to have recognised “two levels of naturalness”. On a first level, slavery was not natural. If one looked at the consequences of slavery in particular cases, it could, however, be seen as natural.⁶⁴

Some of Aristotle’s pupils do not seem to have engaged in such sophistry and went wholesale with the Aristotelian conception. For example, Ptolomy of Lucca (ca. 1236–1327) and Egidius of Colonna (ca. 1243–1316) flatly held that slavery was part of natural law.⁶⁵

2.2.1.4 A Changed Custom: Slavery and European just Wars

One final evolution regarding the legal aspects of slavery in Europe remains to be discussed: the treatment of the defeated in a war on European soil. The Romans used war as a means to legitimise slavery, as they held that the enslaved had actually received a benefit, namely not being killed.⁶⁶

One of the crowning achievements of the Christian Middle Ages was the development of just-war doctrine, which tried to answer the question when armed force could be justified (the state of war was part of the ius gentium).⁶⁷ The doctrine fundamentally needed to explain how it was possible to combine the pacifist views of the New Testament Gospels with situations in which the individual seemed to have to resort to violence. Out of this conundrum, a whole body of law developed during the Middle Ages with a set of intricate rules on when exactly one party could wage a just war on another entity (aptly summarised by the five elements that were discussed by Raymont of Penafort: auctoritas, personae, res, iusta causa and animus).⁶⁸

What concerns us is what just war doctrine had to say about the treatment of those who were defeated in battle: could these people still be enslaved by the victors?

During large parts of history, we do not find much on this question. In a first period (fifth-eighth century), this was mostly due to the fact that enslaving the vanquished in wars was considered too obvious to merit attention.

Following on this, the Romanists of the twelfth century generally did not add much to the old Roman doctrine on enslaving prisoners of war, with at most some exceptions to enslavement that were discussed by Placentinus and Accursius.⁶⁹

Likewise, canon lawyers mostly stayed within the confines of what already been written before. Many Decretists contented themselves with discussing the question whether Saracens could legally take Christians as slaves during the Crusades.⁷⁰ Some Decretalists, however, believed that what happened to property and subjects captured in war merited a longer discussion of what had hitherto been provided by their predecessors. By all accounts, they made interesting treatises on how property rights were affected by warfare, but alas, the same could not be said of their treatment of the personal status of the captured, which was usually rather succinct. Johannes Teutonicus (d. 1245), for example, did acknowledge that only those who fought a just war were entitled to the right of capture, whereas the victims of those who waged unjust wars were not legally enslaved and were encouraged to escape.⁷¹

Likewise, even Thomas Aquinas provided a very unsatisfactory answer to the issue, by noting that only barbarians could be enslaved after being captured in war, a status that was unbefitting for nobles.⁷² Again, this is a mere restatement of the Aristotelian doctrine of natural slavery. Some of Aquinas’ students, such as Ptolomy of Lucca, likewise reiterated the doctrine of Roman law on the enslavement of war captives. Thus, legal reasoning on the subject had virtually gone back to its Roman starting point without much change.⁷³

It is quite interesting then, that there was a remarkable change at the end of the fourteenth century. Consider John of Legnano (1320–1383), whose Treatise Concerning War, Reprisal and the Duel can be regarded as the first important work in Western civilisation that attempted to discuss “international law”.⁷⁴ In one of his questions, Legnano asks whether persons that were captured in a war between two states became slaves. According to him, one had to make a distinction whether the war was between two states which are under the same ruler, or whether this was not so. In the first case, it was held that enslavement could not occur. In the second case, it was held that enslavement was possible, albeit with the exception that did this not apply in wars between Christian states. Why? Because “the customs of modern times, and the practices observed among Christians from an early age” had rendered this practise obsolete.⁷⁵ Such ideas were also confirmed in “popularised versions” of Legnano’s treatise, such as HonorĂ© Bonet’s (ca. 1340–1410) Arbre des batailles and Christine de Pisan’s (ca. 1364–1430) Le livre des faits d’arme et de chevalerie (ca. 1410).⁷⁶

Capturing defeated troops did not disappear all of a sudden, but instead, the Christian states devised complex systems of ransom and hostage-taking, which eventually came in the place of enslaving prisoners of war.⁷⁷ What caused this sudden change is less clear and has not been well studied, though some authors propose a link with the Catholic Church. This matches with Giovanni Da Legnano’s assessment of the disappearance of enslavement in Christian wars. Although the church had an ambiguous position towards enslaving Christians until the end of the Middle Ages, it had prohibited the trading of Christian slaves from the early Middle Ages onwards. When that prohibition was in place, Gillingham argues that over time, it must have made less sense to enslave persons in war in the first place. Likewise, he argues that it is impossible to arrive at a precise chronology, but is convinced enslavement of war prisoners must have slowly ceased to exist within some of the Christian core-countries (e.g. the Frankish state), before this norm slowly extended towards the periphery of Christendom (e.g. the Anglo-Scottish border at the thirteenth century).⁷⁸ Second, adding to Gillingham’s argument, one could also point to the fact that slaves had virtually disappeared in some regions of Europe by the twelfth century due to a mix of economic, political and religious reasons. At this point then, these two arguments help to understand the disappearance of slavery in Christian wars.

In any case, this meant that enslavement in war had completely disappeared amongst Christian nations at the end of the Middle Ages, something that has been identified by one commentator as “the most striking innovation” in the legal conduct of hostilities during the Middle Ages.⁷⁹