In addition to scripture, those arguing for the inherent inferiority of slaves adopted the concept of natural slavery from Aristotle’s Politics and Ethics. Those texts were less popular among Muslim scholars than Plato’s Republic, so Aristotelian natural slavery had relatively little influence on Islamic thought.38 But because Aristotelian texts formed the bedrock of the Christian university curriculum, Christian scholars were more willing to embrace natural slavery.
The Politics was translated into Latin in the thirteenth century, and scholastic commentaries appeared almost immediately.39 The commentators tended to harden Aristotle’s statements on slavery, seeking consistency in a flexible text. One flexible element was the relationship between natural and juridical slavery. In some passages, Aristotle declared that juridical slaves were also slaves by nature, while in other passages, he conceded that natural masters might find themselves juridically enslaved. To address this inconsistency, the commentators tried to identify natural slaves in their own era, but what they found depended on which aspects of Aristotle’s definition they chose to emphasize.40 Those who emphasized rulership concluded that citizens, the ruled, were Aristotle’s natural slaves. Those who emphasized physiognomy concluded that artisans or peasants were natural slaves because they were large and strong. Those who emphasized lack of reason concluded that barbarians were natural slaves. Because Aristotle associated barbarism with Scythians, the inhabitants of the Black Sea, this final answer came closest to the reality of late medieval slavery.
In his Summa theologica, the thirteenth-century theologian Thomas Aquinas famously endeavored to reconcile the truths of scripture and of Aristotle. The result was a powerful argument for the natural inferiority of slaves. Part of Aquinas’ argument was outlined at the beginning of this chapter: he saw the dominion of some people over others as a natural aspect of human society from the moment of creation. However, drawing on Aristotle, he identified two forms of dominion.41 In the civil form, the ruler exercised power over the ruled for the benefit of the ruled. This was the dominion exercised by the free over the free, rulers over citizens, and husbands over wives, and this was the dominion that existed in Eden. In the second, servile form of dominion, the ruler exercised power over the ruled for the ruler’s own benefit. This form of dominion emerged from sin and was thus appropriate to the fallen world. It was exercised by tyrants over subjects and masters over slaves.
Setting aside philosophical debates about freedom and the nature of humanity, both Christians and Muslims recognized slavery in practice as a legitimate institution arising from and defined by human law.42 They agreed that some slaves were born into slave status and that free people could be legally enslaved if they were unbelievers captured in war.43 Penal enslavement and the sale of free people into slavery were forbidden by Islamic law.44 The Justinianic Code permitted parents to sell their children into slavery; canon law also permitted it “in greatest necessity.”45 Selling oneself into slavery was forbidden, but the punishment for doing so was permanent enslavement.46 Both the Justinianic Code and canon law also prescribed enslavement as a punishment for certain crimes.47 In theory, for example, the concubines of priests could be sold into slavery, but in practice, the harshest punishment they suffered was exile.
Slave status involved both legal objectification and legal weakness. In the context of property law, slaves were objects and not persons. They could be bought, sold, gifted, rented, pledged, and otherwise disposed of like any other type of property.48 The injury or death of a slave was considered property damage. Slaves were often grouped with animals in legal texts because both were living property.49 In the context of family and criminal law, slaves were recognized as persons but were legally weak. They could not own property, inherit or bequeath property, conduct business, hold positions of legal authority, testify in court, execute a will, or serve as a legal guardian.50 If slaves were found guilty of a crime, their masters might be held responsible for the associated fines or punishments. Some aspects of slaves’ legal weakness could be mitigated by their masters. For example, Islamic law allowed a master to authorize a slave to conduct business.51 Slaves of both Muslims and Christians could own a small amount of personal property, a peculium, which nominally belonged to their masters but in practice could be used to buy freedom. In certain respects, the legal weakness of slaves was comparable to that of women, minors, and the mentally ill.
Slavery and Religious Difference
Although slavery was legal in the late medieval Mediterranean, there were norms regarding who could enslave whom. Late medieval Mediterranean slavery was intrusive, meaning that slaves were supposed to be outsiders brought into the slaveholding society rather than insiders excluded or degraded from the slave-holding society.52 The main criterion used to distinguish outsiders from insiders with respect to slavery was religion. Adherents of the same religion should not enslave one another, but adherents of different religions could enslave one another.53 The special status granted to certain religious groups included both protection from enslavement and restrictions on slave ownership. Muslim authorities did not allow local Christians and Jews to own Muslim slaves, but they also forbade their enslavement by local Muslims.54 Christian authorities did not allow local Muslims and Jews to own Christian slaves, but they also forbade their enslavement by local Christians, except in cases where enslavement was the judicial punishment for a crime.55 When state protection was withdrawn, as when the Jewish population of Spain was expelled by Ferdinand and Isabella in 1492, these groups became vulnerable to enslavement.56 Apart from protected groups, Christians were allowed to enslave Muslims, Muslims were allowed to enslave Christians, Jews were allowed to enslave Muslims in Christian states and Christians in Muslim states, and everyone was allowed to enslave pagans.
In addition to the expectation that slaves must come from different religious backgrounds than their masters, there was also an expectation that slaves would convert to the religion of their masters and that such conversions did not require manumission.57 On the Islamic side, jurists permitted the forcible conversion of certain types of people, including women, children, and prisoners of war.58 Converting slaves without manumission was thus legally straightforward. On the Christian side, canon law considered forcible conversions invalid because the sacrament of baptism required an intention to convert on the part of the person baptized. Late medieval missionaries, however, argued that masters with pious intentions could baptize enslaved children because they did not yet have the ability to form intentions or make binding vows themselves.59 Still, manumission was not required, because the conversion of a slave was not an act of free will and because slavery was closely associated with sin. As explained by Franco Sacchetti, the son of a free Florentine man and a slave woman, “he who does not believe in the reward of Christ ought not to be free … for the most part they are like oxen to baptize. He does not even agree to become Christian through baptism. One is not held to free him, although he may be Christian, if he does not desire it. I do not say, that if he seems good and has the will to be a good Christian, that you do not do [an act of] mercy by freeing him, just as it would be bad and a sin, having a slave man or woman of guilty condition, as the greater part are, although he might be Christian, to free him.”60 In other words, converted slaves should remain under the paternalistic control of their masters for their own moral good.
The apparent simplicity of slavery based on religious difference was complicated by sectarianism. The Sunni–Shiʿite split within Islam was used to justify enslavement during the Ottoman era but not under the Mamluks.61 More important to late medieval slavery was the Catholic–Orthodox split within Christianity. Although the schism had begun in the eleventh century over such issues as papal primacy, the addition of filioque to the Nicene Creed, and the use of leavening in eucharistic bread, bitter hostility between ordinary Catholics and Orthodox