"But fighting slavery is nothing new for Christians. After all, Christianity was born into a world where chattel slavery, one person owning another, was the cornerstone of the economy.
Ironically, many famous historians, including those most critical of Christianity, were indifferent about the role that slavery played in antiquity. Edward Gibbon called the "cruel treatment" of slaves "almost justified by the great law of self-preservation."
Western Christianity saw matters differently. Its spread through western Europe was accompanied by calls for an end to chattel slavery. Saint Bathilde, the wife of the seventh-century Frankish king Clovis, was canonized, in part, for her efforts to free slaves and end the slave trade.
The result of hers and similar efforts was that, by the eleventh century, slavery had been effectively abolished in western Europe.
The lone exceptions were areas under pagan or Muslim control. By the time Thomas Aquinas wrote the Summa Theologica in the thirteenth century, slavery was a thing of the distant past. That's why Aquinas paid little attention to the subject, devoting himself instead to the issue of serfdom, which he considered "repugnant.""
Christianity and Slavery