That's actually not entirely true. St. Thomas Aquinas taught that slavery was a sin in the 13th century. Several Medieval and Renaissance popes condemned slavery, as well. On the Eastern side of Christianity, slavery was mostly phased out by the 11th century in the Byzantine Empire.

So in short, the institutional powers of the Roman Catholic Church and the Eastern Orthodox Church were greatly responsible for the end of slavery in Europe. (Serfdom wasn't much better, but it was progress.) I suspect that anti-Christian bias is a big reason why pre-Enlightment abolitionism is swept under the rug.

That's actually not entirely true. St. Thomas Acquinas taught that slavery was a sin in the 13th century. Several Medieval and Renaissance popes condemned slavery, as well. On the Eastern side of Christianity, slavery was mostly phased out by the 11th century in the Byzantine Empire.

So in short, the institutional powers of the Roman Catholic Church and the Eastern Orthodox Church were greatly responsible for the end of slavery in Europe. (Serfdom wasn't much better, but it was progress.) I suspect that anti-Christian bias is a big reason why pre-Enlightment abolitionism is swept under the rug.