Slavery originated during the age of savagery and continued into ancient civilizations. Slavery was there in Babylon and elsewhere in Mesopotamia; it was widely prevalent in ancient Egypt, Greece and Rome, centuries before the coming of Christ. Ancient India also had slaves but they were so mildly treated that foreign visitors like Megasthenes, who were acquainted with their fate in other countries, failed to notice the existence of slavery in this country.
An altogether new dimension—religious sanction—was added to the institution of slavery with the rise of Christianity to power in the Roman Empire. Hitherto, slavery had been a creation of the crude in human nature—the urge to dominate over others, to make use of others for private comfort and profit.
Now it was ordained that the God of the Christians had bestowed the whole earth and all its wealth on the believers, that the infidels had no natural or human rights, and that the believers, that the infidels had no natural or human rights, and that the believers could do to the infidels whatever they chose—kill them, plunder them, reduce them to the status of slaves or non-citizens. In short, slavery became a divinely ordained institution.