" Some religions, such as Catholicism, fully endorsed slavery, as Pope Nicholas V made clear when, in 1452, he issued the radically proslavery document Dum Diversas. This was a papal bull granting Catholic countries such as Spain and Portugal “full and free permission to invade, search out, capture, and subjugate the Saracens and pagans and any other unbelievers and enemies of Christ wherever they may be, as well as their kingdoms, duchies, counties, principalities, and other property … and to reduce their persons into perpetual slavery.”10 These last few words—to reduce their persons into perpetual slavery—sound not just sinister to us, but also psychotic. They make perfect sense, however, in a Christian context, given that the Bible is itself a heedlessly proslavery tome. "

― Michael Shermer , The Moral Arc: How Science and Reason Lead Humanity toward Truth, Justice, and Freedom