4 From the first sin came all evils, and specially this perversity that there were men who, forgetful of the original brotherhood of the race, instead of seeking, as they should naturally have done, to promote mutual kindness and mutual respect, following their evil desires began to think of other men as their inferiors, and to hold them as cattle born for the yoke. In this way, through an absolute forgetfulness of our common nature, and of human dignity, and the likeness of God stamped upon us all, it came to pass that in the contentions and wars which then broke out, those who were the stronger reduced the conquered into slavery; so that mankind, though of the same race, became divided into two sections, the conquered slaves and their victorious masters. The history of the ancient world presents us with this miserable spectacle down to the time of the coming of our Lord, when the calamity of slavery had fallen heavily upon all the peoples, and the number of freemen had become so reduced that the poet was able to put this atrocious phrase into the mouth of Caesar: "The human race exists for the sake of a few."(5)
Source: In Plurimis (Vatican.va)