In the most famous passage of the Declaration of Independence, it is easy to see the connection between theism and human rights: “We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.” As I explained in God of Liberty: A Religious History of the American Revolution, Thomas Jefferson and the Continental Congress could have chosen more generic ways to explain the basis of equal rights (“all men are by nature equal”) but they decided to employ active, theistic language instead.

Because they operated in such a broadly Christian mental world, we can interpret the Declaration’s language as rooted in Christianity, not just general theism. But there’s evidence that the beginnings of “human rights” advocacy really did have specific, deep Christian roots.

I was fascinated to read Kyle Harper’s chapter “Christianity and the Roots of Human Dignity in Late Antiquity” in Timothy Shah and Allen Hertzke’s new volume, Christianity and Freedomfrom Cambridge University Press. (The price of the book will make it affordable only for large institutional libraries, but you can get it through Interlibrary Loan programs or wait for a paperback edition, which I am told is forthcoming.) Harper, an expert on Christianity in late antiquity, and the provost at the University of Oklahoma, notes that we commonly associate ideas of human rights with the “Enlightenment” of the eighteenth century, on which some of the Declaration draws.

But Harper posits that human rights advocacy—especially that all people have equal dignity—had key, if not unique roots in Christianity of the fourth through the sixth centuries. Why did these roots not appear earlier, we might ask? Harper answers that the difference from the early church is that Christians in the age of Constantine were moving into positions of power. They could hope to effect social change, in accord with Christian principles, for the first time.

The philosophers of Greek and Roman antiquity “lacked the concept of human dignity,” Harper explains. As Christianity became more widespread, leaders of the church developed more influence, and some rulers even became Christians. This “created the grounds for the development of human rights.”

I might have noted that you can find sources for universal human dignity in the Hebrew Bible as well. These advocates of late antiquity were drawing off of principles from both the Old and New Testaments. But starting in the AD 300s, “we find Christians, for the first time, in positions of sovereign control and social leadership, empowered rather than persecuted.”

What would they do with that power? We should not exaggerate the extent of their advocacy of human rights, but certain Christian writers did break away from longstanding social practices related to slavery, prostitution, and neglect of the poor. Based on Christian convictions, they sometimes made first-in-world-history arguments against these practices. They did not need to wait for Jefferson or Immanuel Kant to enlighten them.

Slavery is the most intriguing case. The institution, in which many people were treated (and mistreated) as commodities, was pervasive in the ancient world. Harper makes the uncomfortable but fair point that the Scripture itself did not contain immediately obvious passages which would absolutely prohibit owning slaves per se. We don’t have much evidence to suggest that the early church typically moved beyond the Pauline admonitions for slaves to obey masters, and for masters to treat slaves fairly.

This makes especially conspicuous a sermon of the fourth-century Church Father Gregory of Nyssa, in which he began to criticize slavery as an institution. As Harper notes, this is a breathtaking departure since we have no other such extant criticisms of slavery “from the entire ancient world.”

Although Gregory’s criticisms seem to have attracted little notice at the time, it was “no small distinction to be the earliest human to have left an argument for the basic injustice of slavery.” Quite a milestone!

Gregory’s sermon is on Ecclesiastes, and details the sins of those who have become prideful because of their wealth. In the ancient world, such pride was often manifested in the owning and maltreatment of slaves. Gregory does not just indict the masters for abusing slaves, however. He rages against the “sheer arrogance of slave ownership” itself. As made by God, humans were naturally free beings, and slavery made a mockery of their natural state.

Humans enjoyed mastery over the animal kingdom, but slave owners presumed to treat humans like a cow or horse. Not only did the slaves have to live at the command of another, but they could be bought and sold like any other market item. How could a rational being, created in God’s image, be given a man-made “price”? This cruelty was what nineteenth-century observers called the “chattel principle”—treating a God-made human like transferable property. It made slavery fundamentally sinful and arrogant.

Christian leaders made even more progress in their critique of prostitution, and the treatment of the poor. With regard to prostitution, Christian rulers helped to make many kinds of coerced sex illegal by the end of the fifth century, something that would have been unthinkable without Christian concepts of human dignity.

Elsewhere I have described “equality by creation” as the most powerful concept to emerge from the American Revolution. But really, it is a concept with deeper roots in the Judaeo-Christian tradition. Many Christians in antiquity, and for centuries afterward, continued to accept practices like chattel slavery. But the spread of Christianity opened unheard-of possibilities for reform, based on the notion that we all stand equal before our Creator.

— See also Kyle Harper’s book From Shame to Sin: The Christian Transformation of Sexual Morality in Late Antiquity (Harvard University Press).