Most elites in the West believe that undomesticated Christianity is hostile to human freedom. A persecutory relic of the past, it must be chastened before it can participate in liberal society. In one of the final books before his death, for example, John Rawls takes Christianity’s political illiberalism as a fact of “historical experience”—not a failure of Christianity to live up to its ideals, but part of its very essence. He further writes that the “content and tone” of his theory of justice was influenced by pondering  the “endless oppressions and cruelties of state power and inquisition used to sustain Christian unity beginning as early as St. Augustine and extending into the eighteenth century.”

Many scholars agree. They argue that Christian advocates of political liberalism and religious liberty were not really Christian (John Locke) or motivated by Christian convictions (Roger Williams); that the most zealous Christian advocates of liberty (the Radical Reformation) were marginal to the mainstream Christian tradition; and that the apparently liberal politics of genuine Christian leaders (Pope Pius XII) turned out to be illiberal and restrictive after all. “In this narrative,” Timothy Samuel Shah writes, “Christianity was the great moral and political problem to which Enlightenment liberalism was the necessary solution.”

Shah and his colleagues at Georgetown’s Religious Freedom Research Project argue otherwise. Christianity and Freedom came out of a two-year research initiative examining the historical development of Christian thought on religious freedom and the freedom of contemporary Christians around the world. The results show how Christians have helped develop key concepts of liberty, usually in response to persecution. Religious liberty, freedom of conscience, notions of human rights and human dignity, limited government, and the differentiation of religious and political authority—all have religious roots.

As Shah and Robert Louis Wilken demonstrate, reflection on religious freedom began in the earliest days of the Church. The authors of the New Testament saw persecution as a consequence of Christian life, an expected aspect of participating in Christ’s work, death, and resurrection. Christians in the following generations sought to argue against Roman persecution, but the pagan philosophical tradition offered no conceptual help. The first substantive argument against persecution comes from Athenagoras’ “Plea for Christians,” written to the emperor Marcus Aurelius and his son Commodus (ca. 175 AD). In the Plea, Athenagoras argues that a Roman magistrate should seek to promote an upright citizenry that refrains from evil, and that civic virtue requires a genuine “fear of the divine.”  In order to have a genuine fear of the deity, Athenagoras writes, “It is necessary for all men to venerate as gods those whom they wish.” In other words, civic virtue requires religious toleration—for all people, not just Christians.

Tertullian echoed Athenagoras’ argument in his Apology (ca. 197–198 AD), where he writes that without free choice of worship, religious practice becomes “impious” and incapable of fostering civic virtue and imperial pride. But in a letter to a proconsul of Carthage in 212 AD (Ad Scapulam), he makes the first argument in Western history for the universal human right of religious liberty: “It is a human right (humani iuris) and a natural power or natural privilege (naturalis potestatis) that one should worship whatever he intends (quod putaverit colere); the religious practice of one person neither harms nor helps another.” In short, Tertullian argues that religious belief and practice should not be coerced and that the right of their free exercise is natural, preceding the state and not determined by it.

Next came Lactantius, tutor to the son of Constantine and author of the Divine Institutes, which were read aloud in Constantine’s presence. Against Roman persecutors, he argued that religion was not simply a matter of ritual and ceremony, but of interior disposition. Religion must be dealt with by words and not by violence, he wrote, since it pertains to the will: “The worship of God . . . requires full commitment and faith. For how will God love the worshipper if he himself is not loved by him, or grant to the petitioner whatever he asks when he draws near and offers his prayer without sincerity or reverence. But they [the Romans], when they come to offer sacrifice, offer to their gods nothing from within, nothing of themselves, no innocence of mind, no reverence, no awe.”

Wilken points to one clear source of this understanding of religious liberty: the Bible. Tertullian quotes Genesis 1:26–27, which speaks of human beings as free and made in the image and likeness of God, several times in his writings and understands free will to be the clearest sign of that resemblance. Kyle Harper of the University of Oklahoma argues that such passages of scripture gave Christians a new understanding of human dignity as well. He notes that “none of the classical political regimes, nor any of the classical philosophical schools, regarded human beings as universally free and incomparably worthy creatures. Classical civilization, in short, lacked the concept of human dignity.”

Instead, it arose out of Christianity’s encounter with three institutions in Roman society. The world’s first record of opposition to slavery as an institution comes from a homily on Ecclesiastes by Gregory of Nyssa, who condemns slave ownership because it violates the free nature of human beings. While Gregory did not launch a movement, he shows the new understanding of human dignity that Christianity had injected into the pagan world. Efforts for relief of the poor were more effective. Indeed, Christianity created the social category of “the poor” for persons whose poverty was an affront to their dignity. And Christian solicitude for prostitutes and other victims of sexual coercion resulted in a fifth-century Byzantine decree against pimps. “For the first time,” Harper writes, “the bodies of those without any familial or civic claim to sexual honor received the protection of the state, simply by virtue of their human dignity.”

In short, Christianity was not a threat to the dignity of vulnerable women and the poor. Rather, it gave them a sense of worth they had not known. Rebecca S. Shah’s study of Dalit (untouchable) converts to Christianity shows that this is still true. Her research echoes the words of a Dalit convert in a survey in 1931: “I wanted to become a Christian so I could be a man. None of us was a man. We were dogs. Only Jesus could make men out of us.”

Christianity gives Dalits in Indian slums hope, the belief that a transcendent power can influence their lives. Hope, in turn, “gives the poor a sense of security in a caring and responsive providence to enable them to take risks and make choices that could lift them and their families out of poverty.” Tithing and fasting foster a culture of self-restraint, which shields the poor from “myopic overconsumption” and helps them use their money wisely. Human dignity raises their horizons, Shah argues, especially those of women, empowering them economically and domestically. And female converts to Pentecostal Christianity are more likely to take action in face of domestic abuse by telling their pastor, who can mediate on their behalf.

To tell this side of the story is not to efface the ways in which Christians betrayed the principles of their faith and fought against freedom of religion, freedom of conscience, and human dignity. Lactantius laid the groundwork for the Edict of Milan in 313, which gave “to the Christians and to all men freedom to follow whatever religion each one wished.” As Christianity gained cultural power, its intellectual leaders began to write against the religious coercion that arose. Gregory the Great and Cassiodorus wrote against the forced baptism of Jews and urged that they be allowed to worship as they pleased in synagogues. But by the High Middle Ages, Ian Levy records, many thinkers permitted coerced conversion as long as it did not entail “being physically seized upon and violently dragged to the baptismal font.”

The Wars of Religion and the colonization of the New World were dark periods for Christian liberty. Nonetheless, as David M. Lantigua recounts, Bartolomé de las Casas made a strong, unswerving case for the human dignity and religious liberty of South American native peoples. Moreover, as John Witte, Jr., David Little, and Matthew J. Franck show, Calvin and his followers provided an important foundation for American democratic thought.

Daniel Philpott further argues that Christian thinkers made important contributions to the development of liberal democratic institutions between 1800 and 2000. These included Felicté de Lammenais, Henri-Dominique Lacordaire, Abraham Kuyper, Hermanus J. A. M. Schaepman, Lord Acton, Jacques Maritain, and John Courtney Murray, S.J. They advocated an expansion of liberty on distinctively Christian grounds, frequently in an atmosphere in which their own religious liberty was under attack. These thinkers were Christian liberals, Philpott writes, not liberal Christians: “They did not simply come around to accepting theories of liberal democracy that others had developed without reference to God.” Rather, their political theology called for religious liberty and impelled them to help develop and defend liberal democratic institutions.

What about Christians in our own time? Here Christianity and Freedom turns its gaze toward the global persecution of Christians and their response. The scholars define persecution according to the U.S. International Religious Freedom Act of 1998, which includes prohibitions on religious assemblies, conversion, free speech, and possession of religious literature. According to Todd M. Johnson, an eminent scholar of religious demography at Gordon-Conwell Seminary, 500 million Christians (22% of the global total in 2010) live in states subject to persecution. As Alan D. Hertzke of the University of Oklahoma notes, during a six-year study by the Pew Research Center, “Christians suffered harassment at some point in a total of 151 countries, more than that of any other religious group,” and “in more diverse settings and across a wider geographic span.” Evangelicals, charismatics, and Eastern Orthodox experience more persecution, in part because the largest Catholic-majority countries have little to none.

According to Johnson, persecutory states fall into five categories: communist states, national security states (such as Burma, Uzbekistan, and Belarus), South-Asian religious nationalist states, and Muslim-majority states. A further 208 million Christians live in Western secularist states, where they might face lesser discrimination, which Pope Francis calls “polite persecution.” Paul Marshall of Baylor University points to the case of a British hospital which asked a nurse not to wear her cross on her necklace, though she had done so for thirty years. In 2013, the European Court of Human Rights ruled that she had not suffered religious discrimination. During the review of the case, the lawyer representing the British government said that the hospital’s act did not prevent her practicing her religion in private—a conception of religious liberty that contradicts article 18 of the Universal Declaration of Human Rights.

In examining the reasons that these different regimes persecute, Marshall writes that there are many factors and nothing amounting to a “unitary war on Christians.” However, he continues, the Christian distinction between the roles of church and state “manifests itself practically in a denial that the state is an all-encompassing or the ultimate arbiter of human life. Hence this belief is a foundation for social and political pluralism. Accordingly, Christians are often subject to persecution by those who have a monistic conception of the social order and the state—that there is one order of authority in society, whose reach applies to every person and institution and to which all must submit.”

These scholars also provide concrete markers of the astonishing growth of Christianity during the past century. In 1900 Africa had 10 million Christians; in 2000, it had 360 million. The countries with the highest percentage of Christians in 1910 were in Western Europe and the Caribbean; in 2010, they were in Eastern Europe or Latin America. Marshall records that some three quarters of the world’s 2.2 billion nominal Christians live outside the developed West, as do perhaps four fifths of the world’s active Christians. The average Christian is therefore less likely to be the descendent of crusaders and colonists than “a Brazilian or Nigerian woman or a Chinese youth.”

Christianity and Freedom shows that elite and scholarly assumptions about Christianity are incomplete. Christians have been in the vanguard of the historical expansion of liberty. They developed unprecedented concepts of liberty that we now take for granted. Shah notes that while the European Enlightenment built on earlier Christian thought, the “Patristic Enlightenment” formed its understanding of religious freedom with little historical precedent. Given that lack of historical precedent, it is only because of prior Christian thought about liberty and human dignity that the Enlightenment could build at all. As Kyle Harper puts it, we would not have had Kant without Constantine.

Some Christians have perpetrated acts of violence and oppression, but they have been a disappointment to their faith, not its natural working-out. The fathers of liberal democracy could critique Christianity’s failures because of the core principles it had failed. Moreover, an increasing percentage of the world’s Christians are likely to suffer for their faith, in the vast majority of cases without reprisal. As it did in Late Antiquity, Christianity gives them a wider horizon of freedom and dignity than they saw before. It offers deeper roots for liberty and dignity than Rawls’ justice-as-fairness, and without imposing a quasi-religious secularism at the expense of full-blooded faiths. Hence, Allen Hertzke concludes, “the advance and maintenance of freedom around the globe are tied to the fate of Christianity.”