Early Christian Roots of Religious Freedom
The first person to claim freedom of religion as a right was Tertullian, a Christian teacher in Carthage, in a Latin treatise in defence of Christianity addressed to Scapula, the Roman proconsul, written ca. AD 211. Here’s the crucial opening statement:
“It is a human law [humani iuris] and a natural right [naturalis potestatis] that one should worship whatever he intends; the religious practice of one person neither harms nor helps another.”
In another treatise, Tertullian’s Apology, he uses for the first time in history the phrase “religious freedom.” Earlier, of course, Roman imperial authorities had granted toleration or privileges in matters of religion to certain groups, such as Jews. But granting a privilege is one thing, and claiming something as a natural right is quite another. It appears that the latter idea arose first among early Christian apologists.
Scholars have sometimes ascribed the notion of religious freedom to the so-called “Enlightenment,” often citing John Locke’s Letter on Toleration (1689) as the charter text and Locke as the initial champion of the idea. But in a small volume that arose from his 2014 Père Marquette Lecture, Robert Louis Wilken shows convincingly that “the roots of religious freedom in the west are to be found centuries earlier in the writings of Christian apologists who, in the face of persecution wrote to defend their right to practice the religion they wished without coercion”: The Christian Roots of Religious Freedom (Marquette University Press, 2014), 11-12.
Wilken tracks this emphasis forward from Tertullian through other early Christian figures, including Lactantius (a Christian apologist and contemporary of Constantine), who insisted that “Religion must spring from a free act” and cannot be coerced. Similarly, Alcuin, an advisor to Charlemagne, wrote forcefully to Charlemagne opposing his efforts to Christianize the Saxons by force.
Wilken then briefly explores likely biblical notions that influenced these writers, such as Paul’s statements about “conscience,” portrayed as an inner voice that urges action, even against the views of others (e.g., 1 Cor 10:23, 29).
Wilken takes us on a brief tour through key figures and developments of the middle ages, the Renaissance and Reformation, and the proliferation of varied religious groups and movements of the 16th and17th centuries. As he notes, the road wasn’t a straight one, and through this whole period, especially in various European nations, the notion persisted among many that political solidarity and loyalty required religious conformity, which was often coerced, recalcitrants often executed. But, amidst all this, the development and spread of ideas of religious freedom and liberty of conscience were fuelled in, and by, the emergence of dissenting religious groups, especially in the 16th century.
This involved also a separation between political loyalty and religion. Dissenters of that time insisted that they could be loyal to the ruler, even if they did not share his/her specific religion. Influential figures of those centuries included Roger Williams and William Penn. John Locke was a contemporary of Penn, and had met him in Holland. Locke’s Letter on Toleration appeared in Latin in 1689, some two decades after Penn’s Great Case for Liberty of Conscience (which was published in English). Moreover, Locke drew on the Bible in defending his views. Wilken concludes: “Though the idiom of Locke’s thought is different from that of Penn and Williams, his work is saturated with Christian assumptions drawn from the Scriptures and Christian tradition. His thinking cannot be understood without reference to Christianity” (38-39).
It will be particularly interesting to Americans, living now in a time of anxiety about religious differences that is being milked for cynical purposes at the highest political levels, to follow Wilken’s brief discussion of how early figures such as Madison and Jefferson as well show the influence of these ideas that emerged first in Christian writers of the early centuries.
But here’s Wilken’s final point made by others as well: Liberty of conscience was initially asserted and held dear in “an age of strong beliefs.” Religious freedom arose first among people who fervently believed that beliefs mattered greatly. “Liberty of conscience was born, not of indifference, not of scepticism, not of mere open-mindedness, but of faith” (46).
 Peter Garnsey, “Religious Toleration in Classical Antiquity,” in Persecution and Toleration: Papers Read At the Twenty-Second Summer Meeting and the Twenty-Third Winter Meeting of the Ecclesiastical History Society, edited by W. J. Shiels (Oxford: Basil Blackwell, 1984), 1-27.
My own most recent book: Destroyer of the gods: Early Christian Distinctiveness in the Roman World (Baylor University Press, 2016).