Tertullian, a North African Christian writer of the early third century, was the first to argue that because religious faith is an inward disposition of the mind and heart, it cannot be coerced by external forces. The Church Father writes:
It is only just and a privilege inherent in human nature that every person should be able to worship according to his own convictions; the religious practice of one person neither harms nor helps another. It is not part of religion to coerce religious practice, for it is by choice not coercion that we should be led to religion.
Tertullian is the first person in Western history to use the phrase “freedom of religion.” However, freedom of conscience has an even more ancient pedigree. The North African Tertullian draws upon various biblical evidence to support his argument, claiming that Jesus’s teaching that one should render unto Caesar what is Caesar’s and to God what is God’s communicates a separation of powers between the state and the church. The Apostle Paul, in turn, spoke of the Christian conscience as sometimes the judge of right action. In the Book of Daniel, the eponymous protagonist, as well as his friends Shadrach, Mescach, and Abednego, all reject Babylonian attempts to coerce them into pagan worship.
From Tertullian to the Reformation, there is a significant Christian tradition that affirms religious freedom....
...It is ultimately the Englishmen—Roger Williams, John Owen, William Penn, and John Locke—to whom America and the West are indebted for their conception of religious freedom. Williams argued that liberty of conscience applied to all men equally, including dissenting Christians, Jews, Muslims, and even the hated Catholics. He also “severed the link between the two tables of the law,” meaning that he rejected any role for the state in the affairs of the church and vice versa. Owen, in turn, interpreted Tertullian’s earlier cited argument to mean that “liberty of conscience is a natural right” rather than one created and protected by the state. Penn, meanwhile, argued that this liberty of conscience necessarily extended to public worship. Locke, finally, incorporated some of these elements, but went even further by arguing that religious communities are fundamentally voluntary societies composed of individuals possessing “free and spontaneous” rights.
...In truth, religion always extends beyond personal beliefs and corporate worship. It bleeds into the public square, informing the decisions of its citizens. Moreover, contra Locke, many religious communities do not view themselves as collections of autonomous individuals, but as corporate bodies that extend across society and across generations. There is an ancient, robust natural law tradition supporting this idea, one that looks to other societies, like the family and even the state, as examples of communities that also aren’t entirely voluntary. One does not choose his or her parents. Nor does one choose his or her nation. These things are givens. They may in time be rejected by individuals, though even then such bonds are impossible to fully shake off. Religion, like the family, remains a vinculum societatis, a unifying bond of society....