The crucial step in Christianity's secularization of politics was the move from the Old Testament to the New Testament. The Mosaic political regime in the Old Testament became a theocracy that enforced its moral and religious law through persecution. By contrast, the Christian churches in the New Testament were voluntary groups that enforced moral and religious conformity among their members without legal coercion.
After the conversion of the Roman Emperor Constantine in 311, Christianity eventually became the exclusive religion of the empire, and this allowed the Christian Church to use legal coercion against pagans and heretics, which included the execution of heretics. The Catholic Church developed a theory of persecution that prevailed in the Middle Ages.
As a consequence of the Protestant Reformation, Protestants argued against the Catholic persecution of Protestants as heretics. But once the Protestants gained political power, they persecuted Catholics, and the different Protestant churches persecuted one another. This conflict provoked a debate over the possibility of a legal toleration that would allow for the peaceful coexistence of the differing religious traditions. Eventually, this led to the development of the modern liberal doctrine of religious liberty.
More clearly than any other Christian author in the Reformation, Roger Williams saw that legal toleration to protect the liberty of conscience was a return to the original position of New Testament Christianity as opposed to the Mosaic regime of persecution in the Old Testament. For, as he declared in The Bloody Tenant of Persecution in 1644, "Persecutors seldom plead Christ but Moses for their author" (BT, 58).
Williams was one of those very few people in the Reformation who argued against persecution not only when he was its victim, but also when he had the power to become a persecutor. He was expelled from the Massachusetts Bay Colony for condemning the Puritan rule there as a Mosaic theocracy that was contrary to the New Testament, and for arguing that the American Puritan settlers should pay for the land that they had stolen from the American Indians. He then settled in what would become Rhode Island, established amicable relations with the Indians there, and founded a political community that extended legal toleration to all religions, although Williams was vigorous in trying to persuade those he regarded as pagans, blasphemers, and heretics to correct their moral and theological errors. The radical character of Williams's argument was widely recognized: shortly after its publication, The Bloody Tenant was burned by order of the British House of Commons.
Locke's Letter Concerning Toleration was published forty-five years after Williams's Bloody Tenent, and the range of Locke's toleration fell short of Williams's. Williams argued for tolerating all pagans, Jews, Muslims, Protestants, and Catholics. But Locke refused to extend toleration to Catholics and atheists. Williams never says specifically that atheists are to be tolerated. Some scholars assume that when Williams speaks of tolerating "Antichristians," this must mean atheists. But clearly for Williams, "Antichristians" refers to Catholics or "papists"--those who are "false Christians" submitting to the Pope as the Antichrist (BT, 134, 179). But it's significant that Williams never specifically states that atheists subvert social order, as Locke does.
Moreover, that Williams's legal toleration would protect atheists as well as believers is suggested by his radical separation--or what he called "wall of separation"--between church and state. He interprets Romans 13 as teaching that the civil magistrates have authority only of a "civil nature" for "the good and peace of their civil state," while the Kingdom of Christ has authority of a "spiritual and of a Soul-nature" (BT, 108-109). Civil magistrates have charge of "the bodies and goods of the subject," while the spiritual officers of Christ's church have charge of "their souls and soul safety" (BT, 127). The "civil sword" for "defense of persons, estates, families, liberties of a city" does not extend to "spiritual and soul-causes" (BT, 160). There are "diverse sorts of goodness," and "civil or moral goodness" is distinguished from "spiritual goodness" (BT, 245-46, 331-34).
If government is restricted to securing "civil peace" or "a civil way of union," then every church can exist like any voluntary group that has no authority to use legal coercion (BT, 72-73). Like any voluntary group, a church can follow the pattern of the churches in the New Testament that used excommunication as the ultimate punishment for those who departed from the orthodox beliefs and conduct of the church (see, for example, I Corinthians 5:13). But "excommunication is not persecution" (BT, 91, 116, 192).
Williams argued that Constantine and the good Roman emperors did more harm to Christianity through their persecution of heretics and pagans than did Nero in his persecutions of the Christians (BT, 184). In adopting legal toleration, Christians can return to the true teachings of Christ and the early Christians, who refused to imitate Moses in setting up a national church.
Although Locke's toleration is not a radical as Williams's, Locke does see as well as Williams the contrast between the Old Testament and the New Testament. Like Williams, Locke relies on the New Testament to support his argument for toleration. In his Letter Concerning Toleration, Locke cites the Bible at least 18 times, and only 5 of these are references to the Old Testament. He observes that while the Jewish commonwealth in the Old Testament was an "absolute theocracy," "there is no Christian commonwealth" in the New Testament (42, 189).
Williams and Locke were able to support their argument for toleration with a plausible reading of the New Testament. By contrast, it's hard to support any argument for persecution as compatible with the New Testament.
One example of this is the parable of the tares and the wheat (Matt. 13:24-30). Jesus compares the kingdom of Heaven to a man who sows good seed in his field, but then his enemy sows tares (weeds) among the wheat. When they sprout, the wheat and the weeds are mixed together, and the man's servants offer to pull up the weeds. But the man says that this should not be done, because any rooting up of the weeds will likely root up some wheat as well. So he allows the plants to grow together until the harvest, when the reapers will gather together the weeds to be burned, and gather the wheat into the barn.
While the interpretation of parables is often difficult, the meaning here seems reasonably clear: in this life, it is hard to separate true Christians from those who are not, but at the day of judgment in the afterlife, the true Christians will be rewarded with eternal life, and the unsaved will be eternally punished in Hell. This was the interpretation Williams used to support legal toleration: the unbelievers and the false Christians must be left alone and not persecuted, because at the time of harvest at the Last Judgment, they will be recognized by God and condemned to eternal punishment (BT, 112-13).
Augustine, however, developed a twisted interpretation of this parable to support persecution. When the weeds are clearly identifiable as different from the wheat, persecutors have a Christian duty to uproot the weeds without disturbing the wheat. This perverse reading of the parable of the tares was adopted by the medieval Catholic Church to support its theory of persecution.
Notice that Williams's reading of the New Testament allows him to combine legal toleration and moral and theological absolutism. Often the critics of toleration complain that it rests upon moral and theological relativism--that toleration assumes that there are no absolute standards of right and wrong. But with Williams, this is not true. He was morally and theologically intolerant, even as he argued for legal tolerance. He was sure that the New Testament provided absolute standards of right and wrong rooted in divine truth, and he was sure that the errors of his opponents would be punished by God in the afterlife. But while in this life, he would try to expose these errors through persuasion, he had no moral or religious right to use coercion to suppress the liberty of conscience of those who disagreed with him. This must be so, because freedom of thought is the precondition for Christian virtue. There is no moral or theological virtue in being coerced into a hypocritical profession of belief.
This indicates the classical liberal or libertarian character of New Testament Christianity as manifested in Williams's writings. This line of reasoning is elaborated in a remarkable book by Andy Olree, The Choice Principle: The Biblical Case for Legal Toleration. Olree writes primarily for evangelical Christians, trying to persuade them that Williams was right about the New Testament teaching toleration, and that such toleration really is compatible with a Christian belief in the absolute moral and theological truth of the New Testament, as long as one understands that the New Testament teaching about freedom of choice supplants the Old Testament teaching about theocracy and persecution.
In defending "legal toleration," Olree expands the argument for religious toleration into a general argument for the legal toleration of both religious and moral pluralism. Thus, Olree argues against the "legal moralism" of many evangelicals and of Catholics like Robert George who assume that any good regime must legally coerce people into virtue, by outlawing immoral behavior, which Olree rejects because it cannot work, because it promotes a denial of human liberty, and because it contradicts the teaching of the New Testament.
In arguing for a combination of liberty and virtue--liberty as secured by government and virtue as cultivated in the natural and voluntary associations of civil society--Olree takes a position that is similar to the Christian libertarianism of Frank Meyer and the Aristotelian liberalism of Douglas Rasmussen and Douglas Den Uyl. They all argue that, far from being contradictory, political liberty protects the freedom of choice that is the precondition for moral virtue.
A commonly cited New Testament passage to support persecution and legal moralism is the teaching of Romans 13 that rulers are God's servants "to execute wrath on the wrongdoer." One of the best parts of Olree's book is his interpretation of this teaching (84-88, 106-10, 113-15, 120-24, 146-47). The primary question here is the meaning of "wrongdoing." Olree argues that both the historical context and the textual context suggest that the "wrongdoing" that is rightly punished by government refers only to actions of people that directly harm or victimize others.
First, the historical context for this scriptural passage is that Nero is the Roman Emperor. During Nero's time, Roman law was used to support pagan worship, which was sinful to the Christians, and it allowed for sinful activities such as prostitution, homosexuality, and abortion. So, clearly Paul was not interpreting "wrongdoing" as all conduct that would be sinful according to the Bible.
Second, the textual context is that immediately prior to Romans 13--at the end of Romans 12--Paul condemns vigilante vengeance ("Do not repay evil for evil," because vengeance belongs to God). Thus, by implication, Olree concludes, the rulers seen as God's servants in punishing wrongdoers in Romans 13 are exercising collective vengeance as a legal substitute for individual vengeance, so that the "wrongdoing" being punished by government is any wrong that would so harm or victimize people that they would naturally want to take vengeance. Such "wrongdoing" would be acts of force or fraud that victimize others rather than personal sins.
Olree applies this libertarian reading of the New Testament to the legal and moral debates over suicide, homosexuality, drug addiction, redistributive taxation, prostitution, and abortion. In each case, he argues for the "choice principle"--that law rightly secures individual choice or autonomy except in those cases where individuals have imposed some direct harm--by force or fraud--on others. In the case of abortion, he takes no clear position, except to argue that whether we should legally prohibit abortion as murder turns on the question of whether human life begins before birth, which he takes to be a question that the Bible does not answer.
The plausibility of this libertarian reading of the New Testament as supporting legal toleration and religious liberty was dramatically manifested in the Second Vatican Council of the Catholic Church, particularly in the Declaration of Religious Freedom approved in 1965. Under the influence of liberal Catholics such as John Courtney Murray, the Vatican Council declared that "the human person has a right to religious freedom." In section 12, the Council stated:
"In faithfulness therefore to the truth of the Gospel, the Church is following the way of Christ and the apostles when she recognizes and gives support to the principle of religious freedom as befitting the dignity of man and as being in accord with divine revelation. Throughout the ages the Church has kept safe and handed on the doctrine received from the Master and from the apostles. In the life of the People of God, as it has made its pilgrim way through the vicissitudes of human history, there has at times appeared a way of acting that was hardly in accord with the spirit of the Gospel or even opposed to it. Nevertheless, the doctrine of the Church that no one is to be coerced into faith has always stood firm."Is the Catholic Church confessing here that its earlier doctrine of persecution was contrary to the New Testament--"a way of acting that was hardly in accord with the spirit of the Gospel or even opposed to it"? Does this concede that Roger Williams was right about the New Testament supporting toleration and liberty, while the medieval Church and the Protestants who supported persecution were wrong?
Do we see a continuation in this movement of the Catholic Church towards Christian libertarianism in that Popes John Paul II and Benedict XVI have asked forgiveness for the Church's history of supporting the violence of persecution?
Some of these points are elaborated in other posts here, here, here, here, and here.
John Locke, A Letter Concerning Toleration and Other Writings, ed. Mark Goldie (Indianapolis: Liberty Fund, 2010)
Andy G. Olree, The Choice Principle: The Biblical Case for Legal Toleration (Lanham, MD: University Press of America, 2006)
Roger Williams, The Bloudy Tenent of Persecution, in The Complete Writings of Roger Williams, ed. Samuel L. Caldwell (New York: Russell & Russell, 1963), vol. 3.