It is human nature for individuals to reach different conclusions about what is true, and to be convinced that one’s beliefs, being true, deserve to prevail over false beliefs. The diversity of our opinions and our zeal in advancing them, wrote James Madison, has “divided mankind into parties, inflamed them with mutual animosity, and rendered them much more disposed to vex and oppress each other than to cooperate for their common good.” This dilemma is thus “sown in the nature of man,” and the resolution to it of late-18th century Americans was the disestablishment of religion: first, through the No Religious Test Clause of Article VI of the Constitution, and later, the Establishment Clause of the First Amendment.

Today it is commonly thought that disestablishment was a deist or Enlightenment project aimed at achieving national cohesion by suppressing religion. That view is ahistorical, however. As Eric Voegelin observed, although the debate of the American Revolution “was already strongly affected by the psychology of Enlightenment,” it “also had the good fortune of coming to its close within the institutional and Christian climate of the ancien régime.” Disestablishment did not reflect a war on religion but was rather a political settlement reached by antagonistic religious factions. Madison, the author of the First Amendment, described this arrangement as “an entire abstinence of the government from interference [with religion] in any way whatever, beyond the necessity of preserving public order, and protecting each sect against trespasses on its legal rights by others.” This settlement reflected the practical conditions of the time: none of the factions was powerful enough to establish itself over the others, and none was willing to risk a constitutional arrangement that permitted established religion out of fear that another sect might dominate them in the future. Arguing in the North Carolina Convention for ratification of the Constitution, future Supreme Court justice James Iredell explained that Article VI was “calculated to secure universal religious liberty, by putting all sects on a level–the only way to prevent persecution”…