First Amendment: Free Exercise Clause (1791)
This clause protects an absolute freedom of belief. The Founders saw religious liberty as a natural right, and so the First Amendment ensures that all people have an equality of rights to practice their faith. While originally written to apply to actions of the federal government, it was incorporated into state governments through the Fourteenth Amendment by the Supreme Court in the case Cantwell v. Connecticut (1940).
Precursors to the Free Exercise clause include the English Bill of Rights, the Virginia Declaration of Rights, and the Virginia Statute for Religious Freedom. The English Bill of Rights expanded religious freedom for Protestants who did not attend the Church of England, but not for Catholics or non-Christians. The Virginia Declaration of Rights held that “all men are equally entitled to the free exercise of religion.” The Virginia Statute for Religious Freedom asserts that “all men shall be free to profess, and by argument to maintain, their opinion in matters of religion.”