In path-breaking works of constitutional history, Michael Kent Curtis has explored the ways that natural rights theory provided a foundation for the First Amendment freedoms of speech and press and the Fourteenth Amendment rights of American citizenship. In this Essay, I show that the Free Exercise Clause also was deeply influenced by natural rights theory, as well as by the closely related ideas of natural law and natural religion. Eighteenth-century Americans held that religion was rooted in reason. It followed that individuals had an inalienable right to use their own minds to form religious beliefs and to worship in accord with them. But the same natural law that protected religious liberty also enjoined individuals to respect the rights of others. After sketching this founding-era history, I discuss its implications for how we should approach the issue that arises in cases like Masterpiece Cakeshop, Ltd. v. Colorado Civil Rights Commission (2018). I argue that, as a general rule, the right to religious liberty should not be interpreted to mandate exemptions from general laws that are intended to protect the civil rights of other people, such as same-sex couples who seek goods and services in places of public accommodation.
