The phrase “separation of church and state” does not appear in the Constitution. What does appear is the opening of the First Amendment: “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof.” Those two clauses, the Establishment Clause and the Free Exercise Clause, are where every modern dispute starts.
Where the phrase comes from
In an 1802 letter to the Danbury Baptist Association, President Thomas Jefferson described the First Amendment as “building a wall of separation between Church & State.” The Supreme Court quoted the letter in Reynolds v. United States (1879) and again in Everson v. Board of Education (1947), the case that applied the Establishment Clause to state governments.
The Establishment Clause: government can’t sponsor religion
Key cases include Engel v. Vitale (1962), which barred official prayer in public schools, and Lemon v. Kurtzman (1971), which created a three-part test asking whether a law had a secular purpose, primarily advanced or inhibited religion, or excessively entangled government with religion. In Kennedy v. Bremerton School District (2022), the Court said it had abandoned the Lemon test and that the clause should be read by reference to “historical practices and understandings.” That shift matters: courts now ask whether a practice resembles what the founding generation accepted.
The Free Exercise Clause: government can’t suppress religion
In Employment Division v. Smith (1990), the Court held that neutral laws that apply to everyone generally do not violate free exercise, even if they burden a religious practice. Congress responded with the Religious Freedom Restoration Act of 1993, which requires the federal government to show a compelling interest before substantially burdening religion. RFRA was the basis for Burwell v. Hobby Lobby (2014). More recent cases, such as Carson v. Makin (2022), hold that when a state funds private schools, it cannot exclude religious ones.
Where the fights are now
- Religious exemptions from anti-discrimination rules. In Fulton v. City of Philadelphia (2021), the Court sided with a Catholic foster agency that would not certify same-sex couples. Several states, including Virginia in 2012, passed laws letting private adoption agencies decline placements on religious grounds.
- Religion in public schools. Laws requiring the Ten Commandments in classrooms and state-funded religious charter schools have reached the federal courts.
- Funding. Vouchers and education savings accounts raise the question of when public money may flow to religious institutions.
When a headline says a law “turns a state into a theocracy” or “bans religion,” read the bill. Most fights are about exemptions, funding and school settings, and the outcome usually turns on which of the two clauses a court thinks is at stake.