IN 1802, in a letter to the Danbury Baptist Association, Thomas Jefferson wrote that the First Amendment had the effect of “building a wall of separation between Church & State.” As it happens, when Congress drafted the First Amendment in 1789, Jefferson was enjoying Paris. Nonetheless, his words about separation are often taken as an authoritative interpretation of the First Amendment’s establishment clause. Indeed, in the 1947 Everson v. Board of Education decision, the Supreme Court quoted Jefferson’s pronouncement to justify its conclusion that the First Amendment guarantees a separation of church and state. Not only the justices but also vast numbers of other Americans have come to understand their religious freedom in terms of Jefferson’s phrase. As a result, Jefferson’s words often seem more familiar than the words of the First Amendment itself.