Separation of church and state refers to the First Amendment''s Establishment Clause, which states "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof." Though the phrase "separation of church and state" doesn''t appear in the Constitution, Thomas Jefferson coined the metaphor in his 1802 letter to the Danbury Baptist Association, describing "a wall of separation between the church and state." Roger Williams, Rhode Island''s founder, first used similar language advocating for "a wall or hedge of separation" between government and religion. In Everson v. Board of Education (1947), the Supreme Court applied this principle to states, with Justice Hugo Black declaring "the First Amendment has erected a wall between church and state. That wall must be kept high and impregnable." Jefferson and James Madison argued that forcing citizens to financially support religions they didn''t follow through taxation violated natural rights to religious liberty, establishing the principle that government cannot favor particular faiths or religion generally.