The original thirteen states that formed the United States included individuals from a variety of religious traditions. To ensure that the national government respected freedom of belief, freedom of conscience, and freedom of religious practice, the First Amendment prohibited the federal government from either establishing a national church or interfering with existing state religions. Since then the Supreme Court has created various "tests" to determine if government practices violate the Establishment Clause of the First Amendment. This lesson explores the history and principles behind this clause.