"Neither a state nor the Federal Government can, openly or secretly, participate in the affairs of any religious organizations or groups and vice versa. In the words of Jefferson, the clause against establishment of religion by law was intended to erect 'a wall of separation between church and state.'" [Hugo L. Black, U.S. Supreme Court Justice, majority opinion in Everson v. Board of Education, 330 U.S. 1 (1947)]