The part of the Bill of Rights that is most important to the separation debate is the First Amendment, in particular, the two religion clauses of the first Amendment. These clauses deal precisely with the issue of what government can and cannot do with respect to religion. Below, we lay out the wording of these clauses, and what is at issue in their interpretation.
The establishment clause makes up the first ten words of the First Amendment. It reads as follows:
Congress shall make no law respecting an establishment of religion...
The free exercise clause makes up the next six words of the Amendment. It reads as follows:
or prohibiting the free exercise thereof;
Together, these clauses comprise the most specific statement in the Constitution about the powers of the federal government over religion. It is interesting, for example, to note that both clauses are phrased in the negative, that is, they describe what the federal government cannot do with respect to religion. Hence, if the framers gave some power to the federal government over religion, they must have specified it elsewhere in the Constitution.
While both clauses are important to religious liberty, it is the establishment clause that has become of the focus of the current debate over separation. In particular, the clause is generally interpreted in one of two mutually exclusive ways. The narrow interpretation (favored by accomodationists), holds that the clause bans only the establishment of a state church or religion. A classic statement of this position is found, for example, in J. M. O'Neill's Religion and Education Under the Constitution, p. 56, where he holds that the First Amendment proscribes only "a formal, legal union of a single church or religion with government, giving the one church or religion an exclusive position of power and favor over all other churches or denominations." On this line Congress might do any of a number of things that aid religion so long as it doesn't directly establish a state church.
In contrast, separationists favor what is known as the broad reading of the First Amendment. This reading holds that the First Amendment bans not only the establishment of a state church, but the establishment of any religious belief or practice by law. Hence, separationists would hold that, eg., when government requires prayer in the public schools, it establishes a religious practice and is, hence, illegal. The classic statement of this position is Justice Black's majority opinion in Everson v. Board of Education. These issues are discussed throughout our section of the web page devoted to the case for separation.
Some other controversies concern the interpretation of the word "establishment" in the First Amendment, what the framers meant by "respecting" establishment, and why the framers modified the word establishment with the word "an." We take on all these issues in our section on the grammar of the establishment clause.