Since there is disagreement, it might be interesting to know how those who were most directly responsible for this law viewed it. The two people whose opinions are the most significant on this question are James Madison and Thomas Jefferson. Madison, the “father of the Constitution,” actually drafted the religion clauses. Jefferson, his mentor, was the author of the Virginia Statute for Religious Freedom, which strongly influenced Madison, and the person who convinced Madison of a need for a Bill of Rights – one “providing clearly for freedom of religion.” And how did they view the matter? As it turns out, both of them interpreted the religion clauses broadly.
That this is the case can be seen from a variety of examples. For instance, when he was president, Madison vetoed a bill that would have given federal land to a church because it would have set “a precedent for the appropriation of funds of the United States for the use and support of religious societies.” He was against the appointment of chaplains to Congress for similar reasons, and there were several other instances during his presidency that clearly show he read the First Amendment clauses rather broadly. And Jefferson had if anything even stronger opinions on this. His position is very clear: in a well-known letter to a group of Baptists, he wrote about his reverence for “that act of the whole American people which declared that their legislature should 'make no law respecting an establishment of religion, or prohibiting the free exercise thereof', thus building a wall of separation between church and state” [emphasis added].
Members of the religious right are quick to point out that the phrase “a wall of separation between church and state” is nowhere to be found in the Constitution. While that is true, it is clear that both Jefferson and Madison believed that the idea it expresses is implied by the First Amendment.
As with Part 1, the main source for the above information was The Godless Constitution, by Isaac Kramnick and R. Laurence Moore.