A friend of mine posted a bulletin concerning the Separation of Church and State, in which he lists quotes from the founding fathers about how important the Bible and Christianity is, and the obvious religious beliefs these people had. The obvious implication being how separate did the founding fathers really want religion from the state? Especially because "the separation of Church and State" doesn't appear in the Constitution of the United States.
What does appear in the Constitution is an Establishment Clause in the First Amendment, "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof..."
The framers of the Constitution did not want an established National Religion, nor did they want the government to be able to oppress a group because of their religious beliefs. This adheres pretty closely with John Locke's idea of social contract. This is the argument that government lacks authority over an individual's conscience, as it was something rational people could not give over to the government for it or others to control.
What resulted in America was a policy of religious tolerance, albeit a shaky one.
The actual phrase "separation of Church and State" doesn't show up in history until the beginning of the 19th Century, when Thomas Jefferson writes a letter to a small sect of Baptists, offering them reassurance that the government will leave them alone. He writes,
"Believing with you that religion is a matter which lies solely between Man and his God, that he owes account to none other for his faith or his worship, that the legitimate powers of government reach actions only, and not opinions, I contemplate with sovereign reverence 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. Certainly no power to prescribe any religious exercise, or to assume authority in religious discipline, has been delegated to the general government. It must then rest with the states as far as it can be in any human authority."
The conflict over this issue didn't enter the courtrooms until 1878, in the case of Reynolds v. United States. Reynolds argued that it was his religious duty as a Mormon to marry multiple wives, and a law prohibiting polygamy violated his First Amendment Rights.
The court cited Jefferson's letter, emphasizing the difference between religious belief and action stemming from religious belief. They argued that allowing polygamy could establish precedent so that someday someone might argue that human sacrifice was necessary for their religion, and "to permit this would be to make the professed doctrines of religious belief superior to the law of the land, and in effect to permit every citizen to become a law unto himself."
Up until the 1980s, "The Separation of Church and State" was considered as Constitutional a term as the First Amendment. In 1985, in the case of Wallace v. Jaffree, the Supreme Court ruled that forcing children to observe prayer in school was unconstitutional. Justice William Rehnquist dissented, however, arguing that the reasoning behind the Establishment Clause was flawed in that it was based on Jefferson's letter, who was not the author of the Clause.
Nevertheless, the Court ruled in favor of Wallace, holding
"Just as the right to speak and the right to refrain from speaking are complementary components of a broader concept of individual freedom of mind, so also the individual's freedom to choose his own creed is the counterpart of his right to refrain from accepting the creed established by the majority ... when the underlying principle has been examined in the crucible of litigation, the Court has unambiguously concluded that the individual freedom of conscience protected by the First Amendment embraces the right to select any religious faith or none at all."
They further held the opinion that "...The State's endorsement of prayer activities at the beginning of each school-day is not consistent with the established principle that the government must pursue a course of complete neutrality toward religion."
And that is the crux of the issue: The government must pursue a course of complete neutrality. My friend disagreed with people getting mad when they hear a legislator ruling or voting based on their religious belief. That voting based on belief was not the same as a government-established religion.
I'm okay with religion. I think it's fine that we have religious people in office. But their belief is a matter between them and their god, and as a constituent they have no right to include me in their belief. Hence the necessity of neutrality: ruling and voting in a way that will benefit everyone equally.