Not unexpectedly, Christian nation advocates emphasize letters or other writings that suggest Madison was a Christian. But their emphasis on Madison’s religiosity, just like the reliance they place on the religious beliefs of Madison’s contemporaries, exposes the key fallacy of the Christian nation thesis, which is that being a Christian somehow commits one to the view that the government must be based on biblical precepts. Christian nation proponents make an inference from the premise that Madison, many of the Founders, and much of the population were Christian, to the conclusion that they must have wanted the United States to be structured as a Christian nation. Uh, … no. Fortunately, the people who established the United States did not suffer from the narrow-mindedness, lack of foresight, and ethical blindness that afflicts many Christian nation advocates. There is no contradiction in being Christian and being in favor of a secular nation. Far from it. People like Madison recognize that freedom of conscience is an important value that Christians should embrace. If Madison was a Christian, he was like many other enlightened Christians of his time; they did not want people pressured, directly or indirectly, into becoming Christians. They thought people should come to Christ of their own free will. Furthermore, they recognize that a secular state, a state that does not have the authority to meddle in religious matters, is the best guarantor of religious liberty, for Christians and for everyone else. A government that believes it has the authority to regard itself as the government of an officially Christian nation, will also think it has the authority to define what beliefs and practices are truly Christian. Some day it may also believe that is has the authority to declare itself that government of an officially Islamic nation or atheist nation.
–Ronald A. Lindsay, The Necessity of Secularism pgs 42-43