Washington, Franklin, Jefferson, Madison, Adams, Hamilton, Paine and yes, Mason were Deists. It was a very popular religion during the Enlightenment. All of those men, save Franklin, had to formally become members of the Christian denomination that was favored in their home Colony in order to hold public office. Jefferson was quite outspoken about his disbelief in Christianity yet he joined a church. It seems more realistic that Mason and the other writers of the Amendments were actually interested in protecting people from the enforced Christianity they had suffered.