But in reacting to to separationism, many conservatives have gone overboard and are actually speaking against the separation of church and state. ¶ One example is the common arguments heard from the Religious Right that the separation of church and state is a "myth," that it was "not in the Constitution," and that it was an invention of Jefferson’s through his reference to a "wall of separation" in his letter to the Danbury Baptists in 1802. A Republican congresswoman recently denounced the separation of church and state as a "lie." ¶ This argument is both wrong and foolish. The phrase is not in the Constitution, but the principle most certainly is. More important, both the framers and almost all Americans — certainly all Protestants — viewed the provision as principled and positive.
… Christian conservatives who are hesitant about the notion today should remember that the "separation" was originally a distinction rather than a divorce. Separation was not simply negative, a reaction to the evils and excesses of Constantine’s hijacking of the mantle of the church. It was positive, a flower whose seed goes back to early American Baptists such as Roger Williams, who was the first to speak of "a wall of separation," and far earlier still to the teaching of Jesus about the different duties owed to "God" and to "Caesar," and then to a key succession of events and statements: the separation between emperor and pope when the emperor moved to Constantinople, the Fourth Treatise of Pope Gelasius in the fifth century (God "has separated the two offices for the time that followed, so that neither shall become proud"), and later the clash between Pope Gregory VII and the Holy Roman Emperor Henry IV in the eleventh century.
In short, long before Jefferson and Madison spoke and wrote, the separation of church and state and its corollary of modern institutional pluralism had their beginnings in ideas that are basic to the Jewish and Christian faiths, though so far yet to be embraced by the other monotheistic faith, Islam.