Separation of church and state in the United States:

Jefferson and James Madison's conceptions of separation have long been debated. Jefferson refused to issue Proclamations of Thanksgiving sent to him by Congress during his presidency, though he did issue a Thanksgiving and Prayer proclamation as Governor of Virginia. Madison issued four religious proclamations while President, but vetoed two bills on the grounds they violated the first amendment. On the other hand, both Jefferson and Madison attended religious services at the Capitol. Years before the ratification of the Constitution, Madison contended "Because if Religion be exempt from the authority of the Society at large, still less can it be subject to that of the Legislative Body." After retiring from the presidency, Madison wrote of "total separation of the church from the state." " "Strongly guarded as is the separation between Religion & Govt in the Constitution of the United States," Madison wrote, and he declared, "practical distinction between Religion and Civil Government is essential to the purity of both, and as guaranteed by the Constitution of the United States." In a letter to Edward Livingston Madison further expanded, "We are teaching the world the great truth that Govts. do better without Kings & Nobles than with them. The merit will be doubled by the other lesson that Religion flourishes in greater purity, without than with the aid of Govt." Madison's original draft of the Bill of Rights had included provisions binding the States, as well as the Federal Government, from an establishment of religion, but the House did not pass them.[citation needed]

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What is essential to the purity of both religion and civil government?
practical distinction