New insight has been found concerning the religious beliefs of James Madison, maybe this information is common knowledge, but let Mr. Madison's words speak for himself; in no way was Mr. Madison a rationalist, the evidence from his Memorial and Remonstrance in 1785, without any other quotes from him supporting heterodoxy prior to 1785, he must be considered an orthodox Christian, or at the least, a unitarian. Without any quote from Madison regarding Socianism, Arianism, or Unitarianism that I have overlooked, the evidence from the Memorial support his orthodoxy. Let James Madison speak for himself:
"All civilized societies would be divided into different sects, factions...the disciples of this religious sect or that religious sect. In all cases where a majority are united by a common interest or passion, the rights of the minority are in danger. What motives are to restrain them? A prudent regard to the maxim, that honesty is the best policy, is found by experience to be as little regarded by bodies of men as by individuals. Respect for character is always diminished in proportion to the number among whom the blame or praise is to be divided. Conscience, the only remaining tie, is known to be inadequate in individuals; in large numbers, little is to be expected from it. Besides, religion itself, may become a motive to persecution and oppression." James Madison, June 6, 1787. Journal of the Federal Convention by Madison.
Madison is saying reason is insufficient as the primary revelation of truth, thus eliminating the rationalist label put upon him. To Madison, man's reason was insufficient to be ultimate truth, yet alone, to base religion or morality upon. Madison defers to religion because the correct religion is obviously superior to reason; a substitute for the conscience, and this religion is the "light of revelation" he speaks about in his Memorial. He then, claims even religion, can be perverted, as its past abuses show. Madison then claims his belief of the remedy is Republicanism by God's Law:
"The only remedy is, to enlarge the sphere, and thereby divide the community into so great a number of interests and parties, that, in the first place, a majority will not be likely, at the same moment, to have a common interest separate from that of the whole, or of the minority; and in the second place, that in case they should have such an interest, they may not be so apt to unite in the pursuit of it. It was incumbent on us, then, to try this remedy, and, with that view, to frame a republican system on such a scale, and in such a form, as will control all the evils which have been experienced." Madison, June 6, 1788. Elliot's Debates In the Several State Conventions on the Adoption of the Federal Constitution(Virginia).
Not only was Madison orthodox in his beliefs in Christianity, included in that orthodoxy he believed in was original sin, evidenced by all his references about the evil of man, and Republicanism as a partial remedy. There is no partial depravity in man, man is a sinner or he isn't. Of course man can be good, but this is common sense. Madison again on the depravity of man, which he believed in from his childhood to the orthodox teaching he received at Princeton:
"If angels were to govern men, neither external nor internal controls on government would be necessary. In framing a government which is to be administered by men over men, the great difficulty lies in this: you must first enable the government to control the governed; and in the next place oblige it to control itself." Federalist #51.
The internal control over man he speaks of is to halt the depravity of man, which he believed in. Only until he became a polytheist did he become a clear arminian.
From these statements, we know Madison believed Republicanism was designed to limit sin, as much as possible, which Madison believed was the reason for a separation of powers in a Republican Government. As you can see, while Madison helped form the nation, he concurred with Montesquieu, that the separation of powers doctrine is a part of the only true religion, Christianity, and Jeremiah 17:9 is inherent in it, "The heart is deceitful above all things, and desperately wicked: who can know it?"
The sum of this matter, which has been speculated on for years, is, unless new insights into Madison's words are revealed, that James Madison was an orthodox Christian; his notes referring to "what is christianity" by itself, does not support him being heterodox, but only that he thought those sects were Christian. It seems at this point in his life, he held the same views as fellow framer, Benjamin Rush, which were orthodox views on the essentials of Christianity.
Madison's departure from these essentials happened after he helped form the nation, as I earlier noted. What is clear, so far, is James Madison was no rationalist, or theistic rationalist. He believed man's reason was insufficient for determining truth, because man's reason is flawed and can never be trusted to be superior to God's word, which is direct, rather than unreliable like our conscience. To believe man's flawed reason is superior to a direct revelation from God, is the height of foolishness. Even in large numbers, Madison believed man's reason was flawed, because a written law is not employed. Only Republicanism, of God's Law is sufficient.