Joseph Story is a seminal figure in American legal history. He was a member of the US Supreme Court in the early 19th Century, helped start Harvard Law School and wrote commentaries on the law that provide great weight in determining the original understanding of the American Constitution and common law. He is often cited for a conservative reading of the religion clauses, and has some quotations which, taken out of context, could support the "Christian Nation" ideal. For instance, a quotation that the late Chief Justice William Rehnquist invoked, and currently invoked by this conservative historian, informs:
The real object of the amendment was not to countenance, much less to advance, Mahometanism, or Judaism, or infidelity, by prostrating Christianity; but to exclude all rivalry among Christian sects, and to prevent any national ecclesiastical establishment which should give to a hierarchy the exclusive patronage of the national government. It thus cuts off the means of religious persecution (the vice and pest of former ages), and of the subversion of the rights of conscience in matters of religion, which had been trampled upon almost from the days of the Apostles to the present age. [Joseph Story, Commentaries on the Constitution of the United States, 5th ed. (Boston: Hilliard, Gray & Co., 1833), 701]
Story's "real object" discusses what he saw as the underlying purpose of the First Amendment. However, constitutional scholars note it's not the underlying purpose of a particular text that controls, but the original meaning of the text itself. Liberal scholars, for instance, Justices Stephen Breyer or David Souter, offer quotations from other Founders (e.g., James Madison who played a more important role than Story in passing the First Amendment) that show other underlying purposes of the First Amendment, for instance to take the religious passion out of politics by consigning religion to the private sector, or to the realm of "individual conscience" as opposed to "public policy." If "underlying purposes" controlled, Justices can (and many of them do) simply choose from a number of differing underlying purposes to suit the results they desire, offer selected quotations from Founders, and proceed to subvert the text of the Constitution itself!
But more importantly, what Story meant when he invoked "Christianity" arguably isn't Christianity, or at least not "Christianity" as the orthodox (i.e., conservative evangelicals and Catholics) understand the term. Story was, like many luminaries of the American Founding, a Unitarian. And these men like Jefferson, Adams, Franklin, Madison, Marshall, Morris, perhaps Washington, Hamilton, and Wilson, were more likely to term their creed "Christianity" than "Deism."
I would submit, it is simply not possible to give "Christianity" only rights under the religion clauses, because that would require the law to determine what is Christianity, which the doctrine of the unalienable rights of conscience forbids. According to Madison, judges or law makers would now be in the business of deciding what is orthodoxy, and what is heterodoxy, which is unacceptable. As Walter Berns put it in Making Patriots:
How could the states promote religious belief if, as Madison anticipated and as in fact was increasingly the case as the nineteenth century proceeded, they had to deal with a plurality of sects, and not all of them Christian? To be specific, how could Charles Turner expect his state of Massachusetts to provide religious instruction in its schools if its residents disagreed on the tenets of religion?
Although this is not the place to recount it, the history of American elementary education is, in one significant respect, a history of the gradual secularization of the public schools and their curricula. (p. 70).
Joseph Story apparently thought it acceptable for states to promote "Christianity" not other religions, but let us examine what Story meant by "Christianity." Here is testimony from Story's brother, speaking to and through Story's son:
After my continued absence from home for four or five years, we met again, your father being now about eighteen years old, and renewed our former affection towards each other. At this time we were, from a similarity of sentiment, drawn more closely together. I allude particularly to our religious opinions. We frequently discussed the subject of the divinity and the humanity of Christ, and we both agreed in believing in his humanity. Thus you see that your father and myself were early Unitarians, long before the doctrine was preached among us by any one, unless I except Dr. Bentley of Salem.
In other words, Story was a Socinian Unitarian, believing Jesus was 100% human and not divine at all. And here is Story's opinion on salvation:
This faith he retained during his whole life, and was ever ardent in his advocacy of the views of Liberal Christians. He was several times President of the American Unitarian Association, and was in the habit of attending its meetings and joining in its discussions. No man, however, was ever more free from a spirit of bigotry and proselytism. He gladly allowed every one freedom of belief, and claimed only that it should be a genuine conviction and not a mere theologic opinion, considering the true faith of every man to be the necessary exponent of his nature, and honoring a religious life more than a formal creed. He admitted within the pale of salvation Mahommedan and Christian, Catholic and Infidel. He believed that whatever is sincere and honest is recognized of God; — that as the views of any sect are but human opinion, susceptible of error on every side, it behooves all men to be on their guard against arrogance of belief; — and that in the sight of God it is not the truth or falsity of our views, but the spirit in which we believe, which alone is of vital consequence.
Now, however nice sounding "liberal unitarian Christianity" is, traditional Christians of the Founding era and today would assert: whatever it calls itself this is not Christianity. Call it unitarianism, call it theistic rationalism, don't call it Christianity. Joseph Story, however, was adamant that his creed deserved the label "Christian":
TO WILLIAM WILLIAMS, ESQ.
Washington, March 6th, 1824.
I acknowledge with pleasure your letter of the second of February, which reached me a very few days since. What you say of the false statements in the prints respecting Unitarians does not surprise me; for I well know that bigotry, and misapprehension, and ignorance are very like to lead men to the most extravagant opinions. The Unitarians are universally steadfast, sincere, and earnest Christians.
They all believe in the divine mission of Christ, the credibility and authenticity of the Bible, the miracles wrought by our Saviour and his apostles, and the efficacy of his precepts to lead men to salvation. They consider the Scriptures the true rule of faith, and the sure foundation of immortality. In short, their belief is as complete of the divine authority of the Scriptures, as that of any other class of Christians.
It is a most gross calumny, therefore, to accuse them of treating the Bible and its doctrines as delusions and falsehoods, or of an union with Deists. In sincere unaffected piety, they yield to no persons. They differ among themselves as to the nature of our Saviour, but they all agree that he was the special messenger of God, and that what he taught is of Divine authority. In truth, they principally differ from other Christians in disbelieving the Trinity, for they think Christ was not God, but in the Scripture language “the Son of God.”
Presumably Story, like Jefferson et al., thought his own unitarianism to be "true Christianity," and in the ideal would prefer government promote that, not orthodox Trinitarianism. To the orthodox, government might as well promote Islam, Deism or atheism, than what they regard as the soul damning heresies of unitarinaism.
Indeed, Story's son recognized this narrowness of orthodox Trinitarian Christianity (and the orthodox would point out that Jesus did say something about His way being a "narrow" path):
While in the ignorance and bigotry of the age Unitarianism was considered as nearly a convertible term with Atheism, and was scarcely avowed, he believed in the humanity of Christ, and fearlessly spoke his mind.
In other words, orthodox Trinitarian Christians, who didn't believe Unitarianism to be "real Christianity" were ignorant bigots. But in any event, according to the men who wrote and expounded upon the text of the First Amendment in the Founding era, if "Christianity" were to have any special rights or organic connection to civil government, this (what the orthodox regard as) false, heretical system of "liberal unitarian Christianity" had at least equal rights with orthodox Trinitarian Christianity. Indeed, arguably unitarianism was more important than Trinitarianism because unitarinianism more meaningfully connects to the ideas of America's Declaration and Constitution than does orthodox Trinitarianism.
As Gregg Frazer noted, freedom of religion as a doctrine meaningfully connects with unitarianism or as he terms it "theistic rationalism."
It is difficult for those who believe in the importance of fundamental doctrines and a specific road to Heaven (for example, the Puritans in seventeenth-century New England) to allow "false" and "blasphemous" religions to be practiced within their sphere of authority. For the theistic rationalists, however, what was really important was not the flourishing of religious truth, but the flourishing of morality and society. Since they held to no particular creed but "essentials" to which "all good men" could agree, they had a profound indifference toward specific sects and doctrines. (PhD thesis, at 417-18).
Indeed, the text of the federal religion clauses gives rights to "religion" not Christianity. And accordingly, the original meaning of the Constitution protects "religion" in general, not Christianity in particular. (And remember, it's the text, not the intent that controls.) This itself evidences unitarianism's influence. Gregg Frazer asks, "did the Founders actually, in a sense, 'establish' their own religion of theistic rationalism?" (Id., p. 419). Frazer quotes Thomas Pangle who noted Jefferson's "real goal" was "conformity based on indifference; not diversity, but the tepid and thoughtless uniformity of Unitarianism in a society where Unitarians no longer have to defend and prove themselves." (Id., p. 420). Cushing Strout likewise wondered: "The conundrum that Jefferson and Madison left to posterity was one they never appreciated: did their policy...seek to 'establish' their own 'enlightened' religion under the guise of 'disestablishment'?" (Id.).
So in the end, there is not much of a meaningful difference between "exclud[ing] all rivalry among Christian sects" as Joseph Story saw it or excluding rivalry among all religious sects, as Madison, Jefferson and the other key Founders saw it. The bottom line is the Constitution protects "religion" not "Christianity." And that in essence is a quasi-secular policy. Judaism, Islam, Hinduism and Deism take their fundamental rights, under America's Constitutional system, equally with Christianity.