While Judge Amy Barrett awaits Senate confirmation as a Justice of the Supreme Court, there has been a drumbeat of editorials attacking her as a threat to the separation of church and state. This is not, of course, because of anything she has said. As a fact-check piece in USA Today noted, the judge has "never publicly said that she opposes the separation of church and state." And in writing about Catholic judges, she has said that "judges cannot—nor should they try to—align our legal system with the Church's moral teaching whenever the two diverge." Nonetheless, the ugly beat goes on—raising anxieties about the separation of church and state merely because Barrett is a devout Catholic.
Of course, those who bang on this drum are usually quite sincere. They really believe that the "separation of church and state" is the Constitution's principle of religious liberty. But it is not. Does the phrase bear even remote resemblance to the First Amendment's guarantee that "Congress shall make no law respecting an establishment of religion?" Not really. The only overlapping word is "of."
So why do Barrett's critics assume that separation of church and state is the Constitution's principle of religious liberty? And why do they berate the judicial nominee with this idea on account of her Catholicism? The answers lie in a history of theological prejudice.
Jefferson
The sordid story begins with Thomas Jefferson. This most philosophical of presidents and his intellectual allies tended to be theologically liberal. That is, they were suspicious of the authority claimed for relatively orthodox churches—and their clergy, creeds and dogmas—on the theory that authoritative religious claims stultified the minds of individuals in both religion and politics. This was what Jefferson meant when he declared that he had "sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man."
On the basis of such assumptions about the danger from churches, Jefferson and some of his supporters in the 1800 presidential election urged a separation of church and state. Federalist New England ministers, who were relatively orthodox Calvinists, vehemently denounced Jefferson as a deist and slaveholder and declared that the nation would be punished for these sins. Having difficulty responding to these charges on the merits, Jefferson's supporters used the idea of separation of church and state to suggest that churches and their minsters should not intrude their ideas into politics.
Of course, Jefferson's supporters did not protest when ministers spoke on behalf of Jefferson. But when Federalist ministers preached against Jefferson, his advocates condemned any mixing of religion with politics. And in 1802, in his famous letter to the Danbury Baptist Association, Jefferson adopted such rhetoric to interpret the First Amendment, saying that it established a "wall of separation between church and state." Although the letter is widely understood as a statement of religious liberty, it actually repeated a campaign theme designed to attack relatively orthodox clerical critics.
Separation of church and state thus entered American politics as a theological campaign slogan. It was a means by which Jefferson and his allies delegitimized the political speech of theologically orthodox clergy—a slogan by which they pressured theological opponents to suppress their political speech against Jefferson. Fortunately, many of them continued to speak out against slavery, thereby laying the foundation for the anti-slavery movement.
Nativists
The idea of separation enjoyed some popularity among Jacksonians, but it was mid-19th century nativists who made it popular. They despised and feared the Catholic Church and its immigrant adherents, and employed theologically liberal tropes to oppose it. It is therefore unsurprising that they summarized their approach to Catholicism with the principle of separation of church and state. As a practical matter, this tended to mean excluding Catholics and their speech from public life—for example, by trying to bar Catholics from public office, including judicial office.
For over a century, beginning in the 1840s, nativist organizations assiduously promoted the idea that the Constitution called for the separation of church and state. They denounced anyone who disagreed as un-American.

By the middle of the 20th century, their theological slogan had largely obscured the Constitution's careful language about religion—displacing it with a crude idea designed to give crude expression to even cruder prejudices. It represented a particularly ugly side of the "living Constitution."
The Constitution's language dealing with religion limits only government, barring it from establishing a religion. In contrast, the nativist slogan about separation equally limits both government and religion—indeed, it takes special aim at churches and their adherents. Even today, it continues to give perfect expression to underlying theological prejudice against orthodox religion—the sort of religion that recognizes the authority of churches or other religious organizations.
And of course, nativists took the separation of church and state seriously when it came to the judiciary. They protested against Catholic judges on the theory that they would be controlled by their faith—as if they, more than others, were apt to be captured by their precommitments. Stirring up such prejudices in 1914, the Rev. George Rutledge of Columbus urged in his Center-Shots at Rome: "Count the Catholics on the bench and at the head of departments in Ohio—number them one by one." In the same year, a New York masonic publication called Political Romanism protested that "the Chief Justice of the United States is a Catholic and therefore is coerced in the exercise of his duties." Sadly, this rhetoric is not dead—as evident from Senator Dianne Feinstein's 2017 comment to Barrett: "The dogma lives loudly within you."
The Ku Klux Klan
Lest you underestimate the perniciousness of the campaign to substitute the separation of church and state for the religious liberty promised by the First Amendment, consider that in the first half of the 20th century, the most politically powerful advocate of the separation of church was the Ku Klux Klan. Yes, the Klan. The one that flourished across much of America in the 1920s.
Though the Klan was profoundly racist, it was also theologically prejudiced. It was a theologically liberal nativist organization openly devoted to the separation of church and state. Imperial Wizard Hiram Evans, for example, demanded separation as one of the "Liberal principles" in his campaign for a "Liberal awakening," which in opposition to Catholicism, he thought would be supported by "Liberal-minded Americans."
Separation of church and state was one of the Klan's leading principles. An "authoritative" Klan writer explained in 1923 that the Klan is "pledged to maintain inviolate and perpetuate forever the principle of complete separation of Church and State." The Klan's recruiting cards listed "The separation of church and state" among its principles.
The Klan was in some ways akin to a church, and in its Klansman's Creed members recited, "I believe in the eternal Separation of Church and State." Likewise, the Women of the Nebraska Klan—an affiliate of the men's order—held discussion groups on separation. A national affiliate, the Women of the Ku Klux Klan, ritualistically placed a symbol of separation on their masonic-style altar, very nearly worshipping the separation of church and state.
Together with other nativist organizations, the Klan effectively rewrote the First Amendment. Though the amendment's words remained unchanged, large numbers of Americans—even those who were not nativists—were led to believe that the First Amendment was designed to separate church and state. The very provision that was designed to keep religious prejudice out of the Constitution was reinterpreted in terms that enforce such prejudice, giving the First Amendment a slant against orthodoxies of all sorts and especially against Catholicism.
Indeed, Supreme Court Justice Hugo Black effectively wrote separation of church and state into the First Amendment. His robes had once been white—as a leading officer of the largest klavern in Alabama. You have seen the old glossy photographs—the ones that show hundreds of robed men at night, darkly illuminated by vast burning crosses. Black was the Kladd of his kavern—the officer who administered the oath of allegiance to the assembled throngs joining the Invisible Empire. Following Black's instructions, they recited (with pauses indicated by dashes): "I swear that I will most zealously --- and valiantly --- shield and preserve --- by any and all --- justifiable means and methods --- the sacred constitutional rights --- and privileges of --- free public schools --- free speech --- free press --- separation of church and state --- liberty --- white supremacy" and so forth.
Judging Judge Barrett
Whatever you think about Judge Barrett, you might hesitate before denouncing her as a threat to the separation of church and state. Of course, there may be defensible justifications for what looks indefensible. But look before you leap.
A heritage of theological prejudice, nativism and the KKK may not be what you want to embrace. Of course, you might protest that separation of church and state has its virtues notwithstanding its ugly history, and perhaps that is a good point. But probably not. The slogan rewrites the Constitution to introduce theological discrimination against religiously orthodox Americans and, in particular, against the Catholic Church. Perhaps that's how you roll. But be prepared for your fellow Americans to wonder at your prejudice and discrimination.
Philip Hamburger is the Maurice and Hilda Friedman Professor Law at Columbia Law School, President of the New Civil Liberties Alliance, and the author of Separation of Church and State (Harvard Univ. Press 2002).
The views expressed in this article are the writer's own.