I can’t count the number of times I’ve seen atheists float the myth that Americans are more religious than Europeans because Europeans have had to live under oppressive or plain boring state churches, whereas Americans have enjoyed separation of church and state. This idea goes back to Andrew Jackson, who “explained, in refusing to name a fast day, he feared to ‘disturb the security which religion now enjoys in this country, in its complete separation from the political concerns of the General Government.'”
It was only a matter of time before someone propagated that idea on PZ’s thread about Harvard’s religion courses. QrazyQat said, “The bottom line difference is that European countries have experience with state religion,” and when I criticized him, Caledonian volunteered, “Then perhaps the difference is that European countries have had greater experience with authoritarianism than the US.”
Actually, neither of these is true. A good way of testing either of these hypotheses is by looking at European countries with experience with state religions, and European countries with experience with authoritarianism. France has had separation of church and state de jure for a century and serious clashes with the Catholic Church since the Revolution; it also has the most secular population in non-Scandinavian Western Europe. In addition, its anti-authoritarian tradition is longer than this of any other country but the US and UK.
A more instructive way to look at the situation is by comparing pairs of countries that have similar experiences with state religion and authoritarianism but different levels of religiosity. The Czech Republic is the most secular non-Scandinavian, non-East Asian nation, while Slovakia’s level of religiosity is middle of the road. Canada is fairly non-religious, while the US is more religious than any other first-world nation. Germany is mostly secular (except for Bavaria), while Austria is middle of the road.
One of the most glaring divides in the Christian world is Protestant/Catholic. The Catholic Church has retarded progress, which is why although the Renaissance began in Italy (and even then, in one of the cities farthest from Rome) and the first European superpowers were Spain and Portugal, the center of Western progress shifted north.
France is the glaring exception to that rule. And that’s because the Catholic Church has always been weaker there than in southern and eastern Europe; even before the Revolution, France could produce copious liberal intellectuals, who after the Revolution were secure from Church persecution.
But, of course, that won’t explain why the US, which is traditionally Protestant, is so religious, far more than any other Protestant country. But there’s a similar explanation, based on retardation of progress: the frontier society. Although the frontier begins as atheistic, it’s easy to turn it fundamentalist with fanatical preachers using homey soundbites.
All the churches that flourished in the South and West of the United States – the Baptists, the Methodists, and so on – were fairly low-brow. Catholics required priests to go to seminary to be allowed to spread the faith; old-world Protestants were more populist, but largely copied the same system.
In contrast, the Puritan mentality that has dominated in the US, even among secularists, says that everyone can preach the faith, as long as he is sufficiently zealous and untainted by doubt. The Catholic Church has dogma; Puritans have literal readings of the Bible. Even pseudo-intellectual study of theology has a moderating effect, especially when carried out in an institution that also trains natural philosophers who tell you your faith makes no sense.
Incidentally, just saying that the US is more religious because of the infusion of Puritans would be wrong. In 1700, the colonies weren’t more religious than England, with the obvious exception of Massachusetts. The US only became as religious as it is after a few Great Awakenings, which required a heavily populist and personal view of religion, and a religious culture emphasizing charisma more than theology.
Separation of church and state has a non-causal relationship with the USA’s religiosity, though. Like all radical movements, Puritanism is schismatic; the Catholic Church has a single Pope who tells everyone what to do, whereas Protestantism is divided, especially in the US.
The same fundamentalists who held that everyone could proselytize were also mortally afraid of competing fundamentalists and therefore requested separation of church and state. The Baptists and Evangelists used to be the most vocal proponents of separation of church and state. The reason fundamentalists oppose separation now is that centuries of conservative American theology have served to unify various churches under a pan-denominational Dominionist umbrella.
Canada isn’t an old world country, but its history is more recent than the United States’. It was under British control for 90 years more than the US was, and skipped both Great Awakenings. Further, it never had a Puritan tradition permeating its psyche; you won’t catch a Canadian politician using the phrase “shining city on the hill.”
In general, separation of church and state then doesn’t cause the people to become more or less religious. Countries with secular civic traditions like France and the US have separation of church and state; countries with religious ones like Britain don’t.
Even religious wars don’t contribute to or detract from secularism except in very specific circumstances – England became more liberal after the Civil War, but in the Thirty Years’ War, the country that was most devastated, Germany, later became more religious than its neighbors to the north and west. It all depends on the specifics – if the country is left more united, then it’ll grow more tolerant, whereas if it splinters the way Germany did, the local rulers will be able to impose religion on the inhabitants with ease.