A few days ago, for no particular reason, I was thinking about religious denominations—not whether their beliefs were true (I'm an atheist) but to what degree the members believed them, as demonstrated by the degree to which their membership affected their beliefs.
My first case was mainline Protestantism. As best I can tell, in the U.S. in my lifetime, mainline Protestants believed pretty much the same things those people would have believed if they had not been mainline Protestants, the same things college professors and elite media such as the New York Times believed. They were for decolonization, for the War on Poverty, for the Civil Rights movement, against apartheid, ... . Off hand, I cannot think of a single issue on which the dominant position of mainline Protestants was sharply divergent from the position of people of otherwise similar backgrounds who happened to be non-religious Jews, or atheists, or ... . Perhaps a reader can offer an example.
Contrast to that Catholics. Early in the 20th century, the Catholic church was the one major holdout against the eugenics movement, the project of keeping the unfit, or less fit, from reproducing, a project whose support ranged from George Bernard Shaw to Winston Churchill. In my lifetime, it has opposed contraception and abortion. It has not yet, so far as I can tell, come to terms with the now widespread acceptance of casual sex.
For a third case, a little harder to classify, consider Protestant fundamentalists, again in the U.S. in my lifetime. At first glance, they seem to fit the Catholic pattern, rejecting a good deal that the American elite accepts. But there are two qualifications worth making.
The first is that, unlike the (current) Catholics, a significant part of what they reject is modern science, in particular the theory of evolution, which underlies quite a lot of modern biology. The Catholics, in contrast, long ago abandoned any attempt at biblical chronology, accepting evolution as a scientific account while retaining their belief in God's guiding hand—a hard claim to refute.
The second is that my original criterion was not whether people believed what the elite believed but whether they believed what they would have believed absent their religion. For the mainline Protestants, given their typical cultural and professional backgrounds—especially, I think, the backgrounds of their leadership—those are pretty much the same question. But the base of fundamentalist Protestantism, at least so far as I can tell, is much more heavily weighted towards small town, rural populations, people that would be skeptical of the beliefs of the New York Times and Harvard professors whatever their religion was. It is not clear to me to what degree the beliefs of people with that background who happen to be fundamentalists are different from the beliefs of their neighbors who are not.
All of this is, of course, speculation, and not terribly well informed speculation. But it does seem to me that different religions, now and in the past, project very different images so far as how substantial their content is, how important a role it plays in the beliefs of adherents.
As Orwell put it:
Now, I find it very rare to meet anyone, of whatever background, who admits to believing in personal immortality. Still, I think it quite likely that if you asked everyone the question and put pencil and paper in hands, a fairly large number (I am not so free with my percentages as Mr. Dark) would admit the possibility that after death there might be ‘something’. The point Mr. Dark has missed is that the belief, such as it is, hasn't the actuality it had for our forefathers. Never, literally never in recent years, have I met anyone who gave me the impression of believing in the next world as firmly as he believed in the existence of, for instance, Australia. Belief in the next world does not influence conduct as it would if it were genuine. With that endless existence beyond death to look forward to, how trivial our lives here would seem! Most Christians profess to believe in Hell. Yet have you ever met a Christian who seemed as afraid of Hell as he was of cancer?