Upon further reflection, I’ve decided that all of that other stuff (parts 1, 2, and 3) is probably small potatoes and the biggest, most important thing driving the surge in atheism is information technology/mass media bringing people into contact with millions of other people.
Since religious belief is probably driven by some kind of neural feedback loop that basically results in people doing whatever the majority of people around them are doing, if you live in a world where everyone you talk to is Catholic, you’ll probably be Catholic, but if you suddenly switch to a world where you are watching TV and movies and talking to people on FB and Twitter and whatnot and some of them are Catholic and some are Protestant and you can even follow the Dalai Lama’s FB feed, suddenly you aren’t surrounded by Catholics anymore. Now your feedback loops cannot pick out any dominant religion for you to follow, and without the belief-experience feedback loops going on, you start to feel nothing at all.
In other words, all of those crazy Christians who homeschool their kids and refuse to let them watch TV because they don’t want them exposed to the sinful, fallen world are actually correct. Being around godless atheists all day will turn their kids into godless atheists. Except their kids grow up and join the world anyway, so it’s not really a great strategy.
Anyway, back on track: Once upon a time (about 70 years ago,) most people (at home and abroad!) got the vast majority of their functional information about the world from their parents and other members of their immediate community. We call this vertical transmission. With most of the people in a community adhering to a single religion, people were religious.
Since then, the rise of mass media communication has massively increased the amount of information people get horizontally (or laterally.) This brings people into massive numbers of people not from their own communities–thus all meme-plexes that were passed vertically through communities are under intense, novel competition from horizontally passed meme-plexes.
So Ireland, once an overwhelmingly Catholic country that rejected divorce back in 1987, just legalized gay marriage. Why? Because atheism has suddenly completely triumphed in the past 30 years–probably because the Irish started interacting with a bunch of people who weren’t Catholic via the internet.
(Hilariously, though, “Closer to Dublin, British-ruled Northern Ireland has refused to join the rest of the United Kingdom in recognizing same-sex marriage. …the majority right-wing Protestant Democratic Unionist Party, to which he still belongs, voted down same-sex marriage in the Northern Ireland Assembly for the fourth time in three years.
Much of the opposition there is rooted in religious convictions, based in evangelical Protestantism. The Catholic nationalist Sinn Fein party supports gay marriage in Northern Ireland, but has not been able to overcome the opposition.”–from the NY Times.)
Note that this does not mean that the modern meme-plexes (ie, Progressivism,) that are succeeding at horizontal transmission are “better”, more moral, or in humanity’s or your personal self-interest. It means that this particular environment (mass media/information) favors meme-plexes that are optimized for horizontal transmission over meme-plexes that are optimized for vertical transmission, and religion happens to be (in most cases) optimized for vertical transmission.