I worry about superstition. Rational Optimists spend much of their energy debunking the charlatans who peddle false reasons to worry. So what worries me most are the people who make others worry about the wrong things, the people who harness the human capacity for superstition and panic to scare us into doing stupid things: banning genetically modified foods, teaching children that the earth is 6,000 years old, preventing the education of girls, erecting barriers against immigrants or free trade, preventing fossil fuels taking the pressure off rain forest—that sort of thing.
Superstition can help bring down whole civilisations. As Rome collapsed, or in the Ming Empire or under the Abbasid Caliphate, the triumph of faith over reason played a large part in turning relative into absolute decline in living standards. By faith, I mean argument from authority.
There is a particular reason to worry that superstition is on the rise today—a demographic reason. As Eric Kaufmann documents in his book Shall the Religious Inherit the Earth?, the fundamentalists are breeding at a faster rate than the moderates within all the main religious sects: Sunni, Shia, Jewish, Catholic, Protestant, Mormon, Amish. The differential is great and growing.
Fortunately children do not always do what their parents tell them. Millions of indoctrinated fundamentalist children will rebel against their faiths and embrace reason and liberty, especially in the age of the Internet, mobile telephony and social networks. But there's another demographic trend: the declining global birth rate, with the number of children per woman plummeting to 2 or less in more and more countries. In a world with generally high birth rates, a breeding frenzy among fundamentalists would not matter much; but in a world with low birth rates, the effect could be startling. If secular folk don't breed while superstitious ones do, the latter will soon dominate.
It is not just religious superstition that bothers me. Scientific superstition seems to be on the rise, too, though not because of demography. Science as an institution, as opposed to a philosophy, has long had a tendency to drift towards faith—argument from authority—as well. Consider the example of eugenics in the first half of the last century, or of Lysenkoism in the Soviet Union, or Freudianism, or of the obsession with dietary fat that brooked no dissent in the 1970s and 1980s. Dissidents and moderates are all too often crowded out by fundamentalists when science gets political. Fortunately, science has a self-correcting tendency because it is dispersed among different and competing centers. Dread the day when science becomes centralised.