Why can't we all just get along? Because the laws of physics forbid it.

The Boston Globe recently published an interesting story about how facts backfire:

It’s one of the great assumptions underlying modern democracy that an informed citizenry is preferable to an uninformed one. ... This notion, carried down through the years, underlies everything from humble political pamphlets to presidential debates to the very notion of a free press. Mankind may be crooked timber, as Kant put it, uniquely susceptible to ignorance and misinformation, but it’s an article of faith that knowledge is the best remedy. If people are furnished with the facts, they will be clearer thinkers and better citizens. If they are ignorant, facts will enlighten them. If they are mistaken, facts will set them straight.

In the end, truth will out. Won’t it?

Maybe not. Recently, a few political scientists have begun to discover a human tendency deeply discouraging to anyone with faith in the power of information. It’s this: Facts don’t necessarily have the power to change our minds. In fact, quite the opposite. In a series of studies in 2005 and 2006, researchers at the University of Michigan found that when misinformed people, particularly political partisans, were exposed to corrected facts in news stories, they rarely changed their minds. In fact, they often became even more strongly set in their beliefs. Facts, they found, were not curing misinformation. Like an underpowered antibiotic, facts could actually make misinformation even stronger.

What is surprising to me is not so much that facts cause people to become more entrenched in their beliefs -- whatever those might happen to be -- but rather how hard it is to convince people who claim to hew to the facts that this is so. The idea that more faithful adherence to objective fact will cause people's views to converge is supported by neither theory nor observation, but rather by a blind faith that Truth Will Prevail somehow.

To be sure there are circumstances where objective metaphysical truth can be very useful with respect to certain measures of utility. If you're trying to build a bridge, for example, you'll probably have better luck if you do the math than if you pray. But if you're trying to, for example, mobilize a large group of people to work together towards a common goal, you might do better by promulgating ideas that are not scientifically demonstrable (or, more to the point, falsifiable), like the idea that you are anointed by God.

But, counter the Hitchenses and the Dawkinses and the Harrises of the world, if you base your actions on a fiction then, being unconstrained by objective reality, anything is permissible, and all manner of evils predictably result: Slavery. Oppression of women. War. (It is, not coincidentally, ironic and revealing that this is exactly the same critique that is raised by the other side of the debate: if you are unconstrained by the Word of God then anything goes.)

And yet even a moment's reflection will reveal the flaw in this reasoning. It is simply not the case that "anything goes" in fiction. I cannot, for example, simply stand up on a soap box in the town square and proclaim myself to be anointed by God and expect anyone to take me seriously. The promulgation of ideas proceeds according to the laws of physics no less than the promulgation of genes. That the laws of the promulgation of ideas are not as widely known or as well understood does not change the fact that they are, in fact, in effect.

Ideas are information, and so they propagate by processes that are by now pretty well understood. Because they propagate by making copies of themselves, and because the resources required to make those copies are limited, they are subject to the laws of Darwinian evolution: ideas that are better at copying themselves make more copies and so are more likely to propagate. Being objectively true might offer a competitive advantage in some situations, but there is nothing fundamental about "truth" that makes it any more likely to propagate than fiction.

Consider the Shakers. The Shakers were a religious sect that, among other things, preached celibacy not just for priests but for everyone. Universal celibacy is not an idea that reproduces well. By way of contrast, the idea that one should be fruitful and multiply, and that abortion and contraception are evil, is an idea that reproduces extremely well. So it should come as no surprise that there are more Catholics and Mormons in the world than Shakers.

The relationship between ideas and their ecosystem (human brains and information-storing artifacts like books and computers) is an extremely complex symbiotic relationship. Ideas cannot exist without human brains to "live" in, and some ideas (like antibiotics) in turn provide benefits to brains. But sometimes -- and this is crucial -- the interests of brains and ideas are in conflict. For example, a brain that came to understand enough about objective reality might figure out how to have sex without producing offspring. The ideas resident in such a brain would then be deprived of one of their chief means of reproduction, namely, the ability to transfer into the pliable neural networks of newly formed brains that are captive audiences to their parents. On the other hand, the ideas resident in such brains might have access to other means of reproduction that would not otherwise have been available to them, like the Internet. But the fate of the idea that one should exercise conscious control over one's biological reproduction will ultimately be decided by evolution, not deliberation.

There is one aspect of the complex interplay between brains and ideas that ought to be deeply worrisome to anyone who values rationality: it is not necessary for a brain or an idea to be rational in order to benefit from the fruits of rationality. Antibiotics work equally well whether or not you believe in evolution. The Internet is equally accessible to the scientist as to the religious fanatic. As long as this is so, rationality will to a certain extent be self-undermining because the indiscriminate proliferation of the products of rationality helps irrationality to reproduce.

Viewed in this way it is no surprise that ideas become entrenched in brains in ways that make them impervious to facts. It's a defense mechanism. Ideas that resist facts have, all else being equal, a reproductive advantage over ideas that yield to them. It is dismaying how hard it is to get otherwise intelligent people to understand this. But it is not at all surprising.