Now and then, scientists tout an idea so crushingly obvious that I assume I'm missing something. Case in point: the anthropic principle, which proclaims that reality has to be as we observe it to be because otherwise we wouldn't be here to observe it. I've always been baffled as to why smart people, like Stephen Hawking, take this tautology seriously.

I had a similar reaction, at first, to "argumentative theory," a trendy new explanation of why human reason so often leads people astray. The cognitive psychologists Hugo Mercier of the University of Pennsylvania and Dan Sperber of the Jean Nicod Institute in Paris assert that our reasoning ability, like speech and other cognitive tools, evolved back in the Stone Age, and natural selection favored reasoning not for solitary truth-seeking but for arguing with others. In other words, Og, our primordial forefather, would enjoy more, ahem, reproductive success by persuading his band mates that he's right—Chew a horny toad and your mate will bear you a son!—than by actually being right. We, Og's ancestors, share his "confirmation bias," the tendency to concoct as much evidence or pseudo-evidence as possible for our points of view and to ignore contrary evidence.

"Skilled arguers," Mercier and Sperber contend in a recent article in Behavioral and Brain Sciences, "are not after the truth but after arguments supporting their views." When we argue with each other the clash of viewpoints can lead to something approximating truth; hence the effectiveness of democratic governance, the adversarial legal system and science. But we may also end up believing in geocentrism, penis envy, string theory, parallel universes and gigantic earthquakes that split the planet open so dead people can fly to heaven. (These are my examples, not those of Sperber and Mercier.)

My initial reaction to argumentative theory was that it's just a truism dressed up in cognitive-Darwinian lingo. Don't we all intuit in grade school that parents, teachers and preachers are telling us things—God loves you! Liver is good for you! Americans are the best people in the world!—that might not be true? We figure out that people often try to rationalize beliefs that they adhere to for emotional, arational reasons Once we recognize this tendency in ourselves we might reject religion and become agnostic science journalists who soon learn that even world-famous scientists often succumb to confirmation bias.

Some smart people are nonetheless impressed by argumentative theory. The science impresario and book agent John Brockman highlighted it on his Web site, The journalists Chris Mooney, Sharon Begley and Jonah Lehrer have touted the work of Sperber and Mercier, as have the psychologists Steven Pinker of Harvard University and Jonathan Haidt of the University of Virginia. Haidt calls Mercier and Sperber's theory "powerful" and Pinker agrees that it is "original and provocative."

I suspect that some folks like argumentative theory less because of its intrinsic merits than because it appeals to their intellectual biases, just as the theory might predict. For example, Sperber and Mercier explain the idea in terms of evolutionary psychology, which excels at packaging cliches—Guys are more promiscuous than gals because guys don't get pregnant!—as deep insights into human nature. Hence scientists like Pinker and Haidt, who employ evolutionary explanations themselves, may favor argumentative theory out of loyalty to their much-maligned field.

Jonah Lehrer seems to like argumentative theory because it bolsters his postmodern view of science. And the theory provides a handy way for journalists like Begley and Mooney to explain why so many people stubbornly refuse to believe in human-induced global warming, the theory of evolution and other obviously true propositions. In fact, anyone can utilize argumentative theory in this way. When confronted by someone who refuses to accept your point of view, you can just shrug, shake your head and say, "You're not rational, you're argumentative."

After much reflection, I've decided that I like argumentative theory, too, for a couple of reasons: First, my objections to it stem in part from my own bias—which I admit may not be entirely rational—against evolutionary psychology and other genetically oriented approaches to human behavior. Second, and more importantly, argumentative theory—if it becomes widely discussed—may help us recognize our own biases as well as those of others. History demonstrates that certainty on the political left or right, among scientists as well as religious fundamentalists, can lead to trouble. Anything that promotes self-doubt, as argumentative theory should, can't be all bad.

But I still think the anthropic principle is a dumb idea.

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