Why do an overwhelming percentage of people believe in a supernatural god? It's not as though there aren't good scientific explanations for how we came to be and why most events occur. According to a bold new theory, humans are religious because religion is an accidental byproduct of our cognitive evolution, and we're therefore predisposed to believe in religion in the face of enormous amounts of evidence to the contrary. "The issue isn't the presence of evidence," Paul Bloom, the Yale psychologist who developed the theory, tells Gelf over email. "There is already plenty of evidence, say, for natural selection, and it's understandable by any high school student."

In the December Atlantic Monthly (sadly, reading the entire article online requires a subscription), Bloom describes why he believes our brains are programmed to neglect this evidence. First and foremost, he writes, people intuitively dissociate their bodies from their souls and the brain becomes, as Steven Pinker states, "a pocket PC for the soul." Bloom points to recent studies showing that most children believe that once sentient beings are dead, they still have thoughts and desires. According to Bloom, these beliefs are strongest among the youngest children, and diminish as we get older, suggesting that "the notion of life after death is not learned at all."

But a notion of the afterlife is just one aspect of most religions. A belief in Creationism, or intentional design, is another fundamental point, and Bloom describes several studies that show that we intuitively assign agency to randomness, and are predisposed to believe that there are motives behind every event. According to Bloom, our "common sense" dictates that even in the face of opposing scientific facts, we feel the need to assign agency. "People are very unwilling to give up on common sense," he tells Gelf. This belief in agency is also innate. Children—even those of atheist parents—are more likely to invoke an intentional creator in describing our origins than adults.

According to Bloom, our beliefs in the afterlife and a creator are instinctive, and have somehow converged over the course of evolution to make humans, as a group, religious beings. Interestingly, he tells Gelf that he does not expect that his scientific explanation of where religious thoughts come from will have any influence on people who are religious. "The question of where religious beliefs come from is logically separate from the question of whether such beliefs are true," Bloom says. "So someone could entirely believe in my theory of why people believe in God, for instance, and at the same time fully believe that God is real."