Superstitions arise as the result of the spurious identification of patterns. Even pigeons are superstitious. In an experiment where food is delivered randomly, pigeons will note what they were doing when the pellet arrived, such as twirling to the left and then pecking a button, and perform the maneuver over and over until the next pellet arrives. A pigeon rain dance. The behavior is not much different than in the case of a baseball player who forgets to shave one morning, hits a home run a few hours later and then makes it a policy never to shave on game days.

Beliefs come first; reasons second. That's the insightful message of The Believing Brain, by Michael Shermer, the founder of Skeptic magazine. In the book, he brilliantly lays out what modern cognitive research has to tell us about his subject—namely, that our brains are "belief engines" that naturally "look for and find patterns" and then infuse them with meaning. These meaningful patterns form beliefs that shape our understanding of reality. Our brains tend to seek out information that confirms our beliefs, ignoring information that contradicts them. Mr. Shermer calls this "belief-dependent reality." The well-worn phrase "seeing is believing" has it backward: Our believing dictates what we're seeing.

Mr. Shermer marshals an impressive array of evidence from game theory, neuroscience and evolutionary psychology. A human ancestor hears a rustle in the grass. Is it the wind or a lion? If he assumes it's the wind and the rustling turns out to be a lion, then he's not an ancestor anymore. Since early man had only a split second to make such decisions, Mr. Shermer says, we are descendants of ancestors whose "default position is to assume that all patterns are real; that is, assume that all rustles in the grass are dangerous predators and not the wind."

In addition, as evolved social creatures, we have brains that are attuned to trying to discern the intentions of others—and we look for patterns, there, too, and then try to infuse them with human intention and meaning, or what Mr. Shermer calls "agenticity." Patterns in life are variously ascribed to the work of ghosts, gods, demons, angels, aliens, intelligent designers and federal conspirators. "Even belief that the government can impose top-down measures to rescue the economy is a form of agenticity," the author says.

Mr. Shermer also delves into the neuroscience of "the believing brain." For example, he cites research suggesting that people with high levels of the feel-good neurochemical dopamine "are more likely to find significance in coincidences and pick out meaning and patterns where there are none." Even for folks with normal chemical levels, there's a neurological upside to pattern-finding: When we come across information that confirms what we already believe, we get a rewarding jolt of dopamine.

The Believing Brain perhaps inevitably turns to religion, but a sign of Mr. Shermer's all-purpose skepticism is his consigning of the chapter "Belief in God," along with "Belief in Aliens," to a section called "Belief in Things Unseen." He doesn't take religious faith seriously except as an object for explanatory debunking—God is simply the human explanation for pattern-making and agency on an epic scale.

"As a back-of-the-envelope calculation within an order-of-magnitude accuracy, we can safely say that over the past ten thousand years of history humans have created about ten thousand different religions and about one thousand gods," Mr. Shermer writes. He lists more than a dozen gods, from Amon Ra to Zeus, and wonders how one of them can be true and the rest false. "As skeptics like to say, everyone is an atheist about these gods; some of us just go one god further."

Readers who have enjoyed Mr. Shermer's earlier books, such as Why People Believe Weird Things,* will relish the pages devoted to puncturing many of the conspiratorial beliefs that lurk in our popular culture, from those about UFO cover-ups to the 9/11-was-an-inside-job lunacy. He also recounts, apparently not for the first time, his own supposed alien-abduction experience. In 1983, competing in the Race Across America bicycle challenge, he rode 1,259 miles in 83 hours without sleep and became delirious with exhaustion. When his support crew finally intervened to make him stop and get some rest, he became convinced that they were aliens forcing him into a mother craft—the interior of the UFO, it turned out, looked "remarkably like a GMC motor home." A good long nap cured him of his delusion.

One of the book's most enjoyable discussions concerns the politics of belief. Mr. Shermer takes an entertaining look at academic research claiming to prove that conservative beliefs largely result from psychopathologies. He drolly cites survey results showing that 80 percent of professors in the humanities and social sciences describe themselves as liberals. Could these findings about psychopathological conservative political beliefs possibly be the result of the researchers' confirmation bias?

As for his own political bias, Mr. Shermer says that he's "a fiscally conservative civil libertarian." He is a fan of old-style liberalism, as in liberality of outlook, and cites The Science of Liberty author Timothy Ferris's splendid formulation: "Liberalism and science are methods, not ideologies." The "scientific solution to the political problem of oppressive governments," Mr. Shermer says, "is the tried-and-true method of spreading liberal democracy and market capitalism through the open exchange of information, products, and services across porous economic borders."

But it is science itself that Mr. Shermer most heartily embraces. The Believing Brain ends with an engaging history of astronomy that illustrates how the scientific method developed as the only reliable way for us to discover true patterns and true agents at work. Seeing through a telescope, it seems, is believing of the best kind.

*Title corrected.

Ronald Bailey is Reason's science correspondent. His most recent book, Liberation Biology: The Scientific and Moral Case for the Biotech Revolution, is available from Prometheus Books. This article originally appeared in The Wall Street Journal.