The Believing Brain: From Ghosts and Gods to Politics and Conspiracies—How We Construct Beliefs and Reinforce Them as Truths. By Michael Shermer.

But his latest book is more than just a display case full of specimens collected by a man fascinated by the paranormal. Mr Shermer is interested in how such beliefs come to be held, and why they can persist even in the face of what, to others, can seem to be the overwhelming evidence that contradicts them.

The first part of the book is a mixture of psychology and trendy neuroscience research that presents the evidence for Mr Shermer's central claim: that, instead of shaping belief around painstakingly gathered, soberly judged evidence, people most often decide upon their beliefs first, and then use an impressive range of cognitive tricks to bend whatever evidence they do discover into support for those pre-decided acts of faith.

In the second part of “The Believing Brain” Mr Shermer applies those observations to the almost infinite variety of weird and wonderful beliefs that people hold, from alien abductions to government conspiracies to bring down the World Trade Centre—and, inevitably, to religion (a chapter on politics, by contrast, feels misplaced and forced). He is an able skewerer of sloppy thinking. The section on conspiracy theories, for instance, memorably exposes the bizarre leaps of logic that adherents often make: “If I cannot explain every single minutia [about the collapse of the twin towers]…that lack of knowledge equates to direct proof that 9/11 was orchestrated by Bush, Cheney, Rumsfeld and the CIA.”

A common risk with this kind of book is that the author comes across as overly smug and superior; just look at how the duke of debunkers, Richard Dawkins, is sometimes perceived, even by his fans. Mr Shermer is aware of this risk, and is at pains to reassure readers that his conclusions apply to everyone, even himself. In a chapter on alien abductions, he recounts an abduction story of his own. Exhausted after cycling 1,259 miles in 83 hours as part of an endurance challenge called the Race Across America, he becomes convinced that the motorhome carrying his support team is actually an alien spacecraft, and that his team's pleas for him to come inside and get some rest are merely a cunning pretext to get him to co-operate with a spot of alien probing. Surprised when the interior of the mothership turns out to closely resemble a General Motors motorhome, Mr Shermer consents to lying down. On waking a couple of hours later, he is able to joke about the experience with his team-mates.

That experience gives one useful definition of a sceptic, as Mr Shermer understands the term: one who is aware of the fallibility of intuitions, and willing to take steps to minimise them. It remains, sadly, an uncommon combination.