Surprised when the interior of the mothership turns out to closely resemble a General Motors motorhome, Mr Shermer consents to lying down.

ECONOMIST: A medley of aliens and conspiracy theories

Mr Shermer is aware of this risk, and is at pains to reassure readers that his conclusions apply to everyone, even himself.

ECONOMIST: A medley of aliens and conspiracy theories

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.

ECONOMIST: A medley of aliens and conspiracy theories

"As they say, nature abhors a vacuum, and the mind abhors chance, " says Michael Shermer, executive director of the Skeptics Society and author of "The Believing Brain, " a book on how humans seem hardwired to find patterns in disparate facts and unconnected, often innocent coincidences.

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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.

ECONOMIST: A medley of aliens and conspiracy theories