This is the latest book by Michael Shermer, a well-known American science writer and debunker of conspiracy theories and supernatural beliefs. I don't share Shermer's rationalistic perspective, but I liked the book.
Shermer's central thesis is simple. Human beings, like other animals, have evolved to find patterns in essentially random data and to attribute purpose and meaning to them. When applied to the rough fabric of human affairs, this generates phenomena such as conspiracy theories; when applied to the cosmos, it generates belief in a God. Confirmation bias and other cognitive glitches then do the rest, making sure that our initial intuitions continue to seem plausible to us and are protected against refutation. Once our beliefs have been formed, says Shermer, we rarely change them.
Shermer argues that much of our propensity for belief is inborn, noting that studies of identical twins suggest that our genes are responsible for up to 55% of our religiosity. He suggests that believers' brains are over-supplied with dopamine and dominated by the right hemisphere. He is honest enough to recognise that scientists too have their own cognitive limitations and are capable of being psychologically invested in their theories to an extent that goes beyond the evidence. Nor is intelligence by itself enough to protect us from going astray: clever people, he says, are unusually good at finding arguments and reasons to justify positions which they have arrived at by non-clever means.
I agree with much of this. Human beings are not rational animals, whatever Aristotle said. The psychological research on motivated reasoning, confirmation bias and other human cognitive flaws indicates that we tend to believe what we want to believe and then look for reasons to justify it. This insight can be taken too far, into a kind of postmodern relativism which begins to deny any role for objective evidence in shaping our beliefs (I commented on this in my review of Peter Hitchens' The Rage Against God), but it is true enough for much of the time.
Shermer is not dogmatically scientistic like Richard Dawkins, nor is he a refugee from the Enlightenment like A.C.Grayling. Indeed, his honesty and cynicism make a nice change from the self-satisfied rhetoric of rationality which one finds in so much atheist writing. He doesn't regard atheists as clear thinkers who have rejected superstition and unreason, and he is aware of the limits of hardline empiricism. He is candid about the non-rational, social and psychological drivers of his own de-conversion from evangelical Christianity to scepticism. He freely admits that he would like to believe in life after death - he just doesn't.
I would take issue with Shermer's wholly materialistic premises. He makes two assumptions in particular which limit his conceptual field of vision. First, he appears to assume that, if something can't be produced and reproduced on cue in a laboratory, it isn't real. He is letting himself off too lightly here. He allows himself to dismiss a huge body of data on religious and paranormal experiences as anecdotal and to avoid engaging with it. Second, he appears to think that such experiences, if they are real, must take place purely within an invisible soul or spirit. He therefore assumes that, if he can identify a physical part of the brain that is associated with an allegedly supernatural phenomenon - say, biochemical changes in the brains of meditating monks and praying priests - this means that the phenomenon can immediately be withdrawn from the realms of mysticism and claimed entirely for materialist science. This is altogether too pat, and relies on a body/soul, natural/supernatural dualism which cries out for deconstruction.
Other points might be made too. Even if one accepts all of Shermer's premises, I have serious doubts that his chosen explanatory model can explain everything that he applies it to. An evolved propensity to see significant patterns where none truly exist might explain belief in (say) political conspiracies, but it is less obvious why it would favour (say) belief in an afterlife. Moreover, the cultural biases and assumptions of modern scientists, which Shermer is happy to acknowledge, mean that the deck is stacked against those who would depart from the materialist paradigm. Trying to get a paper on, say, the evidence for psychic mediumship published is unlikely to be either an easy or a career-enhancing move for most Western academics. In similar vein, Dave Evans pointed out in Ten Years of Triumph of the Moon that "normal" psychologists are held to a statistical threshold of 0.05 for significance, while parapsychologists are required to attain a level of 0.001 to receive the same credibility.
In all, this is an interesting and varied book, and one need not accept all of its premises to be able to learn from it.