At the launch of her new book, psychologist Dorothy Rowe said she intended it to act as a sequel to The God Delusion. Dawkins, she said, had posed the question: "Why do intelligent people believe this garbage?" In What Should I Believe?, Rowe gives an answer, though with less of a blanket judgment as to the rubbishness or otherwise of the religious outlook. In fact, her explanation could be used to understand any form of belief, Dawkins' included.

She starts from the premise that our greatest fear is annihilation, not physical death, necessarily, but annihilation as a person. It is the desire to avoid this that motivates us throughout our lives. For some, religion is the answer, because it tends to suggest quite straightforwardly that life carries on after death.

But a continuation of our existence is what we all clamour for, religious or not; parents hope their worldview will shape the lives of their children; some take comfort from the fact that their "blood" or "genes" will be around after they've gone. Artists imagine the work will stand as a monument to them. Humbler people hope they'll live on, at least, in their friends' memories or through the effects of the good things they've done. To live without any hope of projecting one's soul is, Rowe argues, impossible. Test yourself, if you believe you do.

So why be the Pope rather than Picasso? Why choose religion as your balm, rather than some other route to eternal life? According to Rowe's model, that decision is the result of a kind of cost-benefit analysis for the individual – and those costs and benefits can come from absolutely anywhere within the arena of personal experience. And into the mix goes the cast of your personality – introvert or extrovert. Will my father beat me if I'm not devout? Well I had better believe then. Or not, depending on which is worse, giving in to dad or getting hit. Is it easier for me to believe that despite the dead-end job that absorbs all my time I will receive a reward in heaven, or to take the huge material risks involved in pursuing self-expression? Again, it depends.

All this presents a bit of an obstacle for those who think that the problem of religion can be "solved". When the explanation for religious belief is a question of individual psychology, there's little room for the argument that it can be educated away. There are always going to be situations where it makes (personal) sense to be a Muslim, Catholic or Hindu.

All this reminds me of Aldous Huxley, and the best book I've ever read on the psychology of religion, the Devils of Loudun. In it Huxley tells the story of the most notorious mass-possession in French history. A bunch of sexually and emotionally thwarted nuns and some jealous politicians join forces to destroy a liberal, charismatic priest, Urbain Grandier. Along the way, the drives that exist within us all manifest themselves in some particularly bizarre ways.

I say it's a book about the psychology of religion, but we could leave out the religion part. It so happened that at the time of the events at Loudun, society was ordered, nominally at least, along religious lines (in fact it was ordered like any pre-industrial socially conservative society anywhere). So the expressions of frustration, jealousy and rage were made to fit into a religious – in this case, Catholic – framework. Grandier was tortured and burnt at the stake in the name of the Catholic God. But it would be a mistake to assume that had religion not been there to justify the execution, it wouldn't have happened. Some other justification would, of course, have been found (as Arthur Miller showed by linking witch-paranoia and anti-communism – and before you counter that it wasn't as bad, remember that people were put to death as a result of the red scare). As Huxley puts it:

All the evils of religion can flourish without any belief in the supernatural … Such behaviour patterns antedate and outlive the beliefs which, at any given moment, seem to motivate them.

What do Huxley and Rowe's messages have in common? Both say: if you want to know where the trouble lies, look at the person and the reasons they have come to interpret the world in a particular way. Most critics of religion don't – they jump straight to content of the interpretation and become convinced that's the root of whatever disaster has occurred. It is a classic case of barking up the wrong tree.