I want to examine that dangerous thing common to Judaism and Christianity as well as the process of non-thinking called ‘faith’.

I’m a scientist and I believe there is a profound contradiction between science and religious belief. There is no well demonstrated reason to believe in God, and I think the idea of a divine creator belittles the elegant reality of the universe. The 21st century should be an age of reason, yet irrational militant faith is back on the march. Religious extremism is implicated in the world’s most bitter and unending conflicts. In Britain, even as we live in the shadow of holy terror, our government wants to restrict our freedom to criticise religion. Science we are told should not tread on the toes of theology. But why should scientists tiptoe respectfully away? The time has come for people of reason to say, enough is enough. Religious faith discourages independent thought: it’s divisive and it’s dangerous. Isn’t this the beginning of that slippery slope that leads to young men with rucksack bombs on the tube?

If you want to experience the medieval rituals of faith nobody does it better than the Catholics. At Lourdes in southern France the assault on the senses appeals to us not to think, not to doubt, not to probe. And if we can retain our faith against the evidence in the teeth of reality, the more virtuous we are.

People like to say that faith and science can live together side by side but I don’t think they can. Science is a discipline of investigation and constructive doubt, questing with logic, evidence and reason to draw conclusions. Faith by stark contrast demands a positive suspension of critical faculties. Science proceeds by setting up hypothesises, ideas, or models and then attempts to disprove them. Religion is about turning untested belief into unshakeable truth through the power of institutions and the passage of time.

Let me give you an example of this with the story of the assumption of Mary. Catholics believe that Jesus’s mother, Mary, was so important she didn’t physically die. Instead her body shot off into heaven when her life came to a natural end. Of course there is no evidence for this, even the bible says nothing about how Mary died. The belief that her body was lifted into heaven emerged about six centuries after Jesus’s time. But it became established tradition. It was handed down over centuries and the odd thing about tradition is that the longer it’s been going the more people seem to take it seriously. By 1950 the tradition was so strongly established that it became official truth: it became authority. The Vatican decreed that Roman Catholics must now believe in the doctrine of the assumption of the Virgin. Now if you had asked Pope Pius XII how he knew it was truth, he would have said you had to take his word for it because it had been revealed to him by God. He just thought private thoughts inside his own head, and convinced himself, no doubt on tortuous theological grounds, that it just had to be so.

None of this is particularly harmful when it is limited to the Virgin Mary, but what about the Pope’s personal convictions when it comes to, say, discouraging the use of condoms in Aids ridden Africa? Then the power of the church through tradition, authority and revelation comes with an appalling human cost. It would be unfair to pick on the Catholics. All religions are up to the same tricks; it could be Muslim Imams issuing fatwas. It’s the same principal. It’s issued by the authority. It then passes down through the ranks and all without a shred of evidence.