By contrast, why would anyone go to war for the sake of an absence of belief?

I do not, by nature, thrive on confrontation. I don't think the adversarial format is well designed to get at the truth, and I regularly refuse invitations to take part in formal debates. I was once invited to debate with the then Archbishop of York, in Edinburgh. I felt honoured by this, and accepted. After the debate, the religious physicist Russell Stannard reproduced in his book Doing Away with God? a letter that he wrote to the Observer:

Stannard went on to chide the Observer for failing to report a subsequent encounter between him and me, together with the Bishop of Birmingham and the distinguished cosmologist Sir Hermann Bondi, at the Royal Society, which had not been staged as an adversarial debate, and which had been a lot more constructive as a result. I can only agree with his implied condemnation of the adversarial debate format. In particular, for reasons explained in A Devil's Chaplain, I never take part in debates with creationists.*)

Despite my dislike of gladiatorial contests, I seem somehow to have acquired a reputation for pugnacity towards religion. Colleagues who agree that there is no God, who agree that we do not need religion to be moral, and agree that we can explain the roots of religion and of morality in non-religious terms, nevertheless come back at me in gentle puzzlement. Why are you so hostile? What is actually wrong with religion? Does it really do so much harm that we should actively fight against it? Why not live and let live, as one does with Taurus and Scorpio, crystal energy and ley lines? Isn't it all just harmless nonsense?

I might retort that such hostility as I or other atheists occasionally voice towards religion is limited to words. I am not going to bomb anybody, behead them, stone them, burn them at the stake, crucify them, or fly planes into their skyscrapers, just because of a theological disagreement. But my interlocutor usually doesn't leave it at that. He may go on to say something like this: 'Doesn't your hostility mark you out as a fundamentalist atheist, just as fundamentalist in your own way as the wingnuts of the Bible Belt in theirs?' I need to dispose of this accusation of fundamentalism, for it is distressingly common.

Fundamentalists know they are right because they have read the truth in a holy book and they know, in advance, that nothing will budge them from their belief. The truth of the holy book is an axiom, not the end product of a process of reasoning. The book is true, and if the evidence seems to contradict it, it is the evidence that must be thrown out, not the book. By contrast, what I, as a scientist, believe (for example, evolution) I believe not because of reading a holy book but because I have studied the evidence. It really is a very different matter. Books about evolution are believed not because they are holy. They are believed because they present overwhelming quantities of mutually buttressed evidence. In principle, any reader can go and check that evidence. When a science book is wrong, somebody eventually discovers the mistake and it is corrected in subsequent books. That conspicuously doesn't happen with holy books.

Philosophers, especially amateurs with a little philosophical learning, and even more especially those infected with 'cultural relativism', may raise a tiresome red herring at this point: a scientist's belief in evidence is itself a matter of fundamentalist faith. I have dealt with this elsewhere, and will only briefly repeat myself here. All of us believe in evidence in our own lives, whatever we may profess with our amateur philosophical hats on. If I am accused of murder, and prosecuting counsel sternly asks me whether it is true that I was in Chicago on the night of the crime, I cannot get away with a philosophical evasion: 'It depends what you mean by "true".' Nor with an anthropological, relativist plea: 'It is only in your Western scientific sense of "in" that I was in Chicago. The Bongolese have a completely different concept of "in", according to which you are only truly "in" a place if you are an anointed elder entitled to take snuff from the dried scrotum of a goat.'¹¹⁵

Maybe scientists are fundamentalist when it comes to defining in some abstract way what is meant by 'truth'. But so is everybody else. I am no more fundamentalist when I say evolution is true than when I say it is true that New Zealand is in the southern hemisphere. We believe in evolution because the evidence supports it, and we would abandon it overnight if new evidence arose to disprove it. No real fundamentalist would ever say anything like that.

It is all too easy to confuse fundamentalism with passion. I may well appear passionate when I defend evolution against a fundamentalist creationist, but this is not because of a rival fundamentalism of my own. It is because the evidence for evolution is overwhelmingly strong and I am passionately distressed that my opponent can't see it — or, more usually, refuses to look at it because it contradicts his holy book. My passion is increased when I think about how much the poor fundamentalists, and those whom they influence, are missing. The truths of evolution, along with many other scientific truths, are so engrossingly fascinating and beautiful; how truly tragic to die having missed out on all that! Of course that makes me passionate. How could it not? But my belief in evolution is not fundamentalism, and it is not faith, because I know what it would take to change my mind, and I would gladly do so if the necessary evidence were forthcoming.

It does happen. I have previously told the story of a respected elder statesman of the Zoology Department at Oxford when I was an undergraduate. For years he had passionately believed, and taught, that the Golgi Apparatus (a microscopic feature of the interior of cells) was not real: an artefact, an illusion. Every Monday afternoon it was the custom for the whole department to listen to a research talk by a visiting lecturer. One Monday, the visitor was an American cell biologist who presented completely convincing evidence that the Golgi Apparatus was real. At the end of the lecture, the old man strode to the front of the hall, shook the American by the hand and said — with passion — 'My dear fellow, I wish to thank you. I have been wrong these fifteen years.' We clapped our hands red. No fundamentalist would ever say that. In practice, not all scientists would. But all scientists pay lip service to it as an ideal — unlike, say, politicians who would probably condemn it as flip-flopping. The memory of the incident I have described still brings a lump to my throat.