I do not like to give offence to Christians. I say, if asked, that I’m agnostic. But the truth is I'm an atheist, impatient with the simple-mindedness of orthodox religion, its lack of imagination, its bafflegab. I never go to church. I’ve never prayed. I’ve not been Christened, yet. So, when I began my novel Quarantine (which retells the story of Christ's forty days of temptation in the wilderness) I expected – indeed, intended – to inflict some bruises on religious dogma. An easy target, I thought. Christendom has never been in such an undernourished and diminished state. Every week the godless mechanics of the universe, from Big Bang to the tiny chemical percussions of the brain, are revealed in finer detail. Meanwhile, with two thousand years in which to collect its evidence, the church – no longer able to claim that Earth and all its creatures have come ready-made from God’s Creation Workshop, or that thunder is really the Almighty stamping with displeasure at our sins – has been reduced to ritual and display. Plenty of incense smoke, but no divine cigar.

It would be a simple matter. Take a venerated Bible story (Christ’s Judean fast), add a pinch of hard-nosed fact (nobody gong without food and drink could survive for anything like forty days) and watch the scripture take a beating. Quarantine with Science as its sword would kill Christ after only thirty days in the wilderness. There’d be no Ministry or Crucifixion. The novel would erase two thousand years of Christianity. This would be my party-pooper for the Millennium.

Indeed, Quarantine did slay Christ. But novels have a way of breaking loose from their creators. That’s why they’re fun to write. Science does not triumph unambiguously in the book. Faith is not destroyed by Doubt. Jesus does not let me kill him off entirely. Rather than having to endure the wrath of Christians, as I expected, I found that Quarantine had been received by many British readers as a spiritual and scriptural text, an enrichment rather than a challenge to their faith. What’s going on? Correspondents, who have been bombarding me for months with their religious tracts, claim that Quarantine could not have been written by an atheist. ‘The Grace of God,’ they say, ‘was standing at your shoulder as you wrote.’ They’re wrong, of course. They do not understand that books have agendas of their own, no matter what the author may believe. Novels and their writers are not mere mirror images. It’s the imp of story-telling at our shoulders, not the Grace of God.

So, I’m just as godless as I ever was. But nobody could spend two years writing such a book and remain undisturbed by it. Quarantine has brought me out of hiding. I no longer use the term agnostic as a shield. I present my atheism as something richer than just the bleak and heartless absence of belief. For me it is a powerful persuasion in its own right. A universe which is an outside job, inflicted on us by a Creator in seven days, is a lesser marvel than a universe which is an inside job, the slow, painstaking product of natural forces. Evolution is a greater wonder than all the gods. The Blind Watchmaker is more inspiring than Blind Faith.

Here, I think, is the challenge for all of us who have not been issued with the gene of religion. In squaring up to the blessed and perplexing mysteries of life we must show how human consciousness can be ecstatic and deeply spiritual without the vulgar, sentimental comforts of a god. Atheists, if they will seek transcendence in science and the natural world, could prove to be the new mystics for the new millennium.