I don't expect Christians to see God as a metaphor, but that's what he is. Perhaps it might be clearer to call him a character in fiction, and a very interesting one too: one of the greatest and most complex villains of all - savage, petty, boastful and jealous, and yet capable of moments of tenderness and extremes of arbitrary affection - for David, for example. But he's not real, any more than Hamlet or Mr Pickwick are real. They are real in the context of their stories, but you won't find them in the phone book.

The book is second only to the wheel as the best piece of technology human beings have ever invented. A book symbolises the whole intellectual history of mankind; it's the greatest weapon ever devised in the war against stupidity.

The state of mind which I put myself when I tell a story is one in which superstition flourishes very easily. And I welcome that because it helps me.

The intentions of a tool are what it does. A hammer intends to strike, a vise intends to hold fast, a lever intends to lift. They are what it is made for. But sometimes a tool may have other uses that you don't know. Sometimes in doing what you intend, you also do what the knife intends, without knowing.

D'you know how embarrassing it is to mention good and evil in a scientific laboratory? Have you any idea? One of the reasons I became a scientist was not to have to think about that kind of thing.

I write almost always in the third person, and I don't think the narrator is male or female anyway. They're both, and young and old, and wise and silly, and sceptical and credulous, and innocent and experienced, all at once. Narrators are not even human - they're sprites.

We feel cold, but we don't mind it, because we will not come to harm. And if we wrapped up against the cold, we wouldn't feel other things, like the bright tingle of the stars, or the music of the aurora, or best of all the silky feeling of moonlight on our skin. It's worth being cold for that.