It is impossible to begin at the beginning. Any scientist can tell you what happened in the first three seconds after the Big Bang, but none can say for sure what happened in the three seconds previous.
So it is with fiction; the moment I have begun, I can tell you something about the beginning. I might even be able to say: "Like most people I lived for a long time with my mother and father ... " But when I talk about what happened before the beginning, I hazard myself, I use colour and sound, I find another story - but it will be a story and not a fact. The fact is that before something happens there is no knowing what is happening. I use the present tense there with good reason; "is happening" is a place of intense activity, but below ground. Creative work of any kind and in any medium relies on this "is happening" but cannot will it, summon it, or even often know that it is there.
So when I look at the email that asks me to write something about how I came to write Oranges Are Not the Only Fruit, I can do one of two things; invent a plausible back-story, or try to tell some truth about the process of making.
One of the things I have noticed over the past 20 years is that the later books explain something about the earlier books: in The PowerBook (2000), I wrote: "I can change the story. I am the story." This was because I had been thinking about how much better it might be to read ourselves as fictional narratives, instead of as a bloated CV of chronological events. Once we surrender ourselves to the tyranny of facts, it is difficult to re-find free will.
The tyranny of my facts - the pre-Oranges facts - were that I was adopted by working-class Pentecostal parents who wanted me to be a missionary. I was stuck in class, stuck in religion, stuck in a dead-end northern town. I was female, both of my parents had left school at 14, and my father could barely read. Line all that up and it doesn't look like the route to where I am and who I am now.
For me, possibility was not in the facts, but in what I could imagine. What we can imagine always begins as a story.
So far so good ... But this year I found my adoption papers.
I was clearing my father's flat, after his second wife had died, and in the middle of the gas bills and ancient bills of sale, were those 1960s forms, typed on a ribbon typewriter, signed in fountain pen, a message in a bottle from another world.
So far so good ... But that other world was me.
And I realise now that much of what I was trying to do in 1984, when I was writing Oranges, was to control the out-of-control circumstances of my own beginnings. If I could tell it again, it would belong to me in a way that I hadn't really belonged to anybody. I looked at Weight (2005), my retelling of the Atlas myth for the Canongate Myths series, and I read myself saying: "I want to tell the story again ..."
Yes, always. Telling the story again is how stories were passed on when we lived in an oral tradition, working from generation to generation. The Jews, without homeland, without territory, passed themselves on exclusively through the telling of stories - the genealogy of Genesis up to the present day. The Jews, without homeland, learned to live on the cusp of history and memory, the place where public and private realities merge, allowing that strange thing called identity to happen.
Who am I? An obvious question for an orphan. But in the diaspora that has become a fact of life for so many of us all over the world, living elsewhere, intermarrying, cut off from our roots, miles from our families, oil-rig working in what feels like outer space, the "who am I?" cannot be answered easily, or conventionally.
I believe in stories, in story-telling, because a story can answer a question without reducing that question to banality. "Who am I?" is a huge question, and the answer develops, unfolds, reveals itself throughout the whole of our life. At birth, we are only the visible corner of a folded map. The geography of the self is best explored with a guide, and for me art is such a guide. I write fiction because I want to get nearer to the truth.
So is Oranges a self-willed autobiography of a kind? I don't think so. I think it is an explanation, in code, of myself to myself, but all my books are that, and if they were only that, no one else would want to read them.
The trick is, the gift is, the miracle is, that what begins as private notation becomes language other people can use. The books we love speak for us and speak to us. I am always in dialogue with the books that have affected me. Stories start other stories. That's how it is.
· Next week: John Mullan looks at readers' responses to the novel
