Hans Holbein appeared to me in a dream, instantly recognisable because of the unflattering hat, like a flat shower cap, that he wears in his self-portrait. He gave me good advice about my next novel, but when I went to write it down, shadowy people stole my paper. I tore around the dream-world wrestling for notebooks, but they were whipped away as soon as I laid a pen on them. I got cunning and made a play for some baking parchment, but finally, after a tussle with a ghostly hand over a paper doily, I gave in and woke up.

No need to ask whether my subconscious is struggling with the notion of being told what I should and shouldn’t be writing. This year’s Booker shortlist was one to which few could take exception, but you have to have a story – a controversy, however fatuous – so we have seen the resurrection of the time-worn debate about the value of historical fiction. Authors get tired of saying, “It’s all historical by the time it gets to the printers”. Sizzling topicality soon turns limp and tepid, and nothing dates quite so fast as a novel about the future; the grim forecasts of dystopian fiction are almost always exceeded in nastiness by developing realities. In any case, it is no part of a novelist’s duty to act as a first-strike force. Her skill lies in imaginative interpretation, not knee-jerk reaction. We have people well capable of processing the present; they’re called journalists, and they need to be kept in work.

The boundaries of the term “historical fiction” are now so wide that it’s almost meaningless, so use of the term is beginning to look like an accusation, a stick to beat writers with: you’re historical, you weaselly good-for-nothing, you luxury, you parasite. The accusation is that authors are ducking the tough issues in favour of writing about frocks. There is a certain strand of historical fiction of which this is certainly true; it is chick-lit with wimples. But that is not the kind of historical fiction that is under attack. It is too soft a target. The grumbling is aimed at literary fiction set in the past, which is accused of being, by its nature, escapist. It’s as if the past is some feathered sanctuary, a nest muffled from contention and the noise of debate, its events suffused by a pink, romantic glow. But this is not how, in practice, modern novelists see their subject matter. If anything, the opposite is true. A relation of past events brings you up against events and mentalities that, should you choose to describe them, would bring you to the borders of what your readers could bear. The danger you have to negotiate is not the dimpled coyness of the past – it is its obscenity.

What underlies the objection, I think, is not just misunderstanding of history itself, but contempt for its uses. It is true that in the days when statesmen and generals learned history (probably tables of kings and queens by rote) they were not conspicuously good at avoiding the errors of their predecessors; each turn of events seemed to strike them with the force of novelty and, startled, they would proceed to cock it up all over again. Henry Ford’s contention that “history is more or less bunk” is perhaps not as crass a statement as it is often taken to be, because a good deal of what we think we know about the past is unverified tradition and unexamined prejudice. Tables of kings and queens, though not very useful, are at least verifiable, but no one learns that kind of history any more, and much of what we retain about the past is a collection of factoids, received opinions and accumulated moral judgments. This argues for better history, rather than less history. To try to engage with the present without engaging with the past is to live like a dog or cat rather than a human being; it is to bob along on the waters of egotism, solipsism and ignorance.

History offers us vicarious experience. It allows the youngest student to possess the ground equally with his elders; without a knowledge of history to give him a context for present events, he is at the mercy of every social misdiagnosis handed to him. The old always think the world is getting worse; it is for the young, equipped with historical facts, to point out that, compared with 1509, or even 1939, life in 2009 is sweet as honey. Immersion in history doesn’t make you backward-looking; it makes you want to run like hell towards the future.

It’s always surprising that, when faced with that staple question of personality-based quizzes, “Which century would you like to have lived in?”, people will fancy themselves as 18th-century dandies or ladies from the pictures of Gainsborough. The 18th century’s elegant, but only till your appendix bursts or you catch an STD. People who covet the past need to consider their medical needs and specify their social class. “Aristocrat” is usually a good bet, though not in France in 1793.

The past is not dead ground, and to traverse it is not a sterile exercise. History is always changing behind us, and the past changes a little every time we retell it. The most scrupulous historian is an unreliable narrator; he brings to the enterprise the biases of his training and the vagaries of his personal temperament, and he is often obliged, in order to make his name, to murder his forefathers by coming up with a different take on events from the one that held sway when he himself learned the discipline; he must make the old new, because his department’s academic standing depends on it.

Once this is understood, the trade of the historical novelist doesn’t seem so reprehensible or dubious; the only requirement is for conjecture to be plausible and grounded in the best facts one can get. In any event, it is wrong for critics to be prescriptive about what the novelists of any generation should write. Most of their prescriptions are issued in deep ignorance of how a novel gets on to the page. A novelist doesn’t sit at the keyboard sucking her thumb, thinking “what next?” A novel arrives whether you want it or not. After months or years of silent travel by night, it squats like an illegal immigrant at Calais, glowering and plotting, thinking of a thousand ways to gain a foothold. It’s useless to try to keep it out. It’s smarter than you are. It’s upon you before you’ve seen its face, and has set up in business and bought a house.

What really disconcerts commentators, I suspect, is that, when they read historical fiction, they feel their own lack of education may be exposed; they panic, because they don’t know which bits are true. So here is a handy pocket guide. Every time the author writes, “He thought that . . .” or “She felt that . . .”, she’s making it up. We never know what people thought or felt, unless they kept frank and full journals. And the world is full of people who lie to their own diaries.