Cynthia Ozick, whose novel, Foreign Bodies, has been shortlisted for the Orange Prize, is not keen on her age being mentioned, although when she looks at the number, "it seems dreadfully old". But she thinks it unremarkable. Ozick thinks writers are judged on their work, not their age. Quite right. What has age got to do with the quality of her writing?

Perhaps I'm biased, being an old woman, but I get the impression that the world is often surprised to find that we can do much at all, other than dodder around being forgetful, or do the odd bit of gardening, knitting, heating up soup or crawling round the block with a small dog. Write a prize-winning book! Heavens, what next? Have a brain? Have thoughts of any depth? Accumulate experience and wisdom? Be witty, amusing or worth engaging in conversation? Surely not.

Octogenarian novelists "on the whole [are] no bloody good," said Martin Amis. "You can see [them] disintegrating before your eyes as they move past 70." Did he mean Ursula le Guin, Fay Weldon and Ruth Rendell? After 80, you're meant to atrophy. Physically and mentally. Especially if you're a woman. I don't see many jaws dropping when an old man carries on writing: William Trevor, Saul Bellow, Thomas Hardy.

I am also bitterly disappointed to find that Simone de Beauvoir seemed to agree with Amis. "A novel is the least suitable form of literature for the elderly writer," she said drearily, because they risk "simply repeating things" and are "past imagining new possibilities". Wrong, Simone, wrong. If we all thought like that we might as well throw in the towel at 79. I prefer the philosophy of Ozick – forget the numbers, think about the quality. And I hope she wins.