The following letter is excerpted from the new Twelth Planet Press collection Letters to Tiptree, edited by Alisa Krasnostein and Alexandra Pierce, published to mark the hundredth anniversary of Alice Sheldon's birth.

Dear Dr Sheldon,

I wondered, when I planned writing this letter, how should I address you? Maybe I'm just British, but it worried me. I can't call you "Alice"; or "Tip". That would be rude; I never even met you. "Dear Tiptree" seemed like a possibility, but though "Tip" may have been your handle, among friends, "Tiptree" was never your name. "Mr Tiptree" sounds ridiculous, "Mrs Bradley Sheldon" anachronistic. You were Major Bradley in the US Army; I suppose you were Agent Sheldon in the infant CIA? You had so many titles; so many brilliant careers you seem to have sampled and tossed aside. . . . Then I remembered you had a PhD in Psychology, and I felt my path was clear.

Anyway, the first thing I need to say is what every writer wants to hear: I love your writing. I loved your writing before I had any idea you were a secret agent. I should explain that I've read science fiction all my life, but I've never been a fan in the technical sense. I had no idea the Science Fiction Community existed until my first novel was "hailed" as SF, back in the eighties. I knew nothing about the controversy around dazzling, honours-laden, "ineluctably masculine" "James Tiptree, Jr." until it was long over, and you had been unmasked. I have to confess something: I was disappointed. In the seventies I had found plenty of sexual-revolutionary US female SF writers to admire (Ursula Le Guin, Suzy McKee Charnas, Joanna Russ, Vonda McIntyre . . . for the genre, it was a crowd!). There were men who were okay, doing their best according to their lights (Chip Delany, Fred Pohl). But James Tiptree was different. I remember reading your first novel (Up the Walls of the World) when it was new, in its yellow and red Gollancz jacket, and thinking: at least there's one. Tiptree gets it, he sees what the problems are. . . . And you were gone. It was a shame.

If I was completely fooled, I was in good company. When someone reads the transcript of Khatru 3 (a free-ranging discussion of sex and gender issues, organised by fanzine editor Jeffrey D. Smith, in 1975) it's clear that Ursula Le Guin, Joanna Russ et al. never doubted that Tip was a male fellow traveller—although they took issue with his effusive, dear lady manner, and his tendency to put Woman on a sentimental pedestal. You were having fun, I suppose. But I sometimes wonder, were they disappointed too? Did they wish "Tip" could have been the man they thought he was? The proof that science fiction could change? That male science fiction writers could be everything the SF world wanted, and win all the prizes, and still didn't have to be sexist?

How did you ever get away with it? The short answer is that you didn't; not for long. You were Tiptree for nine years: heaped with praise; the man of the moment. But your failure to appear in public had quickly attracted attention, and there were doubts about your sex, based on your preferred themes. Your fans, bless them, felt they had a right to know who you really were, and were soon trying hard to find out. Meanwhile, you were playing with fire. You must have known that discovery would cost you your place at the top table, yet you formed intimate, confessional friendships by mail. You shared personal data in correspondence. You didn't say no when you were invited, and expected, to play a prominent part in the big science fiction/sexual politics debate—an issue that was so important in your work, and so vitally interesting to the real Dr Sheldon. Something had to give.

The other answer is that you were a natural for the role. You were a skilled writer with a science doctorate. You knew science fiction: you'd tried writing it already, but without the help of "Tiptree" garnered only a handful of rejections. You'd been testing the limits of what a woman could do and be in a man's world (a succession of male worlds) your entire life, if we count the childhood adventures with your redoubtable mother in Africa. Journalist, Intelligence Officer, Experimental Psychologist, Spy . . . you were protected, I'm sure, by the sense of entitlement that children of privilege never lose, but you'd had to learn to hide in plain sight, like the escapologist mother and daughter in "The Women Men Don't See." I suspect you'd learned to enjoy the danger, too. And the timing was perfect. Science fiction, primed by the New Wave, infiltrated by the ferment of sixties and seventies radical movements, was open as never before to the challenges you had to offer.

You wrote other stories (cover stories, maybe?), that were polished, competent, and unthreatening—like your family-values Scientific Apocalypse tale "The Man Who Walked Home"—but ironically it was probably the hard-hitting feminist material that sealed the success of your masquerade. You wrote about brutal rape and brutish lust, with considerable style and in shockingly candid language. Sometimes blackly comic, sometimes deadly serious, you portrayed man, the male of the species, as a tortured soul, helpless in the grip of his urges. Man, the slave of Life's meaningless, never-ending expansion-drive; the monster who can't be tamed. . . . And while your female colleagues saw other nuances, male writers and critics simply loved you for it. They felt recognised: vindicated by a fearless older brother.

The shock value of your sexual imagery has faded. Today, the famous lust scene in "And I Awoke on the Cold Hill's Side" (one of my favourites) reads like a sideshow in a powerful story that uses sexual excitement as a metaphor, in a savage critique of US imperialism. But your preoccupation with sex-as-death can't be deconstructed so easily, and your profound pessimism about the human race is as haunting as ever. You said once in an interview that "the birth and growth of Nazism" was your "central generation event." I believe you, but I think it went deeper and wider than that. Nagasaki and Hiroshima, and the madness of Mutually Assured Destruction, were probably also entries in the catalogue of horrors that made you see your own humanity as the stuff of nightmares. Maybe your lab work didn't help, either. Experimental Psychology can be a nasty business, and a dissertation on "Responses of animals to novel stimuli in differing environments" sounds a bit sinister to me. Not much fun for the white mice, I'll bet.

You were a child star, Alice in Jungleland with your picture in the papers, before you were nine years old. You first tried suicide when you were a teen. Many child stars find celebrity a hard act to follow; many celebrated artists have struggled with depression, as you did all your life. But you were not a quitter. You kept going, having a wild time, a tumultuous life full of triumphs and disasters, and for your swansong you blazed a remarkable trail, in the quintessentially US American literary genre of science fiction.

The last thing I want to do is be one of those people who lay claim to the dead: I'm not going to speculate on your "real" sexuality. But I do feel personally proud of you, and enduringly grateful for what you achieved when you decided, for such pragmatic and insouciant reasons, to game your science fiction career. You didn't prove that science fiction can change. But you did make any bloke who says women can't do it look like an idiot. Permanently. And that still makes me grin.

I wonder what you make of the fact that we've survived, despite all our awful faults, into another century? You'd probably tell me nothing's changed. We're still well on course for annihilation, doomed by our biology to destroy ourselves and take the living world with us. And I'd have to agree, you could have a point. But if you were still writing that "Last Flight of Dr Ain" kind of story, and if I could talk to you, I'd tell you my own motto is never say die, and la lutte continue. There's more to life than a giant penis, piercing the heavens in search of its doomy, Wagnerian love-death. The future's not out there, it's right here on Earth, all around us, and full of surprises.

Well, that's all for now. Thanks again for the stories. Thanks for your wildness, and your wicked sense of humour.

All best, Gwyneth Jones