We have met for afternoon tea on the edge of a vast frozen lake. Carl Djerassi, who has bright-white undulating hair, a neatly trimmed beard and an assertively charismatic manner, puts down his cane (he recently broke his hip, he explains) and removes from a leather case an old-fashioned steel contraption on which he rests his leg. We are in Madison, Wisconsin, where Djerassi completed his PhD long ago, and where a reading from his latest play has just been performed; yet as he looks out across the sunlit snow and tells me in a soft Viennese accent about his escape from Hitler and his Paul Klee collection - one of the most significant in private hands - I can't help feeling I am somewhere else altogether, somewhere in the Alps perhaps, in conversation with a colleague of Sigmund Freud.

Djerassi attended the same school as Freud, and has also had a lasting impact on the sexual politics of the past century, but Djerassi's life took off almost where Freud's ended. Djerassi was only 15 when Hitler invaded Vienna, only 16 when he wrote a personal letter to Eleanor Roosevelt requesting a place at an American University, only 28 (we are jumping a little here) when, in a small laboratory in Mexico City on 15 October 1951, he synthesised norethindrone, the first oral contraceptive, and changed women's lives forever.

'No one expected that women would accept oral contraceptives in the manner in which they did in the Sixties,' reflects Djerassi now. 'The explosion was much faster than anyone expected.'

Nor was it anticipated that some of the very women who might benefit from it would object to the Pill on political grounds. 'Germaine Greer was always a vociferous opponent of the Pill,' Djerassi says. 'We've had some unusually bitter exchanges. I've encountered this in a number of people, who think: they are poisoning us every day with hormones, why should we let them get away with this? If we had been Ms Djerassi, Ms Pincus, Ms Rock,' he says of himself and his male co-inventors, 'I bet you that much of the opposition would have been very different. But there were no women working in this field. If you did this research now, half of the people working on it would be women.'

The Pill is a large part of what paved the way for such advances, and Djerassi, widely dubbed 'the father of the Pill', is in many respects the author of our collective freedom. At the time, he was stunned by the political and social impact of his invention: so much so that what you might call the global side-effects of the Pill turned him from a straightforward chemist into a scientist-philosopher.

Now 83, Djerassi has spent most of his life exploring the consequences of the discovery he made at the age of 28. The first book he wrote for a general audience was called The Politics of Contraception; he has since explored the ramifications of scientific progress in five novels, seven plays, two memoirs and a book of essays. He refers to himself as a chemist, a playwright, and an 'agent provocateur'.

In truly provocative tradition, Djerassi is the first to object to his famous label. 'The whole idea of "the father of the Pill" - I hate that because there is no such thing,' he says sternly. 'I mean, if I am the father of the Pill, who is the mother?' If anything, Djerassi would prefer to cast himself as the mother of this invention. 'In order to give birth to anything, you need three people,' he explains, 'a father, a mother and a midwife.' He was the chemist who provided the initial substance, or 'egg'. The biologist Gregory Pincus, who co-ordinated its experimentation as a contraceptive, might be seen as the father. And the physician John Rock, who oversaw the first clinical trials (conducted in Puerto Rico because it was a felony to administer contraception in Rock's state of Massachusetts), was the midwife. Both Rock and Pincus, who were much older than Djerassi, are now dead.

Contraception was not the original reason Djerassi and his team in Mexico were researching the drug. Though Pincus, in the United States, was operating with the support of the eugenicist and birth-control activist Margaret Sanger, Djerassi was a Jewish refugee fleeing Hitler - population control couldn't have been further from his agenda. He was working towards an orally active form of progesterone as a remedy for severe menstrual disorders, certain conditions of infertility, and cervical cancer.

What's more, his experiments were conducted in a climate whose subtleties may well have informed his political sensitivity later on: the Americas were studded with survivors from both sides of Hitler's regime; many of them were scientists, and some of his eminent elders and colleagues were almost certainly Nazis and anti-semites. In This Man's Pill, a memoir published on the 50th anniversary of the Pill, Djerassi asks whether this reduced their scientific contribution, and boldly considers the answer to be no. (On the occasion of his 80th birthday, the Austrian government put Djerassi's face on a stamp. It was accompanied by the poignant caption: 'Born 1923, Expelled 1938, Reconciled 2003'.)

'I am not a Pill-pusher,' Djerassi tells me emphatically, as we take our tea. The drug has made him rich, but not in the way that people might think. He doesn't get royalties every time one of the 100 million women on the Pill pop one. He bought shares in Syntex, the small Mexican company where he did his research. 'They were shares I had bought on the open market - other people could have bought them but no one believed in the future of the company, which developed very much because of work that I and other colleagues conducted. We deserved it.'

With the proceeds, he bought the 1,200 acres where he now lives, in the Santa Cruz mountains not far from San Francisco, and began an exceptional art collection; over the years he has kept his 150 most precious Klees, which have been bequeathed to the San Francisco Museum of Modern Art, and sold his Picassos, Giacomettis and Henry Moores in order to fund an artists' colony for the Picassos and Moores of the future. He called his huge territory SMIP, an acronym for Syntex Made It Possible, but visiting artists have played around with other possibilities: 'Sexy Man Invents Pill'; 'See Me In Private'; 'Sado-Masochism Is Prohibited'.

Djerassi noted many years ago that one of the earliest writers to use the word 'Pill' with a capital 'P' was Aldous Huxley, and he was not blind to the implication that the steroid he had synthesised might become a problem as well as a solution in the brave new worlds of the future. The fact that he is the only survivor among the Pill's so-called parents is no bad thing, he suggests, because he is the only one of the three who was realistic about it. 'Pincus's position was: "This is the cat's meow, this is the answer, there are no side-effects." That is bullshit. Nothing has no side-effects. Two weeks ago, a woman died from drinking too much water - well, who would ever think that water was a poison?'

We run through some of the Pill's reputed side-effects: increased risk of thrombosis ('unequivocal'); increased risk of breast cancer ('a trickier one'); reduced risk of ovarian cancer ('established', a reduction of 50 per cent). But the side-effects Djerassi is most interested in are not the physical ones. Many years ago, he coined the terms 'contraceptive hardware and software'.

'Contraceptive hardware is the method we use for birth control, whether it's the Pill or abortion or abstinence or whatever it is,' he explains. 'The software is the cultural, economic, legal, political, public health issues - women's rights more than any other, perhaps. Those are much more difficult issues than scientific ones. When people talk about, "Why not a male Pill?" Scientifically we solved that a number of years ago. But we haven't solved the software problems: the most important one is, would you as a woman put your entire reproductive risk in the trust that he has remembered his Pill?'

Just think about the power relations involved, he argues: a male Pill, which theoretically would allow men to share the burden of contraception, would, in fact, take away women's control over their own fertility - and potentially, everything the original Pill gave us along with it. In other words, a male Pill would set us back at least 50 years.

'One of the penalties of the Pill is its effectiveness,' Djerassi proposes. 'In many cases the man takes it completely for granted - now men who would have been willing to use condoms do not: it is yet another thing that is put on women's shoulders. Another penalty,' he goes on, 'is that because that Pill has enabled women to make these decisions, and that coincided with a much wider entry of women into professions that were not open to them, they postpone child-bearing.'

His latest area of interest is the separation of sex from reproduction: if the Pill enabled us to have sex with out having children, then we are now living through its natural bookend: the possibility of children without sex. Djerassi suggests that in the future we will freeze our sperm and eggs, get sterilised and check out our sperm and eggs from the bank when we want them later. 'Then you might as well forget about contraception. I am absolutely convinced that is the direction in which we're going in the long run in the Western world.' Then he adds, on a more personal note: 'I'm a very good example - I didn't want to use condoms for the rest of my life and I got sterilised at a very reproductive time. I was, in my mind, finished with having children. But there's a risk involved - suppose your children die, suppose you want to have children again?

In July 1978, Djerassi's only daughter, Pamela, committed suicide. She had left a note for her husband, and disappeared in the vast woods on the SMIP property. When she was found four days later, it was Djerassi who saw her body first.

'In the last three years of her life she was without doubt my closest confidante, and I was probably hers,' says Djerassi, who is given to unflinching self-examination. He gazes across the frozen lake, and recalls: 'We went cross-country skiing, she and I, for a few days... I'm looking out at this because it was sort of like this. It was in this clean and calming but severe environment. It isn't often that you're together with someone for 40 or 50 hours in total solitude. I told her things I've never told anyone else - things about my relationships with women. I was going through a divorce. It's ironic: She was the only woman in my life to whom I felt I could say those things - I was asking for counsel, and she took it that way. It was an extraordinary experience.'

Yet nothing in the behaviour immediately preceding Pamela's death gave her father a clue to her intentions. She was an artist; her work was not going well. 'She really was suffering absolutely from clinical depression,' Djerassi says, 'and it was up and down.'

Pamela was born in 1950. A few weeks before her birth, Djerassi was still married to his first wife, Virginia, whom he'd wed when he was 19. They had moved to Mexico together when he went to work for Syntex, and six years later Djerassi announced that the woman with whom he was having an affair (a year before his synthesis of the Pill) was pregnant with his first child. Vir ginia granted him a very quick and courteous divorce, and he married Norma, just in time for Pamela's birth. He and Norma had another child, Dale (who later married Robert Maxwell's daughter and had a son), and it was Norma from whom Djerassi was getting divorced in the late Seventies. In 1977, he met Diane Middlebrook, his current wife, a distinguished professor, feminist, poet and biographer.

Three years before she died, Pamela did something radical that might seem to go against the grain of her father's great discovery: at the age of 25, she decided to be sterilised. Her husband, whom she had met at university, was a doctor, and while no doctor would normally per form that operation on such a young woman, she persuaded a colleague of his to do it. 'She talked to me per haps more than anyone else about it,' Djerassi tells me. 'She made a very persuasive case. This was at the height of concern about the population explosion; there were so many poor, unwanted children, she said, why bring another one into this horrible world? "If I want to have children, I can adopt them." Well, I would not have advised her to sterilise herself, because it's pretty irrevocable, but I could understand that.

'The idea of suicide has of course never left me,' Djerassi reflects. He has returned to it many times in his fiction. 'I believe suicide should not be kept quiet - one shouldn't be ashamed of talking or writing about it, it does a dishonour to the person who killed herself. Suicide is a message to the survivors - it's very different from any other form of death - and one should have at least the respect to read it.'

One of Djerassi's responses to Pamela's message was to fund women artists, to give others like her what she could not have. He put her house and the bulk of her estate (she had come into a trust fund built with Syntex shares) into a scholarship, which then turned into a full-scale artists' colony that now accepts men as well as women. He often wonders what she would have thought 'about 500 artists going to a place that would not have been there had it not been for her death'.

Another question Djerassi has asked himself many times is: What if the Pill had never existed? Of course, from a personal point of view, it changed him enormously - the way he thought, the way he worked, the way he lived, and it changed the lives of those around him. Syntex Made It Possible. But his claims on the world stage turn out to be surprisingly modest.

When I ask whether he thinks the Pill kick-started the sexual revolution, as is usually claimed, or whether it was merely a hitchhiker on the already paved road to liberation, he replies: 'What we forget is what happened in the Sixties: hippy culture, drug culture, Timothy Leary, rock'n'roll - and then you had the Germaine Greers, and I mean this in a positive context. The one common denominator was sexual liberation, or promiscuity.' He stops to allow himself a little chuckle. 'Anyone who thinks that was all caused by the Pill must be smoking something.'

Djerassi pauses to imagine a world without his historic invention and says, in calm conclusion: 'That the Pill facilitated that direction is absolutely true, but I believe it would have happened anyway. Not as explosively, but more gradually. It would have happened in exactly the same way.'