It was the 60s and acid was king. It was hip to be mad and cool to be crazy, and twice a week, for four years, David Gale spent an hour with an eminent psychiatrist, trying to get his head around his own personal terrors. Only the shrink was on a trip of his own...

I had a 10 o'clock appointment with my psychotherapist at Primrose Hill. When I got there, he was naked in the kitchen. He was dandling a naked baby and telling me that he had been up all night fucking a South American woman. The baby belonged to Roy, one of Cooper's patients. Roy and Cooper would go out in Roy's VW camper van and pick up chicks and fuck them. Roy's wife had a leg brace from poliomyelitis. But the South American woman was not a pick-up, she was the girlfriend of another patient of Cooper's. This guy had jumped under a tube train two days ago. His father had been a butcher. Cooper said the guy had grown up watching meat being chopped and fantasised that his father was chopping him up. Apparently the train had cut him very neatly in two. Cooper said that in the moment of his death, the guy had achieved something he had been craving all his life: to be treated with respect by his father.

I wasn't sure whether my session had begun. For a start, we weren't in the right room, but then formalities of this sort had been observed only sporadically in the past few months. I thought what I ought to think was that all this wildness was good for me. I was reluctant to admit that, in fact, I simply felt uncomfortable.

That was 1970. Throughout the year, the eminent psychiatrist David Cooper had also been engaged on an entirely coherent project, one that would challenge the very basis of civilisation. The publication of his book The Death Of The Family in 1971 would confirm that, despite the author's apparent waywardness, a powerful and visionary mind had been at work, on a profoundly unsettling text. The book, published by Penguin, was both lucid and elliptical, containing a coruscating attack on a hallowed institution.

As the book's title suggests, Cooper felt that the family was over. He described it as "that system which obscurely filters out most of our experience and then deprives our acts of any genuine spontaneity". It was a merciless space in which its victims were petrified, dehumanised and systematically stripped of their critical faculties. Far from maintaining the sanity of its members, the family drove them mad. "The family," asserted Cooper, "since it cannot bear doubt about itself and its capacity to engender 'mental health' and 'correct attitudes', destroys doubt as a possibility in each of its members." What the family teaches, Cooper declared, is that "one is not enough to exist in the world on one's own". This leads to a passivity that submits to invasion. The invaders are, of course, members of the family. If one reacts to this too noticeably, perhaps by becoming paranoid, one of the family's most insidious protectors will intercede to defend the family against the autonomy of its members. Its name is psychiatry.

Cooper and his colleague, Ronald Laing, were the champions of anti-psychiatry. In the widely read books that they produced in the 60s and 70s, they not only laid waste to complacent notions about the nature of madness and badness but articulated an impulse that lay beneath the dope and love beads of the era's stereotype. The anti-psychiatrists saw that some of the participants in the decade of love and revolution were caught up in a determined attempt to deconstitute reality. At a personal level, this entailed finding out just how mad you could sanely be. The anti-psychiatrists offered a context and an itinerary.

On the last page of The Death Of The Family is a passage I find rather engaging. "There was once a young man who until the age of nine had longed for his father to chastise him. One day, at long last, his father actually raised his hand with the intention of hitting his son's backside. As he did this, the father landed a backsider on the face of his voyeuristic wife." Cooper gets the details wrong - I was 11, not nine, and it wasn't my backside my dad was aiming at, it was my head. We were sitting at the breakfast table. As he drew his hand back, my father inadvertently slapped my mother in the teeth and she cried, "Ernest! Don't you dare hit him so hard!" He lowered his hand. I think my version - the authentic version - is better.

My father was a biochemist at Cambridge. On Sunday evenings when I was a little boy, he would take me to his laboratory to watch him "sow the bugs", that is, smear bacteria on to a nutrient gel so that they would grow overnight into colonies large enough to experiment with on Monday mornings. My father was, and continues to be, a gentle man. He never hit me, despite snapping just that once back in the 50s. By the time I reached my teens, however, I had decided that his world of precise measurement and endlessly repeated experiments was the pits. It would be another 20 years before I realised he had dedicated his career to a quest for the Secret Of Life. As a teenager, however, I convinced myself that I must cut my ties with this suffocating life and head off in the direction suggested by Elvis and later confirmed by Jack Kerouac.

The 60s began in 1962, when I was 18. By 1963, I was having trouble with the new freedoms. Suddenly you could do anything you wanted. I took this as a fiat: you should want to do Anything. At times this felt quite onerous. My friends and I had recently become members of the Beat Generation. Sure, we were white, middle-class boys living at home with our parents, but there was every possibility we might become White Negroes. These were figures conjured by Norman Mailer, whom we had seen talking on black-and-white television. White Negroes, Mailer had said, were a new phenomenon, American existentialists who had divorced themselves from society "to set out on that uncharted journey into the rebellious imperatives of the self". The white bohemians had found jazz in certain quarters of certain cities and there they had come face to face with "the Negro". In this bebop moment, "the hipster became a fact in American life". Far out.

Crucial to the maturation of the emerging beatnik was the regular inhalation of pot. I should say that, in those days, the word "pot" was very cool, like "digital". That it now sounds like something your uncle would say is because we are uncles now. In addition to unlocking the synaesthesia of the inner cinema, the cannabinoids bestowed the gift of Transparency. This was really quite something. With Transparency, you could think about your life, or the society in which you lived, or the values you had absorbed, and you could see right through them. Some years later, it would become appropriate to say this was a form of deconstruction, but that hadn't been invented yet. There was a difference, however: you didn't have to be clever to deconstruct in this manner, you just had to be stoned. Truths were made apparent, they were not worked out.

So I saw through it all. Saw it for the charade it was. Saw its falseness. Unfortunately, I also saw through myself. My falseness. In the summer of 1963, I holidayed with some fellow beatniks in Ibiza, where bulk purchase of pot was a routine affair. This was when the inner and the outer first became confused. Every night we would roll big spliffs without tobacco and laugh for hours with fuzzy, bloodshot eyes. My girlfriend, Maureen, was with me. I realised I could hear a sort of dull whine. I glanced across the room at where my mother was sitting. But my mother wasn't on holiday with us. You wouldn't bring your mother. As I gazed at her, the flesh of her face flowed and reformed. It was Maureen. Crikey. To say the least. I'd read a Penguin on Freud, so I had a notion of what might be going on. That night in bed with Maureen, we had dynamite stoned sex and afterwards I lay for hours, enveloped in a streaming, twittering miasma of bright, fragmented faces, figures and cartoon creatures. Something had shifted.

Back home, I carried on smoking. I noticed that my experience was becoming less social, more self-absorbed. My fellow angel-headed hipsters would be bellowing delightedly or bowing their heads to some sounds, but I would fall silent and uneasy. When I glanced at them and caught their eye, I would look away, lest they saw through my eyes into my mind, where 20 years of composure were starting to unravel.

So unsettling did these paranoid episodes become that I decided to stop smoking pot. It might all have ended there, had it not been for the arrival of acid.

In those days, doses were big. None of your namby-pamby little tabs for the 60s pioneers, thank you. It was 500 mikes and say goodbye to your backside. Within 20 minutes I was orbiting the sun, suffused with an elation that permeated every electric molecule of my being. I saw the centre, I extended to the outermost reaches of space, I was the hum of the dynamo. And this lasts for eight hours, I thought. Too much.

With that thought, the thing turned over. I fell from Eden into the most hellish place I've been to in 57 years. The room disappeared. I saw my father's disembodied head, it flowed into the face of a bulldog, blood oozed from its eyes, nose and mouth, it shuddered and became a vagina, my mother's head emerged from it. I buried my face in the pillow. But this wasn't a close-your-eyes thing. You couldn't get away. Eyes open, eyes closed - no difference. I had lost the world.

For eight or nine hours, I writhed in total hallucinated horror. I had lost the world. I had lost David. He was down on the bed somewhere and I was out in madness. There was a door marked "David" that I had closed behind me. The LSD might wear off, but I would not be able to find that door again. I would be out here for ever. Wherever I looked, there would be rippling horror and paralysing fear. For ever.

You had to take acid. I took it eight more times and it was hellish. I took it because that's what you did. You had to break through. Go mad, get out the other side, then really start living. I couldn't seem to get there. I came to the conclusion I was full of terrifying things.

There was another Penguin: The Divided Self by RD Laing. Everyone was reading it. Ronnie Laing said that madness arose in a maddening society. That it was a response to an impossible situation. It was not something to be avoided, it was an essential journey which the therapist must facilitate for the patient so that the patient could emerge whole and healthy on the far side. Madness, then, was a trip. When the book came out in 1965, it was the new rock'n'roll. Innumerable young people who were not mad suddenly wanted to be, it sounded so fascinating and ennobling. The new psychiatry would transform patients into revolutionaries and visionaries. So I wasn't so fucked up. I had embarked on an important trip, but had lost my nerve before getting to the destination.

I rang Laing and made an appointment. He came to the door of his Great Wimpole Street practice in jeans and a brown suede jacket. Jeans - that's cool. We talked about my propensity for fear and horror, and Laing said he would refer me to his colleague, David Cooper. I said, "Does he use LSD?", meaning, "Does he give it to his patients?" Laing said, "Yes, I'm pretty sure David Cooper has taken LSD."

Cooper was born in Cape Town in 1931. He studied medicine at Cape Town University, then left South Africa at the age of 24 and worked in a number of London hospitals. Before taking up private practice, he had presided over Villa 21, a radical treatment unit for schizophrenics, set in the grounds of a larger, mainstream psychiatric hospital. Both Laing and Cooper inclined to a Marxist social analysis. Laing had the more contemplative disposition, while Cooper was actively engaged in the revolutionary applications. Both sought to develop an existential therapy that would enable the patient to acquire an autonomy that did not depend upon the mad reason of the world.

I went to see Cooper twice a week for four years. We started off in Harley Street in 1966. Unlike Laing, Cooper wore a suit. He was a tubby man with a shiny face and a warm, deep voice. His book, Psychiatry And Anti-psychiatry, introduced a key element of the anti-psychiatric position, that there should be no distinction made between doctor and patient. The patient could even treat the doctor and this would be therapeutically most salutary. Such a notion, given the nature of my own anxieties, struck me as rather academic. Besides, Cooper seemed reassuringly sane.

For at least a year, my therapy went well. Cooper was kindly, jolly and wise. I began to learn about projection and to acquire perspective on my fears. Although I was aware of his revolutionary reputation, there were still times when his pronouncements surprised me. On one occasion, he told me a story that may have been designed to dissolve some of the awe that made me feel very much like a patient. As a young man, Cooper had met Jean-Paul Sartre in Paris. The great philosopher proved to be surprisingly approachable, with a marvellous knack of making his admirers feel respected and interesting. That night, Cooper told me, he dreamed that he fucked Sartre up the arse.

As the 60s began to generate heat, I found myself running with a fast crowd. I had moved into a flat near the Royal College of Art, where I attended the film school. I shared the flat with some close friends from Cambridge, including Syd Barrett, who was busy becoming a rock star with Pink Floyd. A few hundred yards down the street, our preternaturally cool friend Nigel was running the hipster equivalent of an arty salon. Between our place and his, there passed the cream of London alternative society - poets, painters, film-makers, charlatans, activists, bores and self-styled visionaries. It was a good time for name-dropping: how could I forget the time at Nigel's when I came across Allen Ginsberg asleep on a divan with a tiny white kitten on his bare chest? And wasn't that Mick Jagger visible through the fumes? Look, there's Nigel's postcard from William Burroughs, who looks forward to meeting Nigel when next he visits London!

As the decade took shape, Cooper abandoned his baggy suit and let his hair grow. As it moved in a Marxian manner towards his shoulders, he took to wearing a black polo-neck sweater and black corduroys. An unflinching rigour compels me to disclose that my therapist also sported a large gold medallion, worn outside his woolly. He left Harley Street and moved to a house off Caledonian Road.

Ever benign and gentle in therapeutic sessions, Cooper started getting himself in the papers for his violent views. At the Dialectics of Liberation Conference, held in the Roundhouse in 1967, he declared that he yearned for the day when "the compassionate chatter of machine guns" might be heard in the streets of north London. This was duly recorded in the evening paper, but they missed the bit right at the end of his speech when he said, "If there is anyone here prepared to die for the Revolution, see me afterwards."

The consulting room in Caledonian Road was painted purple - the colour perceived by infants in utero. Cooper had placed a placard over the fireplace. It bore a quote by Raoul Vaneigem, an impressive situationist writer who had emerged in Paris in 1968: "He who speaks of revolution without living it in their daily life speaks with a corpse in his mouth."

So far, so good. I assumed that therapy had to be like this. These were revolutionary times, after all, and I was keen to keep abreast. I was proud of my therapist. Worlds were going to collapse and he was equipping me for life after death. But he disturbed me in ways that seemed to have no redeeming side. One day in the purple room, he came in, slumped in his armchair and told me he had just been making love to his partner, a feminist writer. "I live within her orgasms," he intoned. "Hmm," I said, nodding. Clearly he had told me something remarkable - you could live within someone's orgasms. But, you know ...

Underlying my discomfort was a fundamental confusion that had come into focus as the 60s progressed: it was considered desirable to have a childlike openness to experience, while at the same time evincing a world-weary, omniscient cool. You'd think I might have been able to relinquish this double bind in an actual therapy session, but although my therapist's frankness continued to upset me, I kept mum. So to speak.

Cooper had been off sick and I'd missed some sessions. When we met again, he had moved to Primrose Hill and I learned what he'd really been up to.

My therapist told me he had been sitting in his kitchen. The bell rings and a dark, beautiful woman asks if she can come in and drop acid with him. Soon they are making love on his bed overlooking the park. As the acid washes in, Cooper and the beautiful woman leave their bodies and assume astral forms, which are radiant and blue. The astral lovers hover above the bed, making divine congress. Then Cooper sees a tunnel - dark, abyssal, falling away before him. He drops down and down, picking up speed.He sees a pale blue disc hurtling towards him. Suddenly he finds himself in... nothing. Not an empty place, but a place of no place, a place beyond spatial ideas. He is suffused with feelings of love. In the distance he sees a low green hill against an azure sky. Standing on the hill is a young boy, his hands outstretched. Falling from the sky, into the boy's hands, is manna. Cooper knows then that we are about to enter a new age. In this age, all institutions will transform into anti-institutions. The power of the state will be overturned as the powerful realise they are interchangeable with the powerless. An era of harshness will be supplanted.

When he came back to his body, Cooper understood that this tearing, heavy world was going to dissolve and, in that knowing, was overcome with relief and sadness. He cried all day for five days. He told me this.

What can you say? You're supposed to be the patient, for God's sake. Do you really want your shrink to be so fascinating? No, you don't. You want him to be reserved, poised in an attentive reverie. You don't want to know about his trips or his girlfriend's orgasms. But isn't that rather pusillanimous of you? I couldn't tell.

The next time I went to Primrose Hill was the night after Cooper had been fucking the dead patient's girlfriend. He had done this, he said, because in her extremity, this was the language that would console her. He said to me, "Perhaps she'd like to sleep with you, David." This was the sort of thing he said.

As well as being naked in the kitchen at Primrose Hill, Cooper had his leg in plaster to the hip. This was because he had fallen down the stairs when pissed. We went next door to the consulting room: Cooper's bedroom. Before the session began, he gave me a fiver, then fell on the bed. Would I go to the off-licence and buy him a bottle of whisky? When I got back, he opened the bottle and offered me some. In those days it was not cool to drink alcohol and I didn't like whisky anyway, so I took half an inch in a plastic cup.

Cooper grasped the bottle and upended it into his mouth. When he had finished, there were a couple of inches left. With difficulty, he rolled across the bed and put the arm of his Philips record player on a track of an album, What Have They Done To My Song, Ma? by Melanie. As she sang out in her tragic American Piaf style, Cooper started to weep. He wept loudly throughout the track and when it was finished, he played it again and wept again. He did this over and over while I sat and watched. After an hour, I decided the session must be over, so I said, "I'd better be going." He did not seem to hear me.

I told myself that my therapist wept because of the melancholy that attends enlightenment. To see the world in its blind, leaden pain had made him heavy-hearted. I'm sure if I'd asked him, he would have said that to be so heavy-hearted is to apply a dreadful stress to one's heart. His heart attack came a few months later. The doctors told him to stop drinking and smoking and taking drugs if he wanted to live more than four months. They gave him drugs of their own, though, seven sorts. These made his hands tremble and purple blisters rise on the backs of his fingers.

I was sitting on the divan talking about my problems. Cooper was smoking, holding a roll-up in his blistered hand. His head was bent in an attentive reverie. I thought I could smell smoke, but not tobacco smoke. "David?" He didn't seem to hear. "David?" Smoke seemed to be rising from his chair. Surely he couldn't be sleeping... Surely the chair... I jumped up. "David!" He groaned and raised his head groggily. "David - the chair's on fire!" He mumbled and struggled to his feet. Smoke billowed from a small inferno in the chair's horsehair stuffing. Cooper had dropped his roll-up. I dragged out a clot of glowing material, stamped on it, then doused the chair with water.

It would be neat to finish there, to say that the patient had saved the analyst, thereby bringing a great circularity and symmetry to the anti-psychiatric process. But while writing this, I remembered that it was not my last session. It took one more to convince me that my analysis was doing more harm than good. I went to see Cooper in a flat in West Hampstead. He was lying on a bed staring emptily past me in a drunken trance. He seemed not to see me. As if I were transparent. I didn't know what to say. Minutes passed as I looked at him and looked away. Then I said, "I must go." Then I left and never went back. I said to myself, "It's fucking me up more staying than going."

In the dedication page of The Death Of The Family, David Cooper wrote, "During the end of the writing of this book against the family, I went through a profound spiritual and bodily crisis that amounted to the death and rebirth experience that I speak of in these pages." The crisis found its peak in his mystical LSD experience with the dark woman and seemed to endure until 1986 when he died of chronic alcoholism.

It was so very hip to be mad in those days; a beatific craziness was to be worn like Tommy Hilfiger. This helped make the 60s exhilarating and revolutionary, while producing a credulous generation intoxicated by relativism. For many, this condition proved impossible to shake off and paved the way for the fog of New Age vagueness, energised by consumerism, that seems to be going global. The extraordinary energy released over 30 years ago has contributed to the state of affairs in which we now have magazines about feng shui and our avant gardists can be identified by the Nike swoosh tattooed on their calves.

These days, madness is to be avoided at all costs - it is neither big nor clever. The energy invested in suppressing madness and chaos sometimes erupts, though. It can produce hysterical displays, such as the Dead Diana festival or the Portsmouth Paedophile rampage. David Cooper knew very well the price to be paid for such a denial and used his own being as a guinea pig for purgation. While the benefits of his wisdom seemed not to avail him personally, it is hard to forget one of his favourite maxims, frequently delivered with a wry chuckle: "If you're going to go mad, then do it discreetly."

David Gale is writing his autobiography. His website can be found at www.iamdavidgale.com.