My first psilocybin journey began around an altar in the middle of a second-story loft in a suburb of a small city on the Eastern Seaboard. On this adventure I would have a guide, a therapist who, like an unknown number of other therapists administering psychedelics in America today, must work underground because these drugs are illegal. Seated across the altar from me, Mary (who asked that I use a nickname because of the work she does) began by reciting, with her eyes closed, a long and elaborate prayer derived from various Native American traditions. My eyes were closed, too, but now and again I couldn’t resist peeking out for a glance at my guide: a woman in her 60s with long blond hair parted in the middle and high cheekbones that I mention only because they would, in a few hours, figure in her miraculous transformation into a Mexican Indian.

I also stole a few glances at the scene: the squash-colored loft with its potted plants and symbols of fertility and female power; the embroidered purple fabric from Peru that covered the altar; and the collection of items arrayed across it, including an amethyst in the shape of a heart, a purple crystal holding a candle, a bowl containing a few squares of dark chocolate, the personal “sacred item” that Mary had asked me to bring (a little bronze Buddha a friend brought me from Tibet) and, set squarely before me, an antique plate holding the biggest psilocybin mushroom I had ever seen.

The crowded altar also held a branch of sage and a stub of palo santo, a fragrant wood that some Indians in South America burn ceremonially, and the jet-black wing of a crow. At various points in the ceremony, Mary would light the sage and the palo santo, using the crow’s wing to “smudge” me with the smoke — guiding the spirits through the space around my head.

The whole scene must sound ridiculously hokey, not to mention laced with cultural appropriation, yet the conviction Mary brought to the ceremony, together with the aromas of the burning plants and the spooky sound of the wing pulsing the air around my head — plus my own nervousness about the journey in store — cast a spell that allowed me to suspend my disbelief. Mary trained under one of the revered “elders” in the psychedelic community, an 80-something psychologist who was one of Timothy Leary’s graduate students at Harvard. But I think it was her manner, her sobriety and her evident compassion that made me feel sufficiently comfortable to entrust her with, well, my mind.

As a child growing up outside Providence, R.I., Mary was an enthusiastic Catholic, she says, “until I realized I was a girl” — a fact that would disqualify her from ever performing the rituals she cherished. Her religiosity lay dormant until, in college, friends gave her a pot of honey infused with psilocybin for her birthday; a few spoonfuls of the honey “catapulted me into a huge change,” she told me the first time we met. The reawakening of her spiritual life led her onto the path of Tibetan Buddhism and eventually to take the vow of an initiate: “ ‘To assist all sentient beings in their awakening and enlightenment.’ Which is still my vocation.”

And now seated before her in her treatment room was me, the next sentient being on deck, hoping to be awakened. She asked me to state my intention, and I answered: to learn whatever the “mushroom teachers,” as she called them, could teach me about myself and about the nature of consciousness.

Psychedelic therapy, whether for the treatment of psychological problems or as a means of facilitating self-exploration and spiritual growth, is undergoing a renaissance in America. This is happening both underground, where the community of guides like Mary is thriving, and aboveground, at institutions like Johns Hopkins, New York University and U.C.L.A., where a series of drug trials have yielded notably promising results.

I call it a renaissance because much of the work represents a revival of research done in the 1950s and 1960s, when psychedelic drugs like LSD and psilocybin were closely studied and regarded by many in the mental health community as breakthroughs in psychopharmacology. Before 1965, there were more than 1,000 published studies of psychedelics involving some 40,000 volunteers and six international conferences dedicated to the drugs. Psychiatrists were using small doses of LSD to help their patients access repressed material (Cary Grant, after 60 such sessions, famously declared himself “born again”); other therapists administered bigger so-called psychedelic doses to treat alcoholism, depression, personality disorders and the fear and anxiety of patients with life-threatening illnesses confronting their mortality.

That all changed in the mid-’60s, after Timothy Leary, the Harvard psychologist and lecturer turned psychedelic evangelist, began encouraging kids to “turn on, tune in and drop out.” Silly as that slogan sounds to our ears, a great many kids appeared to follow his counsel, much to the horror of their parents. The drugs fell into the eager embrace of a rising counterculture, influencing everything from styles of music and dress to cultural mores, and, many thought, inspired the questioning of adult authority that marked the “generation gap.” “The kids who take LSD aren’t going to fight your wars,” Leary famously claimed. In 1971, President Nixon called Leary, who by then had been drummed out of academia and chased by the law, “the most dangerous man in America.” That same year, the Controlled Substances Act took effect; it classified LSD and psilocybin as Schedule 1 drugs, meaning that they had a high potential for abuse and no accepted medical use; possession or sale became a federal crime. (MDMA, which was still being used therapeutically, was not banned until 1985, after it became popular as a party drug called Ecstasy.) Funding for research dried up, and the legal practice of psychedelic therapy came to a halt.

Illustration by Christoph Niemann

But beginning in the 1990s, a new generation of academics quietly began doing psychedelics research again, much of it focusing on people with cancer. Since then, several dozen studies using psychedelic compounds have been completed or are underway. In a pair of Phase 2 psilocybin trials at Hopkins and N.Y.U., 80 cancer patients, many of them terminal, received a moderately high dose of psilocybin in a session guided by two therapists. Patients described going into their body and confronting their cancer or their fear of death; many had mystical experiences that gave them a glimpse of an afterlife or made them feel connected to nature or the universe in a way they found comforting. The studies, which were published in The Journal of Psychopharmacology in December 2016, reported that 80 percent of the Hopkins volunteers had clinically significant reductions in standard measurements of depression and anxiety, improvements that endured for at least six months.

Other, smaller studies of psilocybin have found that one, two or three guided sessions can help alcoholics and smokers overcome their addictions; in the case of 15 smokers treated in a 2014 pilot study at Hopkins, 80 percent of the volunteers were no longer smoking six months after their first psychedelic session, a figure that fell to 67 percent after a year — which is far better than the best treatment currently available. The psychedelic experience appears to give people a radical new perspective on their own lives, making possible a shift in worldview and priorities that allows them to let go of old habits.

Yet researchers believe it is not the molecules by themselves that can help patients change their minds. The role of the guide is crucial. People under the influence of psychedelics are extraordinarily suggestible — “think of placebos on rocket boosters,” a Hopkins researcher told me — with the psychedelic experience profoundly affected by “set” and “setting” — that is, by the volunteer’s interior and exterior environments. For that reason, treatment sessions typically take place in a cozy room and always in the company of trained guides. The guides prepare volunteers for the journey to come, sit by them for the duration and then, usually on the day after a session, help them to “integrate,” or make sense of, the experience and put it to good use in changing their lives. The work is typically referred to as “psychedelic therapy,” but it would be more accurate to call it “psychedelic-assisted psychotherapy.”

Though the university researchers seldom talk about it, much of the collective wisdom regarding how best to guide a psychedelic session resides in the heads of underground guides like Mary. These are the people who, in many cases, continued to do this work illicitly, long after the backlash against psychedelics during the 1960s ended most research and therapy. But their role in the current renaissance is an awkward one, as I discovered early this spring when I sat in on the nation’s first certificate program for aspiring psychedelic guides.

On a Friday afternoon in late March, 64 health care professionals of various stripes — doctors, therapists, nurses, counselors and naturopaths — gathered in Namaste Hall at the California Institute of Integral Studies (C.I.I.S.), a school of psychology and social sciences in San Francisco, to begin their training to become legal psychedelic therapists. To be admitted to the program, an applicant must have a professional medical or therapy license of some kind, and most of the trainees — whose average age looked to be about 45 and whose number included nine psychologists, nine psychiatrists and four oncologists — had enrolled in this certificate program in the belief that psychedelic drugs like psilocybin and MDMA, administered with the proper support and guidance, hold the potential to revolutionize mental health treatment. The career path might not be clear or straight yet, but these people want to be ready to lead that revolution when it arrives — which may be sooner than we think.

It quickly became clear that the reason most of the people in the room were willing to devote the time (five weekends and one full week over nine months) and the money ($7,800) to be certified as a graduate of the program is that they’d been persuaded — often by personal experience — of the therapeutic potential of these compounds. As Manish Agrawal, a rugged 48-year-old oncologist who practices in Maryland, told me, with a sardonic lift of an eyebrow, “You don’t do something like this because you read a magazine article.”

The drugs at the center of the therapy being taught — still classified by the government as Schedule 1 — cannot be used in the training, a limitation that both students and instructors lamented. (C.I.I.S. plans to petition the F.D.A. for permission to give psilocybin and MDMA to students in future trainings.) And while most of the faculty was drawn from the ranks of therapists who work in sanctioned clinical trials of psilocybin and MDMA, because so much of the relevant experience belongs to guides who have been working underground, the program draws on the wisdom of these people too. Though the program’s explicitly stated intention is to train guides to work in the world of legal psychedelic therapy, that world (apart from the handful of clinical trials) doesn’t quite exist yet, while the psychedelic underground beckons right now.

Janis Phelps, a psychologist and C.I.I.S. administrator who established and directs the program, forthrightly confronted the issue in her introductory remarks to the class Friday evening. “We are training you to be aboveground therapists,” she emphasized. “If you are thinking of working underground” — she later told me a strenuous effort had been made to weed out such people — “you need to think about that. Because we want you to be aboveground, F.D.A.-approved therapists. Everyone engaged in this research is squeaky clean.”

She looked out over the room of aspiring guides. “So I invite you into the tensions of the field as it now exists.”

Bill Richards, clinical director of the psychedelics-research program at Johns Hopkins and the author of “Sacred Knowledge: Psychedelics and Religious Experiences,” is one of the few surviving links between the first and second waves of sanctioned psychedelic research in America. A jovial, goateed psychologist in his 70s with an infectious cackle, Richards led off the weekend’s instruction on Saturday morning. Working at the Maryland Psychiatric Research Center at Spring Grove in the 1970s, Richards and his colleagues successfully treated alcoholics, cancer patients and people suffering from depression with LSD until 1976, when research at the center shut down. “How can this ever have been illegal?” Richards likes to say. “It’s as if we made entering Gothic cathedrals illegal, or museums, or sunsets!”

When research with psilocybin resumed in the 1990s, Johns Hopkins recruited Richards because of his long experience guiding patients during a high-dose psychedelic experience. Today’s researchers work with psilocybin and MDMA because a session tends to be shorter than with LSD and because the words carry much less political baggage. Since the ’60s, LSD has been associated in the public mind with the counterculture and with stories, true or not, of people jumping off buildings thinking they could fly, blinding themselves by staring at the sun or landing themselves in the emergency room after psychotic episodes. MDMA and psilocybin are less well known and don’t seem to have the same associations. (Also, the fact that psilocybin is “natural” — derived from a mushroom — seems to count in its favor.) Richards has trained many of the guides now working in clinical trials not only at Hopkins but also at N.Y.U. and at Imperial College London.

In his PowerPoint presentation, Richards laid out what has become the standard protocol for aboveground psychedelic therapy, and the role of the guide at each of the three principal stages of “the journey.” First comes a series of preparation sessions, in which volunteers are told what to expect, asked to set an intention (to quit smoking, say, or confront their fear of death) and offered a set of “flight instructions” for the journey ahead. These generally advise surrendering to the experience, whatever it brings and however disturbing it might become. (“Trust, let go, be open” is one mantra he recommends, or, borrowing from John Lennon, “Turn off your mind, relax and float downstream.”) If you feel as if you are “dying, melting, dissolving, exploding, going crazy, etc. — go ahead.” Richards stressed how important it is for the guide to quickly establish a rapport with volunteers, so that during the session “they can let themselves ‘die’ or go crazy — that requires an awful lot of trust!” Because the patients’ ego defenses are likely to be disabled by the drug, it’s crucial that they feel safe.

The second stage is the journey itself. Richards showed a slide of the Hopkins treatment room, decorated to look like the office of a psychiatrist with an interest in Eastern religion and indigenous peoples, with shelves holding large-format art books and spiritual tchotchkes, including a Buddha and a large ceramic mushroom. The volunteer stretches out on a couch and puts on eyeshades and headphones to encourage an inward journey free of distraction. (Richards has put together a playlist consisting mainly of classical compositions arranged to support and structure the experience.) Two guides, typically one male, the other female, sit with the volunteer for the duration but say very little, allowing the journey to unfold according to its own logic. Mostly the guide is present to offer a comforting hand if the journeyer is struggling, jot down anything she has to say and generally keep an eye on the volunteer’s physical well-being while she is roaming her psychic landscape. Because it is the drug and the mind that drive the journey and not the therapist, the guide’s role calls for an unusual degree of humility, restraint and patience — the sessions can last for hours. (No snoozing or checking of email; meditating, however, is O.K.) Richards describes the session as the “pièce de résistance” of the work, “in which you’re focused intensely on one human being as if that’s all that exists in the world. It’s a great way to get exhausted!”

The last stage is integration, which typically takes place the following day. Here the guide helps the volunteer make sense of what can be a confusing and inchoate experience, underscoring important themes and offering ideas on how to apply whatever insights may have emerged to the conduct of the volunteer’s life. The challenge, as Richards put it, is to help the volunteer transform “flashes of illumination” (he’s quoting Huston Smith, the late scholar of religion) experienced during the trip “into abiding light” — into a new, more constructive way to regard your self and situation.

It is sometimes said that in the last few decades psychiatry went from being brainless — relying on talk therapies oblivious to neurobiology — to being mindless — relying on drugs, with little attention to the contents of consciousness. If psychedelic-assisted therapy proves as effective as early trials suggest it might, it will be because it succeeds in rejoining the brain and the mind in a radical new therapeutic paradigm: using not just a chemical but the powerful mental experience it can occasion, given the proper support, to disrupt destructive patterns of thought and behavior.

Such a new approach couldn’t come at a better time for a field that is “broken,” as Tom Insel, head of the National Institute of Mental Health until 2015, told me bluntly. Rates of depression (now the leading cause of disability worldwide, according to the W.H.O.) and suicide are climbing; addictive behavior is rampant. Little has changed, meanwhile, in psychopharmacology since the introduction of SSRI antidepressants in the late 1980s. This may explain why prominent figures in the psychiatric establishment are voicing support for psychedelic research. Addressing a conference on psychedelic science in Oakland last spring, Insel and Paul Summergrad, a former president of the American Psychiatric Association, offered encouragement to the psychedelic researchers in the audience, with Insel singling out for praise “the novel approach here” — the way the psychedelic therapist combines pharmacology and psychotherapy to create a single transformative experience.

Psychedelic therapy as the idea is now understood was developed by a group of researchers working in Saskatchewan in the mid-1950s, including the psychiatrists Abram Hoffer, Humphry Osmond (who, in 1957, coined the word “psychedelic,” which loosely translates from the Greek as “mind manifesting”) and their frequent collaborator and muse, a brilliant amateur therapist named Al Hubbard. After both conducting and participating in a great many mescaline and LSD sessions — at the time it was routine for scientists to test drugs on themselves — the researchers observed how variable the experience could be, depending on circumstance and mind-set. In those days, no one knew how best to administer these strange new compounds; the need for a guide wasn’t immediately apparent. Some early scientists in white coats bearing clipboards dosed volunteers in a hospital room with white walls and fluorescent lights. Very often, the volunteers would then be left alone. Researchers didn’t yet understand that the psychedelic experience is not foreordained by the chemical but rather is “constructed” in the mind from an unpredictable mix of expectation, memory, the contents of the unconscious and a variety of environmental factors.

Beginning in the late 1950s, as the researchers began to better grasp the many factors at work, they began to work more consciously with set and setting (though the words wouldn’t be used for another few years), bringing music and images into a treatment room they made comfy and emphasizing the role of a guide. Shamans have known for thousands of years that a person in the depths of a trance or under the influence of a hallucinogenic plant like ayahuasca or peyote can be readily manipulated with the help of certain words, cues, special objects or music. They understand intuitively how the suggestibility of the human mind during an altered state of consciousness can be harnessed as an important resource for healing — for breaking destructive patterns of thought and proposing new perspective in their place. One of the Canadian group’s key contributions to psychedelic therapy was to introduce the tried-and-true tools of shamanism, or rather the Westernized version of it that, to one degree or another, most of today’s psychedelic guides still practice, whether working aboveground or below — though the tools of shamanism play a larger role in the underground.

Illustration by Christoph Niemann

Before my own psychedelic journey, I met and interviewed more than a dozen such guides, many of them trained by the therapists who were using psychedelics in their practices before they became illegal and decided that, rather than give up a tool they had found to be effective, they would continue to work underground, at substantial personal risk. (Beginning in 1971, possession or sale of most psychedelic drugs was punishable by a prison sentence.) One such therapist was a Bay Area Jungian psychologist named Leo Zeff, perhaps the best-known underground guide of his generation; before his death in 1988, he claimed to have “tripped” 3,000 patients and helped train 150 underground guides, many of whom are still at work.

My travels through the psychedelic-therapy underground convinced me that while the community is obviously far-flung and heterogeneous and has its complement of charlatans, many guides are professionals who share an approach and even a code of conduct. In 2010, a “wiki” for guides appeared on the internet — a collaborative website where individuals could share documents and together create new content — where, for a time, the community appeared to be codifying the rules and standards of the profession. (The site has since vanished or moved.)

On the website, I found a draft charter for would-be guides — “to support a category of profound, prized experiences becoming more available to more people” — as well as links to printable forms for legal releases, ethical agreements and medical questionnaires. (“We don’t have very good insurance,” one guide told me. “So we’re very careful.”) There was also a link to a thoughtful “Code of Ethics for Spiritual Guides,” which acknowledges that “participants may be especially open to suggestion, manipulation and exploitation.” The code stresses that it is incumbent upon the guide to disclose all the psychological and physical risks. (Compared with other psychoactive compounds, psychedelics have low toxicity and are nonaddictive. The risks are primarily psychological: In some people, they can produce short-term anxiety and paranoia and, in rare cases, psychotic episodes. In the current clinical work, an estimated 1,000 volunteers have received psilocybin without a single serious adverse event.) The code also requires that the guide obtain consent, guarantee confidentiality, protect the safety of participants at all times, “safeguard” against ambition and self-promotion and accommodate clients “without regard to their ability to pay.”

Relative to the way guiding is practiced in the aboveground clinical trials (and taught at C.I.I.S.), the underground guides I interviewed, and eventually worked with, take a somewhat more active role in choreographing the experience, bringing into the “ceremony,” as they’re apt to call it, such traditional elements as incense, tobacco and sage smoke, rattles, the singing of icaros (sacred songs) and chanting of prayers.

“There are now two distinct lineages,” I was told by an underground guide with 35 years of experience, who asked me to use a family name, Michelle. “In the Western medical model, the guide is taught never to ‘get ahead of the medicine’ ” — that is, he or she aims for a noninterventionist, back-seat role during the session, and because these are foremost scientific trials, sticks to a standardized protocol in order to minimize the number of experimental variables in play. Many underground guides find this needlessly confining.

“The journey should be customized to each person,” Michelle said. “The idea of playing the same music for everyone makes absolutely no sense.” Instead, she might choose a comforting piece to support someone struggling with a challenging trip, or put on something “chaotic and disassembling” to help break down another client’s defenses. “A healer is not just a sitter. She does stuff.” Many underground guides have traveled extensively in Mexico, Brazil and Peru to study with traditional healers; Michelle believes psychedelic therapy still has much to learn from the “earth peoples” who have made use of psychedelic plants and fungi in their healing ceremonies for thousands of years. She feels the work she does offers more scope for “creativity and intuition” than the rote clinical techniques being taught aboveground allow.

I would have preferred to have my own guided psilocybin session aboveground in the reassuring confines of a medical institution, but the teams at Hopkins and N.Y.U. weren’t currently working with so-called healthy normals (do I flatter myself?) — and I could lay claim to none of the serious mental problems they were studying. I wasn’t trying to fix anything big — not that there wasn’t room for improvement. Like many people in late middle age, I had developed a set of fairly dependable mental algorithms for navigating whatever life threw at me, and while these are undeniably useful tools for coping with everyday life and getting things done, they leave little space for surprise or wonder or change. After interviewing several dozen people who had undergone psychedelic therapy, I envied the radical new perspectives they had achieved. I also wasn’t sure I’d ever had a spiritual experience, and time was growing short. The idea of “shaking the snow globe” of my mental life, as one psychedelic researcher put it, had come to seem appealing.

In Mary, I had found an underground guide with whom I felt comfortable. Mary’s approach, in terms of dosage, also happened to approximate the aboveground experience, though she worked with whole mushrooms rather than the capsules of synthetic psilocybin used in the university trials.

“The mushroom teachers help us to see who we really are,” Mary said, as we sat across the altar from each other. “They bring us back to our soul’s purpose for being here in this lifetime.” By now I was inured to the New Age lingo. I was also impressed, and reassured, by Mary’s professionalism. In addition to having me consent to the standard “agreements” (bowing to her authority for the duration; remaining in the room until she gave me permission to leave; no sexual contact), she had me fill out a detailed medical form, a legal release and an autobiographical questionnaire that resulted in 15 pages of writing it took me the better part of a day to complete. All of which made me feel I was in good hands, even when those hands were flapping a crow’s wing around my head.

On my tongue, the dried mushroom, which was easily four inches long and had a cap the size of a golf ball, was as parched as desert sand and tasted like earth-flavored cardboard, but alternating each bite with a nibble of chocolate helped me get it down. We chatted quietly for 20 minutes or so before Mary noticed that my face was flushed and suggested I lie down and put on eyeshades. As soon as Mary put on the first song — an insipid New Age composition by someone named Thierry David (an artist thrice nominated, I later learned, in Zone Music Reporter’s category of Best Chill/Groove Album) — I was immediately propelled into a nighttime urban landscape that appeared to have been generated by a computer.

I was experiencing synesthesia, in which one sense gets crosswired with another, so that sound was creating visual space, and what I took to be David’s electronica conjured a depopulated futuristic city, with each note giving rise to another soft black stalagmite or stalactite that together resembled the high-relief soundproofing foam used to line recording studios. I moved effortlessly through this digital nightscape as if within the confines of a dystopian video game. Though the place wasn’t particularly frightening and had a certain sleek beauty, I hated being in it and wished to be somewhere else, but it went on and on, seemingly forever. I asked Mary to please play something else, and though the mood shifted with the new music, I was still stuck — trapped — in this sunless computer world. Why, oh why, couldn’t I be outside?

This could easily take a terrifying turn, it occurred to me, and with that a dim tide of anxiety began to build. Recalling the flight instructions, I told myself there was nothing to do but let go and surrender to the experience. Relax and float downstream. I realized I was no longer captain of my attention, able to direct it this way or that and change the mental channel at will. No, this was more like being strapped into the front car of a cosmic roller coaster, its heedless headlong trajectory determining moment by moment what would appear in my field of awareness.

Actually, that’s not entirely true: All I had to do was remove my eyeshades, and reality, or at least something loosely based on it, would re-present itself. This is what I now did, partly to satisfy myself that the world still existed but mostly because I badly needed to pee. Sunlight and color flooded my eyes, and I drank it in greedily, surveying the room for the welcome signifiers of nondigital reality: walls! Windows! Plants! But this reality appeared in a new aspect: jeweled with morning light, every beam of it addressed to my eyes. I got up carefully from the mattress, and Mary took me by the elbow, geriatrically, and together we made the long journey across the loft to the bathroom. I avoided looking at her, uncertain what I might see in her face or betray in mine.

After producing the most spectacular crop of diamonds, I made my unsteady way back to the mattress and lay down. Mary, speaking softly, asked if I wanted “a booster.” I sat up to receive another mushroom, for a total of about four grams. Mary was kneeling next to me, the mushroom in her upturned palm, and when I finally looked up into her face, I saw she had turned into María Sabina, the Mazatec curandera whom I had read about. Sixty years ago, Sabina gave psilocybin mushrooms to R. Gordon Wasson, supposedly the first Westerner to try them, in a dirt-floored basement of a thatch-roofed house in the remote mountains of Oaxaca. Mary’s hair was now black; her face, stretched taut over its high cheekbones, was anciently weathered; and she was wearing a simple white peasant dress. I took the desiccated mushroom from the woman’s wrinkled brown hand and looked away as I chewed; I didn’t think I should tell Mary what had happened to her.

When I put my eyeshades back on and lay down, I was disappointed to find myself back in computer world, but something had changed, no doubt a result of the stepped-up dose. Whereas before I navigated this landscape as myself, taking in the scene from a perspective recognizable as my own, with my attitudes intact (highly critical of the music, for instance), now I watched as that familiar self began to fall apart before my eyes, gradually at first and then all at once.

“I” now turned into a sheaf of little papers, no bigger than Post-its, and they were being scattered to the wind. But the “I” taking in this seeming catastrophe had no desire to chase after the slips and pile my old self back together. No desires of any kind, in fact. And then I looked and saw myself out there again, but this time spread over the landscape like paint, or butter, thinly coating a wide expanse of the world with a substance I recognized as me.

But who was this “I” that was able to take in the scene of its own dissolution? Good question. It wasn’t I, exactly. Here the limits of our language become a problem: In order to completely make sense of the divide that had opened up in my perspective, I would need a whole new first-person pronoun. For what was observing the scene was a vantage and mode of awareness entirely distinct from my accustomed self. Where that self had always been a subject encapsulated in this body, this one seemed unbounded by any body, even though I now had access to its perspective. That perspective was supremely indifferent, unperturbed even in the face of what should have been an unmitigated personal disaster. The very category “personal,” however, had been obliterated. Everything I once was and called me, this self six decades in the making, had been liquefied and dispersed over the scene. What had always been a thinking, feeling, perceiving subject based in here was now an object out there. I was paint!

Lots of other things happened in Mary’s room, and in my head, during the course of my journey that day. I gazed into the bathroom mirror and saw the face of my dead grandfather. I trudged through a scorched desert landscape littered with bleached bones and skulls. One by one appeared the faces of the people in my life who had died, relatives and friends and colleagues whom, I was being told, I had failed properly to mourn. I beheld Mary transformed once again, this time into a ravishing young woman in the full radiance of youth; she was so beautiful I had to turn away.

Illustration by Christoph Niemann

At one point Mary put on one of Bach’s unaccompanied cello suites. It was the suite in D minor, a spare, infinitely sad piece that I’d heard many times before, often at funerals. But this time was different, because I heard it in my egoless, nondual state of consciousness — though “heard” doesn’t do justice to what transpired between Bach’s notes and me. The preposition “between” melted away. Losing myself in the music became a kind of rehearsal for losing myself, period. I let go of the rope of self and slipped into the warm waters of this ineffable beauty — Bach’s sublime notes, I mean, drawn from a cello’s black well of space by Yo-Yo Ma’s mournful bow as it surfed across its strings. I became identical to the music, a word that doesn’t begin to describe the power of what these unearthly vibrations were, or explain how they somehow lifted up and carried me beyond the reach of all suffering and regret.

The sovereign ego, with all its armaments and fears, its backward-looking resentments and forward-looking worries, was simply no more, and there was no one left to mourn its passing. And yet something had succeeded it: this bare, disembodied awareness, which gazed upon the scene of the self’s dissolution with benign indifference. I was present to reality but as something other than my usual self. And although there was no self left to feel, exactly, there was a feeling tone, and that was calm, unburdened, content. There was life after the death of the ego.

The Sunday-morning session at C.I.I.S. began with great anticipation — the speaker was Ralph Metzner, who worked with Timothy Leary at Harvard and is regarded as one of the wise elders in the psychedelic community.

Metzner is in his 80s now, and stepping up to the microphone in his newsboy’s cap, he seemed frail. For much of his presentation, he read from one of his books — something about the soul and the six archetypal paths through this life. It wasn’t until the Q. and A. that things got interesting.

A student who identified himself as a psychotherapist asked Metzner to talk about psychedelics, a subject he hadn’t yet mentioned. With that gentle nudge, Metzner proceeded to veer wildly off message, exposing the tensions that Janis Phelps alluded to Friday night but that had been absent from the weekend’s presentations thus far. “These are drugs that psychotherapists unanimously feel could improve psychotherapy,” Metzner began, “but their use is illegal. What does that tell you? Something about the society we live in!”

Metzner paused — and then jumped. “There is a vast underground network of psychedelic therapy, you know — vast. Larger than the approved uses of psychedelic therapy.” He went on: “It’s an underground culture, and underground cultures are good, in fact they can be lifesaving.” Phelps, her porcelain complexion reddening, stood up, taking a step toward the lectern to solicit another question, but Metzner wouldn’t be deterred. Declaring that we were in the midst of a spiritual emergency in this country, he told the students we have these “fantastically promising medicines that can cure all sorts of ills, and yet doctors can’t get them.”

Metzner’s voice rose. “We don’t have to accept that!” The eminent professor seemed to be inviting his flock to engage in a collective act of civil disobedience. This he likened to the underground in Germany, where he grew up, during the war: “There were German families who took in Jewish families and hid them in their closets.” He voiced impatience with the pace of scientific research and federal approval, “at a time of civilizational collapse,” when we have these medicines that we know work and could help our society right now. “It doesn’t need to be proven over and over again. When there’s a plague, you don’t go through double-blind placebo-controlled studies! It’s a plague!”

Finally it fell to Bill Richards to stand up and gently remind the students that while the pace of progress might be frustrating, “we have a path forward” — the path of sanctioned clinical trials leading to approval of psychedelic therapy. He pointed out that the researchers on this path had so far found federal regulators to be remarkably open and receptive. “So let’s go forward as scientist-warriors and do what we can in the aboveground world. I think we can make a significant impact.”

The students I spoke to afterward clearly shared Metzner’s sense of urgency and frustration, but they rejected his apparent invitation to join the underground. In their view, Metzner was looking backward, to a dark age when the underground served as the saving ark of psychedelic therapy. But that dark age was drawing to a close, they believed. A generation or two younger than Metzner, these people were looking resolutely forward — to a time, not too distant they thought, when the F.D.A. would approve the therapeutic use of psilocybin and MDMA and make them available to doctors to prescribe to their patients. This was the future they had signed up for when they enrolled in the course.

One student in the class, a psychiatrist who had participated in psychedelic therapy in South America for decades, told me after the session that she was now fully committed to the legal road. “I’ve had a secret life for 30 years,” she said. “I damn well want this opportunity to unify my life. Because of this class, I have a way to talk openly to people about psychedelics for the first time.” She voiced deep respect for Metzner but believed the time had come to make a choice. “I don’t want to lose the history or the knowledge we’ve gained from the underground work. But the professionals in this room have decided to put our time and credentials into furthering the legal use of these medicines.” Doing so, she said, “demands being beyond reproach so as not to endanger the work and the path that has been set out.”

Manish Agrawal, the Maryland oncologist, expressed the general sentiment in an email he sent me after Sunday’s session. He shared Metzner’s “frustration that this therapy isn’t available for my patients today, and many will suffer and die without access to this therapy. Ralph really pushed me to feel the injustice of that.” He went on: “But everyone senses how close we are,” and doesn’t want to jeopardize that by following Metzner off the legal route. Agrawal left San Francisco determined to find a way to incorporate psychedelic therapy in his oncology practice.

The day after my journey, I was grateful for the opportunity to return to Mary’s room for a couple of hours of “integration.” Without it, people might be tempted to dismiss their psilocybin journeys as simply a “drug experience,” put it in that handy box and throw it away; this has no doubt been the fate of a great many psychedelic trips. Yet though it is true that a chemical started me on this journey, it is also true that everything that I experienced I experienced: These are events that took place in my mind, psychological facts that were neither weightless nor evanescent. But I needed help making sense of them and putting them to use.

That I could survive the dissolution of my ego and its defenses was surely something to be grateful for, and we talked at length about this. What a remarkable gift: to learn that we can let go of so much — the desires, fears and defenses of a lifetime! — without suffering complete annihilation. This might not come as a surprise to Buddhists or serious meditators, but it was news to me, who had never felt anything but identical to my ego. Could it be that there is another ground on which to plant our feet? For the first time, I began to understand what the volunteers in the cancer-anxiety trials were telling me — how it was that a single psychedelic journey granted them a perspective from which the very worst life can throw at us could be regarded objectively and accepted with equanimity. I had been given a glimpse of that liberating perspective.

“That alone seems worth the price of admission,” Mary offered, and I had to agree. I also realized that I never would have achieved that perspective had Mary not guided me, creating a space where I felt safe enough to let go of my accustomed self and its usual defenses.

Yet 24 hours later, my old ego was back in uniform and on patrol, so what long-term good was that beguiling glimpse of a loftier perspective? Mary suggested that, having had a taste of a different, less defended way to be, I might learn to relax the ego’s trigger-happy command of my reactions to people and events. “Now you have had an experience of another way to react — or not react. That can be cultivated.” She suggested meditation as one way to do that.

Many researchers believe that the experience of “ego dissolution” that I had in Mary’s room can disrupt destructive patterns of thought and behavior and open us to new perspective from which to view death or addiction or depression. This was understood back in the 1950s and ’60s, when psychiatrists working with psychedelics sometimes described it as “therapy by self-transcendence.”

If the ego can be said to have an address, it would probably be in something called the default mode network, a high-level hub in the brain linking the frontal cortex to older centers of memory and emotion. The D.M.N. appears to be involved in a range of operations related to our sense of self, like rumination, time travel (contemplating the past and future), theory of mind (the ability to impute mental states to others) and the so-called autobiographical self: It helps us integrate whatever’s happening to us now with the story of who we are, thereby giving us an abiding sense of a self that is consistent over time. Neuroscientists recently began imaging the brains of people on psilocybin or LSD, and they were surprised to find that, rather than increasing brain activity, as you might expect, the drugs radically quieted traffic in the D.M.N. In particular, when volunteers report the experience of ego dissolution, their brain imaging shows a precipitous drop in D.M.N. activity.

Taking this network temporarily offline may allow the whole system to “reboot,” in the words of Robin Carhart-Harris, a pioneering neuroscientist who has done extensive work imaging tripping brains at Imperial College London. The “loosening of cognition” that results, he says, is especially helpful to people suffering from the varieties of mental stuckness, including depression, addiction, anxiety and obsession.

Illustration by Christoph Niemann

All these conditions, as Alison Gopnik, a professor of psychology at Berkeley, points out, may share an etiology. “There are a range of difficulties and pathologies in adults, like depression, that are connected with the phenomenology of rumination, and an excessively narrow, ego-based focus,” says Gopnik, whose research explores the consciousness of children, which she believes bears a similarity to psychedelic consciousness. “You get stuck on the same thing, you can’t escape, you become obsessive, perhaps addictive. It seems plausible to me that psychedelic experience could help get us out of those states, create an opportunity in which the old stories of who we are might be rewritten.”

Just how soon might psychedelic-assisted psychotherapy be available aboveground, to the many people who stand to benefit from it? Before the F.D.A. approves a new medicine, the drug must survive testing for safety and efficacy in a three-stage sequence of trials, each of them involving a larger sample and more rigorous methods. When researchers recently brought to the F.D.A. the results of Phase 2 clinical trials of cancer patients who were given psilocybin and MDMA, they were stunned by the positive response of the regulators. Regulators told them they could move forward to Phase 3 with MDMA, the last step before F.D.A. approval. The F.D.A. is still considering when psilocybin trials can move into Phase 3. The agency wouldn’t comment on drugs in the approval process, but a researcher who attended one of these meetings told me the regulators seemed untroubled by the illicit status of the drugs in question or by the unique challenges of controlling studies of psychedelics. These meetings took place before a Trump-appointed F.D.A. commissioner was sworn in; it remains to be seen how the Justice Department under Jeff Sessions would respond to F.D.A. approval of psychedelics. The researchers felt heartened by the F.D.A.’s response. The message the scientists took away from the meeting was that they should raise their sights and not limit themselves to treating cancer patients, but rather test the drugs on the much larger population of patients suffering from major depression.

Thus encouraged, the Multidisciplinary Association for Psychedelic Studies (MAPS), a nonprofit that has been working for federal approval of psychedelics since 1986, will begin Phase 3 trials of MDMA-assisted psychotherapy this summer for the treatment of post-traumatic stress disorder, involving more than 200 volunteers at 16 sites in the United States, Canada and Israel. Later this year, pending F.D.A. approval, two Phase 3 trials of psilocybin — one for the treatment of major depression and the other for “psychospiritual distress” in cancer patients — are expected to get underway at Hopkins, N.Y.U. and a half-dozen other sites around the country.

Phase 3 trials, which typically involve hundreds of subjects at dozens of sites, can cost tens of millions of dollars — a cost ordinarily borne by the big pharmaceutical companies that stand to profit from approval. But Big Pharma has not demonstrated significant interest in psychedelics, and it’s not hard to see why: Psychedelic therapy is a rather square peg to fit into the round hole of psychopharmacology as we now know it. Patents on the molecules in question — LSD, psilocybin and MDMA — have long since expired (psilocybin comes from a common mushroom); the drugs, if approved, don’t need to be taken more than a few times; and as the C.I.I.S. program recognizes, psychedelic-assisted psychotherapy is a novel hybrid of pharmacology and talk therapy, making it uncharted territory for a pharmaceutical industry organized around the selling of pills.

But the obstacle of funding Phase 3 trials appears to have been recently surmounted. The Psychedelic Science Funders Collaborative (P.S.F.C.), a new Bay Area-based consortium of philanthropists including the hippie-soap entrepreneur David Bronner, the author and tech investor Timothy Ferriss and other donors both in and out of the tech community, has helped raise more than $63 million in charitable contributions, an amount that could be sufficient to complete the trials. The two main beneficiaries of these funds will be MAPS and Usona Institute, a nonprofit medical-research organization that is sponsoring forthcoming psilocybin trials. Rebekah Mercer, the Trump funder behind Cambridge Analytica and Breitbart, is also a donor to MAPS.

There is at least one corporation betting that psychedelic therapy will soon become a business. Founded in London by George Goldsmith, a health care industry consultant, and Ekaterina Malievskaia, a physician, Compass Pathways aims to become the world’s first psychedelic pharmaceutical company. (The couple, who are married, were inspired to expand access to psilocybin after Malievskaia’s college-age son was successfully treated by an underground guide with the drug for a debilitating case of depression.) Compass aims to be much more than a drug company, however. The company is developing a complete treatment package — consisting of a training program for therapists; protocols for orchestrating the entire experience; and the medicine itself — that it hopes to sell to health care institutions and national health services, first in Europe and then in the United States.

Its initial therapeutic target is treatment-resistant depression (patients who have failed to respond to at least two previous treatments); after an advisory process with the European Medicines Agency (the E.U.’s drug-regulating body), it has decided to conduct trials in eight to 10 sites across Europe. It is also in discussions with the F.D.A. to organize trials here. According to Goldsmith, Compass has already raised $13 million from investors in the United States and Europe, many of them from the tech community (Peter Thiel is an investor) but also institutional investors in the health care sector.

Phase 3 trials will take at least three years, but access to psychedelic therapy could come sooner than that. Under “expanded access” or “compassionate use” programs, patients who stand to benefit from therapies still deemed experimental can gain access to them before trials are complete. In the case of MDMA, this could happen as soon as 2020.

That tantalizing possibility is very much on the minds of the C.I.I.S. students. On the flight home, Manish Agrawal and his oncology partner Paul Thambi began planning how to talk to their colleagues about the idea of adding psychedelic therapy to their practice, and where in their offices they might create a treatment room. Did they plan to hire guides to conduct the sessions? Perhaps, they said, but the weekend had left them both convinced this was work they very much wanted to do themselves.

“We don’t die well in this country,” Agrawal told me during a lunch break at the weekend course. “And we have pretty limited tools to help people deal with their fear. Prozac doesn’t work. The issue isn’t depression; it’s facing your mortality.” The oncologists’ commitment to training as psychedelic guides is notable; they would most likely be able to prescribe psilocybin once it’s approved without years of experience, a prospect that concerns some of the underground guides I interviewed. “Just because you have the ability to prescribe,” one guide told me, “doesn’t mean you have the wisdom to guide the experience.”

In the wake of the weekend’s high hopes, I couldn’t help wondering what the brave new world of legal psychedelic therapy might mean for guides like Mary and Michelle. I had heard some grumbling in the community about the limitations of the C.I.I.S. training, and the bitter twist that the psychedelic guides with the deepest experience could be excluded in favor of newly credentialed guides with no real-world experience whatsoever.

But Michelle said she is busier than ever. Mary, too, anticipates that federal approval of psychedelic medicine would bring more people to her door, especially those without an obvious pathology — the curious, the spiritual seeking and the legions of run-of-the-mill neurotics who already fill therapists’ offices. How many of them will want to try a guided psychedelic journey once they hear about it?

“I don’t think it’s going to hurt me at all,” Mary told me. “If anything, it will allow me to do even more than I do.” Was she worried about a crackdown if psychedelic therapy suddenly becomes fashionable? The work was too important to let that stop her. “I need to find a way to continue to protect myself, as I help people find their soul’s purpose in this lifetime, to help them awaken.”