Richards’s convictions, and his aspirations for psychedelics, prompt questions about the objectivity of such research. Rick Strassman, a psychiatrist at the University of New Mexico who conducted psychedelic research in the early nineties, suggested to me that at least some of the researchers came to the study with “a mission” to demonstrate the spiritual and psychological value of psilocybin. He pointed to the risk of selection bias: those who volunteer are likely to be “spiritually hungering for a mystical experience,” which increases the chance that they will have one. “I would not think that a stodgy Talmudic scholar would want to participate,” he told me. “For them, it’s the word and the law. Spiritual experience alone is not that important.” In 2020, Matthew Johnson, a Johns Hopkins researcher and a co-author of the religious-leaders study, made similar warnings in an article titled “Consciousness, Religion, and Gurus: Pitfalls of Psychedelic Medicine.” He wrote of “scientists and clinicians imposing their personal religious or spiritual beliefs on the practice of psychedelic medicine.”

When Priest stepped into the psychedelic-session room at Johns Hopkins, he felt both excited and anxious. The vibe of the space was more living room than clinic; it had a cozy couch for participants to lie on, vaguely spiritual-looking art work on the walls, and a small statue of the Buddha on a bookshelf. Richards, who has a wide, toothy grin, was one of two facilitators, or “guides,” present to supervise the experience. Priest told me that, before he took the blue capsule that Richards offered him in an incense burner shaped like a chalice, he admitted to feeling nervous. He couldn’t recall exactly what Richards said in response, but he remembered the message that he received: You should be nervous. You’re about to meet God.

The cross-pollination of religion and psychedelics has a long history. In the psychedelic community, it is virtually an article of faith that hallucinogenic plants and fungi played a role in the visions and mystical experiences that helped give rise to some religions. The Eleusinian Mysteries, the annual rite honoring Demeter that was performed in Greece for nearly two thousand years, climaxed with the consumption of a potion called the kykeon, which was said to give participants visions of the afterlife and enable them to commune with their ancestors. Albert Hofmann, the Swiss chemist who discovered LSD, in 1938, suspected that the recipe included ergot, the fungus on which his discovery was based. (Demeter is the goddess of agriculture and fertility; ergot grows on grain.)

In the New World, peyote, psilocybin mushrooms, and the seeds of the ololiuqui—a type of morning glory—have had sacramental uses for millennia. In the early aughts, scientists dated two specimens of peyote, found in a cave near the Rio Grande, at more than five thousand years old. After Spanish colonizers arrived, the Catholic Church banned the use of mushrooms in Aztec rituals; the Nahuatl word for them—teonanácatl—translates roughly as “flesh of the gods,” which must have sounded like a direct challenge to the Christian sacrament. The practice continued underground, however, and similar customs persist today.

The U.S. banned peyote in the late nineteenth century, but the Native American Church, which fuses Indigenous and Christian beliefs, fought a prolonged legal and legislative battle for the right to use the peyote cactus in its ceremonies. The effort ended successfully in 1993, when Congress passed the Religious Freedom Restoration Act. Since then, two churches that originated in Brazil have secured the right to use ayahuasca during ceremonies in the U.S. Psychedelic churches, some sincere in their spiritual convictions and others not so much, are opening at an accelerated rate. Lawyers in the newly formed Psychedelic Bar Association say that this trend has been encouraged by the Supreme Court’s expansive approach to religious liberty.

In 1962, Walter Pahnke, a Harvard graduate student who studied under the psychologist and psychedelic advocate Timothy Leary, administered either a pill containing psilocybin or a placebo to twenty volunteers, mostly Protestant divinity students. The volunteers then sat in the basement of Marsh Chapel, at Boston University, and listened to a Good Friday sermon piped in from the pulpit above them. Of the ten volunteers who received the drug, eight reported powerful mystical experiences. In the placebo group, one did. The researchers’ definition of mysticism mirrored the one in “The Varieties of Religious Experience,” a 1902 collection of lectures by the psychologist and philosopher William James, who experimented with nitrous oxide. James associated mystical experiences with a sense of well-being, timelessness, ineffability, and unity with “ultimate reality.”

Pahnke’s published research failed to mention that, as participants recalled years later, one person fled the chapel and headed toward Commonwealth Avenue, possibly to spread the word of Jesus to passersby; he had to be restrained and given an injection of the antipsychotic Thorazine. Another participant, Huston Smith, was a leading scholar of religion. “Until the Good Friday Experiment,” he told an interviewer in 1996, “I had had no direct personal encounter with Him/Her/It.”

Griffiths, Richards, and their colleagues were inspired in part by the Good Friday Experiment. In a study published in 2006, they administered psilocybin to several dozen volunteers, who then filled out surveys that included a “Mystical Experience Questionnaire.” The questionnaire drew on Pahnke’s experiment and James’s writings. The researchers ultimately concluded that psilocybin could reliably occasion mystical experiences.

Priest’s psychedelic journey at Johns Hopkins followed norms that have become common in modern psychedelic research: After several preparatory sessions with two guides, the participant swallows the capsule, lies down on a couch, and dons a pair of headphones and an eye mask, to encourage an inward focus. The facilitators say little, but share words of advice or comfort if the experience turns frightening; “in and through” is a common refrain. Although touch is considered a boundary violation in conventional psychotherapy, psychedelic therapists sometimes offer a hand to hold or a pat on the shoulder. Consent for touch is discussed in advance and reiterated in the moment; participants and facilitators also rehearse touch beforehand. After the Hopkins and N.Y.U. sessions, participants filled out multiple questionnaires and wrote a narrative of their experience. The next day, they returned for an “integration session,” to help make sense of what can be a confusing experience. They could also participate in a follow-up psilocybin session. Of the twenty-nine participants who completed a first session, five did not return for a second.

Like virtually all the religious leaders I spoke with, Priest reported an encounter with the divine. His session began with gorgeous visuals—fractal patterns that reminded him of mosaics in a mosque. Then a spiralling current of electricity seemed to take up residence in his left thigh. He felt it move powerfully up his body and lodge in his throat. “I thought my Adam’s apple was about to explode,” he told me. Both guides could sense his distress and one reached out to comfort him. (Priest later spoke publicly about a guide touching his head, which drew criticism online, but a university review of video recordings contradicted Priest’s account.)

To Priest, the touch felt like the ritual Christian gesture of the laying on of hands. He remembers a guide holding his feet as the electrical sensation intensified. “It blew out of the top of my head, and then I started making these sounds that felt religious and spiritual and sacred,” Priest recalled. “I realized I was speaking in tongues, which I had never done before. Speaking in tongues is not an Episcopal sort of thing.”

Looking back, Priest described the experience in distinctly religious, but not strictly Christian, terms. “I would say now that my throat chakra had been blocked for a long time,” he said. “I just felt blocked in what I was preaching.” Priest described the quality of his encounter with the divine as “erotic.” So did a couple of other participants; one talked about having “a spiritual orgasm.” Priest also spoke of a reversal of gender roles. “The divine felt more masculine, and I felt like I was experiencing it the way a woman would,” he told me. “It felt so foreign to me as a man that I felt this must be how a woman experiences sexuality.” After the session, a friend came to pick Priest up and was surprised to find his face flushed. “I looked completely different,” Priest said. “I was like a new creation.”

Not everyone in the study left their session with such theological clarity. A Catholic priest from Mexico told me about hearing directly from Jesus, but a Protestant minister said with a shrug that “there was nothing particularly Christian about it.” The Buddhist roshi told me that her experience was “not life-altering” but led her “into a completely nonconceptual realm,” which she could find no words to describe. Rita Powell, now the Episcopal chaplain at Harvard, declined a second session, because her first, at N.Y.U., brought her face to face with “the abyss.” Speaking about her experience on a Harvard panel about psychedelics and religion, Powell said that her facilitators had not prepared her for something so dark. One of them “kept trying to reassure me that experiences of psilocybin were good, and beautiful, and unitive,” she said. “It seemed like kind of sloppy hippie stuff about love and harmony.” She said that, at one point in her session, she was “nowhere”: “There was neither color nor its absence. There was no form, or its absence. There was not fear. There was not joy. There was not revelation. There was nothing.” She described it as “maybe the hardest thing I had done in my life,” something that took her to “the furthest limit of human capacity.”

A peer-reviewed academic paper, “Effects of psilocybin on religious and spiritual attitudes and behaviors in clergy from various major world religions,” appears in Psychedelic Medicine this month. Its senior authors are Bossis and Stephen Ross, a psychiatry professor at N.Y.U. Swift, the funder who helped debrief some of the participants, also sent me a narrative account that highlights themes from sixteen interviews. It reads almost like a psychedelic oral history. Interviewees tended to report “authentic spiritual or religious experiences,” the account notes. A priest is quoted as saying, “I wasn’t dreaming, I wasn’t imagining, I wasn’t hallucinating.” Many participants likened their experience to those of historical and scriptural figures. “I was able to experience what the mystics were for some reason able to experience spontaneously,” a pastor said. “I don’t think that . . . my experience was less than theirs.”According to the interviews, the divine was not usually embodied or visible but, rather, felt as a presence that suffused reality, or as a sense of oneness. “I realize my very pulse is God, my very breath is God,” a rabbi said.

Several participants were surprised to encounter imagery or dogma outside their own faith. A Congregationalist minister described turning into an Aztec god and then the Hindu god Shiva. No one I spoke to, not even the rabbis, described seeing the stereotypical God of the Old Testament. And many of the religious leaders, men and women alike, experienced the divine as a feminine presence. Participants characterized God as “soothing,” “maternal,” or “womb-like.” A United Methodist pastor from Alabama called this “mind-blowing.” (Jaime Clark-Soles, the Baptist Biblical scholar in the study, told me, “God struck me as a Jewish mother at one point, which is funny, since I’m a Jesus follower.”) One of Priest’s fellow-Episcopalians, a man, reported, “I had a total deconstruction of patriarchal religion.”

It was common for participants to gain an appreciation for religions other than their own. “All the truths are in all the religions,” one rabbi said. “The active ingredients are all the same.” A Congregationalist who previously had little patience for charismatic expressions of Christianity—“the hands in the air, the talking, speaking in tongues, and all the weirdness”—observed after his session that “pathways towards the truth are even more varied than I thought.” Some felt a marked tension between the conventions of their faith and the immediacy of their psilocybin experience. “I think I have less tolerance for institutional religion now,” a Presbyterian minister is quoted as saying. “There are other ways to connect with the divine.” Here was the entire history of world religions in a nutshell: orthodoxy and authority in tension with the direct spiritual experience of the individual.

Sughra Ahmed, the only Muslim in the religious-leaders study, told me that she was petrified before her first session. Like many others, she was apprehensive about what she would learn about herself. She also feared that her participation would be considered taboo in her community of British Muslims. “Would they think I was bringing shame on us as a people?” she told me. She asked that the researchers obscure her identity in their papers, and for years she spoke to no one about her experience. But more recently she concluded that, for the sake of her personal authenticity, she needed to go on the record.

Ahmed, who is in her forties, has a round, open face and speaks in complete paragraphs. She grew up in the North of England, the daughter of immigrant Pakistanis. She went to the mosque after school every day; her parents prayed at home and fasted for Ramadan. She studied English language and literature at university and was working in I.T. when 9/11 happened. Determined to better understand both the roots of Islam and the sudden surge of prejudice—she remembered people treating her “as a security threat” when she was boarding a bus—she earned a graduate degree in Islamic studies. For a time, she wore the hijab. She was the first woman to chair the Islamic Society of Britain, and then became an associate dean for religious life at Stanford, leading prayers and preaching ecumenically at a church on campus.

Ahmed describes herself using a feminine honorific given to religious scholars or teachers: ustadha. She volunteered for the study in part because her faith wasn’t represented among the participants. “Someone had to be the Muslim seat at the table,” she told me. But, as the only Muslim, she felt that participating meant “stepping into a space not designed with you in mind.” She had also read that psychedelics had shown promise in the treatment of trauma, which the Muslim community knows something about.

Early in her first session, Ahmed told me, she felt God right behind her. “Like, if I turned around, I would bump into God,” she said. “There’s a verse in the Quran in which God says, ‘I’m closer to you than your jugular vein.’ The jugular is the life-giving source. God was with me the whole time.” For her, God was neither masculine nor feminine. “God was above gender, above everything . . . an existence, not a figure,” she said. “And God was love.” Her epiphany was a familiar psychedelic trope, but that did not make it any less profound. “It was just mind-blowingly clear how wrong we have it as human beings, and how we need to nurture love, to put it at the center of our engagement with humanity and animals and the planet,” she told me.

Ahmed said that, during her second session, “it dawned on me that the womb is the center of everything.” The memory still makes her heart beat faster, she said. “How incredibly glorious that women should have this exclusively and not anybody else! So why don’t we have a culture where we drop down at the feet of these women in awe and love and respect?” When I asked whether some Muslims would regard these ideas as heretical, she laughed. Not in her reading of Islamic scripture, which often accords women great respect—but yes, she said, in some Muslim cultures they might. “In Islam, we prostrate to God and no one else,” she said.

For years after her psilocybin sessions, Ahmed felt unmoored, as though she were struggling to regain her sense of equipoise and purpose. In her community, those who knew about psychedelics tended to lump them in with other illicit drugs. She felt that she could not talk with anybody, not even her family, about her experience, even though it was one of the most important in her life. She also felt that the team at Hopkins hadn’t done enough to help her make sense of the experience. She called the sessions “extractive”—“they were extracting data for the study”—and wished she’d had a chance to process them with people who looked like her. She found herself drifting away from prayers and rituals, and what little tolerance she’d had for misogyny and patriarchy was gone.