Timothy Francis Leary (October 22, 1920 – May 31, 1996) was an American Psychologist and Writer known for advocating the exploration of the therapeutic potential of psychedelic drugs under controlled conditions. Leary conducted experiments under the Harvard Psilocybin Project when LSD and psilocybin were still legal in the United States, resulting in the Concord Prison Experiment and the Marsh Chapel Experiment. The scientific legitimacy and ethics of his research were questioned by other Harvard faculty because he took psychedelics together with research subjects and pressured students in his class to take psychedelics in the research studies. Leary's colleague, Richard Alpert (Ram Dass), was fired from Harvard University on May 27, 1963 for giving psilocybin to an undergraduate student outside of their research study despite the university only allowing graduate students to receive psilocybin as research subjects. Leary was planning to leave Harvard when his teaching contract expired in June, the following month. He was fired, for "failure to keep classroom appointments", with his pay docked on April 30. National illumination as to the effects of psychedelics did not occur until after the Harvard scandal.

He attended the College of the Holy Cross in Worcester, Massachusetts from September 1938 to June 1940. Under pressure from his father, he then accepted an appointment as a cadet in the United States Military Academy at West Point, New York. In the first months as a "plebe", he was given numerous demerits for rule infractions and then got into serious trouble for failing to report infractions by other cadets when on supervisory duty. He was alleged to have gone on a drinking binge and to have failed to "come clean" about it. He was asked by the Honor Committee to resign for violating the Academy's honor code. He refused and was "silenced"—that is, shunned and ignored by his fellow cadets as a tactic to pressure him to resign. He was acquitted by a court-martial, but the silencing measures continued in full force, as well as the onslaught of demerits for small rule infractions. The treatment continued in his sophomore year, and his mother appealed to a family friend, United States Senator David I. Walsh, head of the Senate Naval Affairs Committee, who conducted a personal investigation. Behind the scenes, the Honor Committee revised its position and announced that it would abide by the court-martial verdict. Leary then resigned and was honorably discharged by the Army. Almost 50 years later, he said that it was "the only fair trial I've had in a court of law".

To the chagrin of his family, Leary elected to transfer to the University of Alabama in late 1941 because of the institution's expeditious response to his application. He enrolled in the university's ROTC program, maintained top grades, and began to cultivate academic interests in psychology (under the aegis of the Middlebury and Harvard-educated Donald Ramsdell) and biology, but he was expelled a year later for spending a night in the female dormitory, losing his student deferment in the midst of World War II.

Leary was drafted into the United States Army and reported for basic training at Fort Eustis in January 1943. He remained in the non-commissioned track while enrolled in the psychology subsection of the Army Specialized Training Program, including three months of study at Georgetown University and six months at Ohio State University.

After retroactive suspension and eventual reinstatement at the University of Alabama, he ultimately completed his degree via correspondence courses together with psychology credits for his work at Ohio State and graduated on 23 August 1945. Following the resolution of the war, Leary decided to pursue an academic career. In 1946 he received an M.S. degree in psychology at Washington State University, where he studied under noted educational Psychologist Lee Cronbach. His M.S. thesis was a study of the clinical applications of the Wechsler Adult Intelligence Scale.

In 1947, Marianne gave birth to their first child, Susan. A son, Jack, was born two years later. In 1950, Leary received a Ph.D. degree in clinical psychology from the University of California, Berkeley. Like many social Scientists of the postwar epoch, Leary was galvanized by the objectivity of modern physics; his doctoral dissertation (The Social Dimensions of Personality: Group Structure and Process) approached group therapy as a "psychlotron" from which behavioral characteristics could be derived and quantified in a manner analogous to the periodic table, presaging his later development of the interpersonal circumplex.

He was also an early influence on Transactional Analysis. His concept of the four Life Scripts, dating back to 1951, became an influence on TA by the late 1960s, popularised by Thomas Harris in his book, I'm OK, You're OK.

The new Ph.D. stayed on in the Bay Area as an assistant clinical professor of medical psychology at the University of California, San Francisco; concurrently, Leary co-founded Kaiser Hospital's psychology department in Oakland, California and maintained a private consultancy. In 1952, the Leary family spent a year in Spain, subsisting on a research grant. According to Berkeley colleague Marv Freedman, "Something had been stirred in him in terms of breaking out of being another cog in society..."

From 1954 or 1955 to 1958, Leary was Director of psychiatric research at the Kaiser Family Foundation. In 1957, Leary's The Interpersonal Diagnosis of Personality was published and was hailed as the 'most important book on psychotherapy of the year' by the Annual Review of Psychology.

Despite his nascent professional success, his marriage was strained by multiple infidelities and mutual alcohol abuse. Marianne eventually committed suicide in 1955, leaving him to raise their son and daughter alone. He described himself during this period as "an anonymous institutional employee who drove to work each morning in a long line of commuter cars and drove home each night and drank martinis ... like several million middle-class, liberal, intellectual robots."

On May 13, 1957, Life magazine published an article by R. Gordon Wasson that documented the use of psilocybin mushrooms in religious rites of the indigenous Mazatec people of Mexico. Anthony Russo, a colleague of Leary's, had experimented with psychedelic (or entheogenic) Psilocybe mexicana mushrooms on a trip to Mexico and told Leary about it. In August 1960, Leary traveled to Cuernavaca, Mexico with Russo and consumed psilocybin mushrooms for the first time, an experience that drastically altered the course of his life. In 1965, Leary commented that he had "learned more about ... (his) brain and its possibilities ... [and] more about psychology in the five hours after taking these mushrooms than ... in the preceding 15 years of studying and doing research in psychology."

Following the termination of his commodious National Institute of Mental Health research grant (precipitated by his absence from a meeting with a NIMH investigator), Leary and his children relocated to Europe in 1958, where he attempted to write his next book on psychology while subsisting on small grants and insurance policies. He was overcome by indigence during an unproductive stay in Florence, and returned to academia in late 1959 as a lecturer in clinical psychology at Harvard University at the behest of Frank Barron (a colleague from Berkeley) and David McClelland. During this period, he resided with his children in nearby Newton, Massachusetts. In addition to his teaching duties, Leary was affiliated with the Harvard Center for Research in Personality under McClelland and oversaw the Harvard Psilocybin Project and concomitant experiments in conjunction with assistant professor Richard Alpert. In 1963, Leary was terminated for failing to give his scheduled class lectures, while he claimed that he had fulfilled his teaching obligations in full. The decision to dismiss him may have been influenced by his role in the popularity of psychedelic substances among Harvard students and faculty members, which were legal at the time.

World religion scholar Huston Smith was "turned on" by Leary after being introduced to him by Aldous Huxley in the early 1960s. The experience was interpreted as a deeply religious one by Smith, and is described in detailed religious terms in Smith's later work Cleansing of the Doors of Perception. Smith asked Leary, to paraphrase, whether he knew the power and danger of what he was conducting research with. In Mother Jones Magazine, 1997, Smith commented:

Timothy Leary was an early influence on Game Theory applied to psychology having introduced the concept to the International Association of Applied Psychology in 1961, at their annual conference in Copenhagen.

Leary and Alpert founded the International Federation for Internal Freedom (IFIF) in 1962 in Cambridge, Massachusetts, in order to carry out studies in the religious use of psychedelic drugs. This was run by Lisa Bieberman (now known as Licia Kuenning), a friend of Leary. The Harvard Crimson described her as a "disciple" who ran a Psychedelic Information Center out of her home and published a national LSD newspaper. That publication was actually Leary and Alpert's journal Psychedelic Review, and Bieberman (a graduate of the Radcliffe Institute for Advanced Study at Harvard, who had volunteered for Leary as a student) was its circulation manager. Leary and Alpert's research attracted so much public attention that many who wanted to participate in the experiments had to be turned away due to the high demand. To satisfy the curiosity of those who were turned away, a black market for psychedelics sprang up near the Harvard campus.

Leary's activities interested siblings Peggy, Billy, and Tommy Hitchcock, heirs to the Mellon fortune, who helped Leary and his associates acquire a rambling 64-room mansion in 1963 on an estate in Millbrook, New York, where they continued their experiments. Peggy Hitchcock was Director of the International Federation for Internal Freedom (IFIF)'s New York branch, and her brother Billy rented the estate to IFIF. Leary and Alpert immediately set up a communal group with former Psilocybin Project members at the Hitchcock Estate (commonly known as "Millbrook"), and the IFIF was subsequently disbanded and renamed the Castalia Foundation (after the intellectual colony in Herman Hesse's The Glass Bead Game). The group's journal was the Psychedelic Review. The core group at Millbrook sought to cultivate the divinity within each person, and often participated in group LSD sessions facilitated by Leary. The Castalia Foundation hosted weekend retreats on the estate where people paid to undergo the psychedelic experience without drugs, through meditation, yoga, and group therapy sessions. Leary later wrote:

Leary married model Birgitte Caroline "Nena" von Schlebrügge in 1964 at Millbrook. Both Nena and her brother Bjorn, known as the "Baron," were friends of the Hitchcocks. D. A. Pennebaker, also a Hitchcock friend, and Cinematographer Nicholas Proferes documented the event in the short film You're Nobody Till Somebody Loves You. Charles Mingus played piano. The marriage lasted a year before von Schlebrügge divorced Leary in 1965 — she married Indo-Tibetan Buddhist scholar and ex-monk Robert Thurman in 1967 and gave birth to Ganden Thurman that same year. Actress Uma Thurman, her second child, was born in 1970.

Leary's first run-in with the law came on December 20, 1965, when Leary was arrested for possession of marijuana. Leary decided to take his two children, Jack and Susan, and his girlfriend Rosemary Woodruff to Mexico for an extended stay to write a book. On their return from Mexico to the United States, a US Customs Service official found marijuana in Susan's underwear. They had crossed into Nuevo Laredo, Mexico in the late afternoon and discovered that they would have to wait until morning for the appropriate visa for an extended stay. They decided to cross back into Texas to spend the night, and were on the US-Mexico bridge when Rosemary remembered that she had a small amount of marijuana in her possession. It was impossible to throw it out on the bridge, so Susan put it in her underwear. After taking responsibility for the controlled substance, Leary was convicted of possession under the Marihuana Tax Act of 1937 on March 11, 1966, sentenced to 30 years in prison, fined $30,000, and ordered to undergo psychiatric treatment. He appealed the case on the basis that the Marihuana Tax Act was unconstitutional, as it required a degree of self-incrimination in blatant violation of the Fifth Amendment.

Repeated FBI raids ended the Millbrook era. Leary told author and Prankster Paul Krassner regarding a 1966 raid by Liddy, "He was a government agent entering our bedroom at midnight. We had every right to shoot him. But I've never owned a weapon in my life. I have never had and never will have a gun around."

At the end of 1967, Leary moved to Laguna Beach, California and made many new friends in Hollywood. "When he married his third wife, Rosemary Woodruff, in 1967, the event was directed by Ted Markland of Bonanza. All the guests were on acid."

On December 26, 1968, Leary was arrested again in Laguna Beach, California, this time for the possession of two marijuana "roaches". Leary alleged that they were planted by the arresting officer, but was convicted of the crime. On May 19, 1969, The Supreme Court concurred with Leary in Leary v. United States, declared the Marihuana Tax Act unconstitutional, and overturned his 1965 conviction.

On that same day, Leary announced his candidacy for Governor of California against the Republican incumbent, Ronald Reagan. His campaign slogan was "Come together, join the party." On June 1, 1969, Leary joined John Lennon and Yoko Ono at their Montreal Bed-In, and Lennon subsequently wrote Leary a campaign song called "Come Together".

On January 21, 1970, Leary received a 10-year sentence for his 1968 offense, with a further 10 added later while in custody for a prior arrest in 1965, for a total of 20 years to be served consecutively. On his arrival in prison, he was given psychological tests used to assign inmates to appropriate work details. Having designed some of these tests himself (including the "Leary Interpersonal Behavior Inventory"), Leary answered them in such a way that he seemed to be a very conforming, conventional person with a great interest in forestry and gardening. As a result, he was assigned to work as a gardener in a lower-security prison from which he escaped in September 1970, saying that his non-violent escape was a humorous prank and leaving a challenging note for the authorities to find after he was gone.

In 1971, the couple fled to Switzerland, where they were sheltered and effectively imprisoned by a high-living arms dealer, Michel Hauchard, who claimed he had an "obligation as a gentleman to protect philosophers"; Hauchard intended to broker a surreptitious film deal, and forced Leary to assign his Future earnings (which Leary eventually won back). In 1972, President Richard Nixon's attorney general, John Mitchell, persuaded the Swiss government to imprison Leary, which it did for a month, but refused to extradite him to the United States.

Leary feigned cooperation with the FBI's investigation of the Weathermen and its radical attorneys by giving them information that they already had or which he saw as being of little consequence; in response, the FBI gave him the code name "Charlie Thrush". In a 1974 news conference, Allen Ginsberg, Ram Dass, and Leary's 25-year-old son Jack denounced Leary, calling Leary a "cop informant," a "liar," and a "paranoid schizophrenic." Leary would later claim, and members of the Weathermen would later support his claim, that no one was ever prosecuted based on any information he gave to the FBI. In 1999 a letter was written by 22 'Friends of Timothy Leary' in an attempt to defend his reputation in light of the publication of FBI files relating to the same case. It was signed by authors such as Douglas Rushkoff, Ken Kesey, and Robert Anton Wilson. Susan Sarandon and Leary's goddaughter Wynona Ryder also signed the letter.

Leary's colonization plan varied greatly through the years. According to his initial plan to leave the planet, 5,000 of Earth's most virile and intelligent individuals would be launched on a vessel (Starseed 1) equipped with luxurious amenities. This idea was inspired by the plotline of Paul Kantner's concept album Blows Against The Empire, which in turn was derived from Robert A. Heinlein's Lazarus Long series. Whilst in Folsom Prison in the winter of 1975-76 Leary had become enamoured by Gerard O'Neill's egalitarian plans to construct giant Eden-like High Orbital Mini-Earths (documented in the Robert Anton Wilson lecture H.O.M.E.s on LaGrange) using existing Technology and raw materials from the Moon, orbital rock and obsolete satellites.

Leary was released from prison on April 21, 1976 by Governor Jerry Brown. After briefly relocating to San Diego, he took up residence in Laurel Canyon and continued to write books and appear as a lecturer and (by his own terminology) "stand-up philosopher". In 1978 he married filmmaker Barbara Blum, also known as Barbara Chase, sister of Actress Tanya Roberts. Leary adopted Blum's son Zachary and raised him as his own. During this period, Leary took on several godchildren, including Actress Winona Ryder (the daughter of his archivist, Michael Horowitz) and current MIT Media Lab Director Joi Ito.

His ideas influenced the work of his friend Robert Anton Wilson. This influence went both ways, and Leary admittedly took just as much from Wilson. Wilson's book Prometheus Rising was an in-depth, highly detailed and inclusive work documenting Leary's eight-circuit model of consciousness. Although the theory originated in discussions between Leary and a Hindu holy man at Millbrook, Wilson was one of the most ardent proponents of it and introduced the theory to a mainstream audience in 1977's bestselling Cosmic Trigger. In 1989, they appeared together on stage in a dialog entitled The Inner Frontier hosted by the Association for Consciousness Exploration, (the same group that had hosted Leary's first Cleveland appearance in 1979).

In the 1980s, Leary became fascinated by computers, the Internet, and virtual reality. Leary proclaimed that "the PC is the LSD of the 1990s" and admonished bohemians to "turn on, boot up, jack in". He became a promoter of virtual reality systems, and sometimes demonstrated a prototype of the Mattel Power Glove as part of his lectures (as in From Psychedelics to Cybernetics). Around this time he befriended a number of notable people in the field such as Jaron Lanier and Brenda Laurel, a pioneering researcher in virtual environments and human–computer interaction. With the rise of cyberdelic counter-culture, he served as consultant to Billy Idol in the production of the latter's 1993 album Cyberpunk.

Leary began to foster an improbable friendship with former foe G. Gordon Liddy, the Watergate burglar and conservative radio talk-show host. They toured the lecture circuit in 1982 as ex-cons (Liddy having been imprisoned after high-level involvement in the Watergate scandal) debating different social and fiscal issues from gay rights and abortion to welfare and the environment, with Leary generally espousing left-wing views and Liddy continuing to conform to a right-wing stance. The tour generated massive publicity and considerable funds for both. The personal appearances, a successful documentary called Return Engagement chronicling the tour, and the concurrent release of the autobiography Flashbacks helped to return Leary to the spotlight. In 1988, Leary held a fundraiser for Libertarian presidential candidate Ron Paul.

Leary was reportedly excited for a number of years by the possibility of freezing his body in cryonic suspension, and he publicly announced in September 1988 that he had signed up with Alcor for such treatment after having appeared at Alcor's grand opening the year before. He did not believe he would be resurrected in the Future, but did believe that cryonics had important possibilities even though he thought it had only "one chance in a thousand". He called it his "duty as a futurist", and helped publicize the process and hoped it would work for his children and grandchildren if not for him, although he said he was "lighthearted" about it. He was connected with two cryonic organizations, first Alcor and then CryoCare, one of which delivered a cryonic tank to his house in the months before his death. Leary initially announced he would freeze his entire body, but due to lack of funds decided to freeze his head only. He then changed his mind again, and requested that his body be cremated, with his ashes scattered in space.

In 1990, his daughter Susan, aged 42, was arrested in Los Angeles for firing a bullet into her boyfriend's head as he slept. Twice she was ruled mentally unfit to stand trial. While in jail, after years of mental instability, she committed suicide by tying a shoelace around her neck and hanging herself. After his separation and subsequent divorce from Barbara in 1992, he ensconced himself in a circle of artists and cultural figures encompassing figures as diverse as actors Johnny Depp, Susan Sarandon, and Dan Aykroyd; Zach Leary; his grandson Ashley Martino and his granddaughters Dieadra Martino and Sara Brown; author Douglas Rushkoff; publisher Bob Guccione, Jr.; and goddaughters Ryder and artist/music–photographer Hilary Hulteen. Despite declining health, he maintained a regular schedule of public appearances through 1994. In the same year he was honored at a symposium of the American Psychological Association.

Leary's last book before he died was Chaos and Cyber Culture, published in 1994. In it he wrote, "The time has come to talk cheerfully and joke sassily about personal responsibility for managing the dying process." His book Design for Dying which tried to give a new perspective on death and dying, was published posthumously. Leary wrote about his belief that death is "a merging with the entire life process."

In January 1995, Leary was diagnosed with inoperable prostate cancer. He then notified Ram Dass and other old friends, and began the process of directed dying, which he termed "designer dying." Leary did not reveal the condition to the press at that time, but did so after the death of Jerry Garcia in August. Leary and Ram Dass reunited before Leary's death in May 1996, as seen in the documentary film Dying to Know: Ram Dass & Timothy Leary.

The film Timothy Leary's Dead (1996) contains a simulated sequence in which he allows his bodily functions to be suspended for the purposes of cryonic preservation. His head is removed, and placed on ice. The film ends with a sequence showing the creation of the artificial head used in the film.

Seven grams of Leary's ashes were arranged by his friend at Celestis to be buried in space aboard a rocket carrying the remains of 23 others, including Gene Roddenberry (creator of Star Trek), Gerard O'Neill (space physicist), and Krafft Ehricke (rocket scientist). A Pegasus rocket containing their remains was launched on April 21, 1997 and remained in orbit for six years until it burned up in the atmosphere.

The movie Fear and Loathing in Las Vegas (1998), adapted from a 1971 novel of Hunter S. Thompson, portrays heavy psychedelic drug use and mentions Leary when the protagonist ponders the meaning of the acid wave of the sixties:

At a stopover in the UK, as Leary was being flown back to the US in custody, he requested political asylum from Her Majesty's government to no avail. Back in America, he was held on $5 million bail ($21.5 million in 2006) since Nixon had earlier labeled him as "the most dangerous man in America." At that time, it was the largest bail on a private citizen in American history. The judge at his remand hearing stated, "If he is allowed to travel freely, he will speak publicly and spread his ideas," Facing a total of 95 years in prison, Leary hired Criminal defense attorney Bruce Margolin. Leary mostly directed his own defense strategy, which proved to be unsuccessful, as the jury convicted him after deliberating for less than two hours. The Brotherhood drug conspiracy charges were dropped for lack of evidence, but Leary received five years for his prison escape added to his original 10-year sentence. In 1973, he was sent to Folsom Prison in California, and put in solitary confinement. While in Folsom, he was placed in a cell right next to Charles Manson, and though they could not see each other, they could talk together. In their discussions, Manson was surprised and found it difficult to understand why Leary had given people LSD without trying to control them. At one point, Manson said to Leary, "They took you off the streets so that I could continue with your work."

In June 2011, The New York Times reported that the New York Public Library had acquired Leary's personal archives, including papers, videotapes, photographs and other archival material from the Leary estate, including correspondence and documents relating to Allen Ginsberg, Aldous Huxley, william Burroughs, Jack Kerouac, Ken Kesey, Arthur Koestler, G. Gordon Liddy and other prominent cultural figures. The collection became available in September 2013.

Leary argued that psychedelic substances—in proper doses, in a stable setting, and under the guidance of psychologists—could alter behavior in beneficial ways not easily attainable through regular therapy. His research focused on treating alcoholism and reforming Criminals. Many of his research subjects told of profound mystical and spiritual experiences which they said permanently and positively altered their lives.

Leary's ashes were also given to close friends and family. In 2015, Susan Sarandon brought some of his ashes to the Burning Man festival in Black Rock City, Nevada, and put them into an art installation there. The ashes were burned, along with the installation, on September 6, 2015.