Ram Dass, a spritual leader and pioneer of the US psychedelic movement, has died at home in Hawaii, aged 88.
Born Richard Alpert, he worked with Timothy Leary in the 1960s on research into LSD at Harvard before travelling to India and studying spiritualism.
He was well known for his first book, Be Here Now, which sold over two million copies.
Ram Dass died peacefully at home, his foundation said, but he had suffered bouts of illness in recent years.
In 1997, he suffered a stroke that left him paralysed on the right side of his body and limited his ability to speak. In 2004, he had a life-threatening infection and cut back on travelling.
How have people reacted?
Thousands have expressed their condolences on social media.
2020 US presidential hopeful Marianne Williamson said Be Here Now had a big influence on her.
Ram Dass passed from earth a few hours ago. How perfect that he left this plane on the first night of the Festival of Lights. “Be Here Now” shifted my world when I was young, as it did for millions of others. Praise & thanks to a huge & radiant soul. May he be forever blessed.— Marianne Williamson (@marwilliamson) December 23, 2019
American producer Judd Apatow also said Ram Dass "had an enormous impact on my life".
Writer Bill Corbett said while Ram Dass was "pretty much a cliche 1960s white-guy-who-studied-in-India guru" at first, "he was never content in the superficial for long".
By his last decades, he had shed most of his guru-guy trappings and gave modest talks about serving others even when / where not comfortable, about finding grace through painful life experiences (one of which he was living through), staying present through it all.— Bill Corbett (@BillCorbett) December 23, 2019
RIP Ram Dass.
Californian Pam Mandel told the BBC she attended a lecture led by Ram Dass in college, in the mid-1980s.
Ms Mandel recalled how he talked about speaking with a dying woman who complained that death was very boring.
"And he told her, 'Okay, let's just be bored,' and she began to relax," Ms Mandel says.
"I thought about how comfortable he seemed to be, both in sitting with this woman through an experience we are so afraid of, and also, how he told this story in such a matter-of-fact way, like it was the most natural thing in the world...I had not thought of that before."
Ram Dass was born into a wealthy Jewish family in Boston, Massachusetts. His father was president of a railroad company.
Ram Dass wrote that he came from "a Jewish anxiety-ridden high-achieving tradition".
In 1952, he earned a degree in psychology at Tuft's College and his doctorate at Stanford University in 1957.
He began teaching and researching psychology at Harvard in 1958. During that time, as he would later describe, he lived in an apartment full of antiques, drove a Mercedes-Benz, owned a Cessna plane and vacationed in the Caribbean.
"I was living the way a successful bachelor professor is supposed to live in the American world of 'he who makes it'," Ram Dass wrote.
While at Harvard, Ram Dass met fellow professor Timothy Leary and the two became friends. Leary helped popularise 1960s counter-culture under the motto "turn on, tune in, drop out".
Leary was researching the effects of psilocybin, the compound responsible for the hallucinogenic properties of some mushrooms.
Leary gave Ram Dass his first taste of psilocybin at a party. Ram Dass wrote of his first experience: "The rug crawled and the pictures smiled, all of which delighted me."
The two began experimenting on the therapeutic uses of the compound, until 1963, when both were fired from Harvard - Ram Dass because he gave LSD to an undergraduate student and Leary for shirking his teaching duties.
Recreational LSD use became illegal in the US in 1968 as other studies suggested the chemical could cause dangerous psychotic reactions.
'Be Here Now'
Ram Dass began looking for alternative ways to reach enlightenment and journeyed to India, where he studied under the guru Neem Karoli Baba, also known as Maharaj-ji.
Ram Dass gave the guru a high dose of LSD, but he showed no reaction, which led Ram Dass to believe that the higher state of consciousness Maharaj-ji had achieved could not be changed by drugs.
Maharaj-ji gave Ram Dass his name - which means servant of God in Hindi - and taught him Hindu principles, meditation and yoga.
Ram Dass returned to the US in 1968, at the request of Maharaj-ji, wearing white robes, bearded and barefoot.
Some of Ram Dass' most popular quotes
- "Treat everyone you meet as if they are God in drag."
- "If you think you're enlightened, go spend a week with your family."
- "We're all just walking each other home."
- "You've gotta become somebody to become nobody."
He began lecturing across the US on spirituality, incorporating humour and principles from Hinduism, Buddhism and Sufism into his teachings.
Be Here Now, published in 1971, was his first book and became a popular guide to New Age spirituality. Apple co-founder Steve Jobs was among those who lauded the book as transformative.
But in the 1980s, Ram Dass began attempting to shed his guru image. He shaved his beard and robes but was unable to drop his recognisable Hindi name. He also disavowed some of his earlier praise of LSD.
Openly bisexual, in the 90s he said he was primarily homosexual.
In 2009, he learned he had a son, Peter Reichard, from a brief affair with a classmate during his time at Stanford.
He was a co-founder of the Seva Foundation, a nonprofit that provides eye care, including surgery and glasses, in over a dozen countries.
Ram Dass is the subject of the documentary Becoming Nobody, which was released this year.