Who coined the phrase "turn on, tune in, drop out"?

The phrase "turn on, tune in, drop out" was coined by Timothy Leary, an American psychologist and advocate for psychedelic drugs. He popularized this expression in the 1960s, emphasizing a movement towards heightened consciousness through the use of psychedelics. The phrase encapsulates a philosophy of engaging with one's inner self and the broader cultural revolution of that era, encouraging individuals to explore altered states of consciousness and reject mainstream societal norms. Timothy Leary's work and his charismatic personality contributed significantly to the countercultural movements of the 1960s, making this phrase synonymous with the spirit of those times.

While other figures, such as Mario Savio, Jimi Hendrix, and Abbie Hoffman, played pivotal roles in the counterculture and anti-establishment movements, they did not coin this particular phrase, making Leary the correct attribution for this well-known slogan.