Who is responsible for this phrase: "Turn on, tune in, drop out."

This iconic three-part slogan became the unofficial motto of the 1960s counterculture, and its source was Timothy Leary, a former Harvard psychologist turned psychedelic advocate. He first introduced the phrase to a crowd of thousands at the Human Be-In festival in San Francisco's Golden Gate Park in January 1967. The event was a pivotal moment for the hippie movement, and Leary's catchy, directive phrase provided a powerful mantra for a generation questioning authority and tradition.

Leary later explained that the phrase had a specific, multi-layered meaning. "Turn on" meant to go within and activate your own consciousness, often with the aid of psychedelics like LSD, to unlock new levels of awareness. "Tune in" meant to interact harmoniously with the world around you once you were awakened, to become sensitive to your environment and redirect your life based on this new perspective.

Finally, "drop out" was perhaps the most misunderstood part. It did not simply mean to quit school or a job in an act of lazy rebellion. For Leary, it suggested a process of graceful and selective detachment from the involuntary commitments and social programming of mainstream society. It was a call for self-reliance, individuality, and the conscious choice to build a new way of living, rather than blindly following the old one.