“Turn on, tune in, drop out” is a counterculture phrase coined by Timothy Leary in the 1960s.

The phrase came to him in the shower one day after Marshall McLuhan suggested to Leary that he come up with “something snappy” to promote the benefits of LSD. It is an excerpt from a prepared speech he delivered at the opening of a press conference in New York City on September 19, 1966. This phrase urged people to initiate cultural changes through the use of psychedelics and by detaching themselves from the existing conventions and hierarchies in society. The phrase was derided by more conservative critics.

The phrase is derived from this part of Leary’s speech: “Like every great religion of the past we seek to find the divinity within and to express this revelation in a life of glorification and the worship of God. These ancient goals we define in the metaphor of the present — turn on, tune in, drop out.”

Leary later explained in his 1983 autobiography Flashbacks:

“‘Turn on’ meant go within to activate your neural and genetic equipment. Become sensitive to the many and various levels of consciousness and the specific triggers that engage them. Drugs were one way to accomplish this end. ‘Tune in’ meant interact harmoniously with the world around you – externalize, materialize, express your new internal perspectives. Drop out suggested an elective, selective, graceful process of detachment from involuntary or unconscious commitments. ‘Drop Out’ meant self-reliance, a discovery of one’s singularity, a commitment to mobility, choice, and change. Unhappily my explanations of this sequence of personal development were often misinterpreted to mean ‘Get stoned and abandon all constructive activity.

Source: Wikipedia