- Terence Kemp McKenna (November 16, 1946 – April 3, 2000) was an American ethnobotanist and mystic who advocated the responsible use of naturally occurring psychedelic plants. He spoke and wrote about a variety of subjects, including psychedelic drugs, plant-based entheogens, shamanism, metaphysics, alchemy, language, philosophy, culture, technology, environmentalism, and the theoretical origins of human consciousness. He was called the “Timothy Leary of the ’90s”, “one of the leading authorities on the ontological foundations of shamanism”, and the “intellectual voice of rave culture”.