Terence Kemp McKenna was an American ethnobotanist, lecturer, and author who advocated for the responsible use of naturally occurring psychedelic plants and mushrooms. He spoke and wrote about a variety of subjects, including psychedelic drugs, plant-based entheogens, shamanism, metaphysics, alchemy, language, philosophy, culture, technology, ethnomycology, 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". Critical reception of McKenna's work was deeply polarized, with critics accusing him of promoting dangerous ideas and questioning his sanity, while others praised his writing as groundbreaking, humorous, and intellectually provocative.