What is Terence Mckenna?

Terence Kemp McKenna (November 16, 1946 – April 3, 2000) was an Irish-American philosopher, psychonaut, researcher, spiritual teacher, speaker and writer on many subjects; such as human consciousness, psychedelic drugs, the evolution of civilizations, the origin and the end of the universe, cybernetics, alchemy, and extraterrestrial beings.