Dennis Jon McKenna (born December 17, 1950 in Paonia, Colorado) is an American ethnopharmacologist, research pharmacognosist, lecturer and author. He is the brother of well-known psychedelics proponent Terence McKenna and is a founding board member and the director of ethnopharmacology at the Heffter Research Institute, a non-profit organization concerned with the investigation of the potential therapeutic uses of psychedelic medicines.
Quotes
Terence's pivotal, existential crisis came abruptly, some time in '88 or '89. Everything that happened after that event was fallout. I don't know exactly when it happened, and I don't know exactly what happened; I am piecing it together from what Kat has told me, and she has volunteered few details, and I am reluctant to probe.
It happened when they were living for a time on the big island, and it was a mushroom trip they shared that was absolutely terrifying for Terence. It was terrifying because, for some reason, the mushroom turned on him. The gentle, wise, humorous mushroom spirit that he had come to know and trust as an ally and teacher ripped back the facade to reveal an abyss of utter existential despair. Terence kept saying, so Kat told me, that it was "a lack of all meaning, a lack of all meaning." And this induced panic in Terence, and probably, I speculate, a feeling he was going mad. He couldn't deal with it. Kat's efforts to reassure him were fruitless. After that experience, he never again took mushrooms, and he took other psychedelics, such as DMT and ayahuasca, only on rare occasions and with great reluctance.
Whatever the specific content of the psychedelic experience might have been that triggered the cognitive collapse of Terence's worldview and precipitated his existential crisis, what was most remarkable was that he did not see it coming.