I was very much interested, ever since my undergraduate years here at Harvard, when I wrote a paper on the peyote plant. That is a hallucinogen, a cactus of the Southwest and of Mexico. That interest carried through all my work. Among primitive peoples, I think in most parts of the world, certainly in the Amazon, there is no concept of organically caused sickness and death. It is all done by the invisible arrows from malevolent spirits. And, the hallucinogens are used in magical religious rites by primitive peoples. They’re not abused as they are in our country and Europe by “civilized” people who have adopted them and use them without that religious background. The medicine man, and sometimes the ordinary Indians, through these visions that most of them produce, think that they are able to confer with the ancestors, or with the malevolent spirits. And, the medicine man thinks he can diagnose diseases which are caused by these malevolent spirits and somehow — either with plants, or with mumbo-jumbo, or both, or with certain rituals and dances — affect cures.