The authors (a mycologist, chemist, and classics scholar, each respected in his field) make an informed and plausible case that the famed Mysteries conducted at Eleusis in Greece for a period of nearly two millennia in antiquity entailed psychoactive substances in a ritual context. In so doing, they find valuable lessons for the modern world in the solution of an ancient mystery. Although controversial when first published, the book's hypothesis has got much more serious attention in recent years, as scholars have increasingly come to realize the prime importance of entheogenic substances in religious rituals worldwide.All three authors have written significant books and papers relating to entheogens, and this book presents an authoritative exposition of their discoveries. This will be the first popularly accessible edition of a work that has acquired a cult reputation in the three decades since its first publication, and will attract an audience of open-minded students of earth-based spiritual practices as well as those familiar with the authors in related contexts. Its underlying theme of the universality of experiential religion, and its suppression by forces of exploitation and repression, should give it a receptive audience among many who are interested in earth religions and the reconciliation of the human and natural worlds.