This book opens with a description of my first entheogen experience, and - because objective understanding of these substances is the book's primaryaim - this leaves me with no alternative but to talk about myself; for there is no direct line from chemical brain states to the experiences they occasion. Invariably the psychological makeup of the subject (his “set,” as investigingestion, its “setting.” The reader needs to be aware of this, for whether Iators call it) acts as a filter, as do the circumstances surrounding the ingestion, its “setting.” The reader needs to be aware of this, for whether I am reporting experiences I have had or registering conclusions that I have reached on the tricky issues this book takes up, I (the book's author) am inevitably present in its pages for establishing the angle from which the subject is viewed. The object of this Introduction is to make that angle clear, and it can be relatively brief, for only things that bear on the book's subject need be included.