The ’Introduction’ lays the intellectual foundation for the book by situating mind-altering substances within the broader arc of human cultural, neurological, and technological evolution. It argues that altered states of consciousness — whether chemically, behaviourally, or digitally induced — are not peripheral but central to the human experience. The chapter outlines how the search for transcendence, novelty, and meaning has driven innovations in medicine, ritual, and technology across millennia. It introduces the concept of ’experiential adaptation’ to describe how societies continually modify consciousness in response to environmental, social, and symbolic pressures. The introduction also maps out the interdisciplinary methodology of the book, drawing from anthropology, neuroscience, history, digital media studies, and future forecasting. It prepares the reader to navigate a narrative that stretches from Palaeolithic natural and artificial, healthy and pathological, sacred and simulated.