The institutionalized roles of psychedelics within the religions of cultures around the world indicate these substances were central to the evolution of spiritual experiences and religious institutions (See Rush, 2013; Ellens, 2014; Winkelman, 2019; Winkelman, 2014). Shamanism was central to that development. Psychedelics elevate this ancient mode of thought, one which has been long recognized in the philosophical and contemplative traditions, an intuitive mode of cognition rich in significance and meaning that is conveyed through visions and imagistic symbols. These features of knowing are liberated by psychedelics through interference with our normal top-down cognitive dynamics, compromising the dominance of higher cognitive functions and consequently releasing processes and information from ancient brain structures. The shamanic use of psychedelics included a wide range of psychoactive agents with variable chemistry and divergent applications, a recognition of the selective effects of these diverse substances, and their potential applications in the treatment of a wide range of conditions. These treatment strategies and "best uses" a includes a recognition of the importance of set and setting, embodied in the ritual structures developed for their use; the principles for preparation of healers and patients for their ingestion for producing optimal effects; preparations involving restrictions on diet and sexual abstinence; a group ritual context involving chanting and singing; incorporation of the ritual into overnight activities that integrate them with dream processes; and the cosmological perspectives on these substances and their nature that provide conceptual frameworks for managing the experiences.