In this study I argue that psychedelic substances served as a doorway through which spirituality entered the scientific laboratory to an unprecedented degree given their traditionally demarcated relationship by making spirituality more amenable to scientific paradigms and accessible to scientific methodologies. I conduct a feminist discourse analysis of the politics of knowledge enacted in this unique intersection of spirituality and science in the psychedelic sciences. I draw on feminist theories of science and knowledge which conceptualize science as a dominant knowledge constituted through and productive of the intersecting and historically hierarchical systems of power of race, class, gender and nation. Using discourse analysis techniques, I analyze a documentary archive I created through a theoretically driven sampling of the psychedelic sciences of spirituality from the 1930's to the present. In Chapter 2, I analyze how spirituality was brought forward and negotiated in these sciences. I argue that psychedelic scientists utilized a range of what I call tactics of legitimation to justify the scientific study of these peculiar substances and the spirituality with which they are associated vis-à-vis dominant scientific knowledges and I analyze the attendant epistemological costs of this assimilation. In Chapter 3, I analyze the efforts to integrate psychedelic substances and the spiritual experiences they induce into western therapeutic assumptions and practices. I argue that their efforts to scientifically determine the mysticality of mystical experiences and their pursuits of scientific liturgical authority over the administration of psychedelic sacraments resulted in the emergence of a would-be psychiatric clerical authority. In Chapter 4, I analyze the efforts to integrate and develop indigenous spiritual psychedelic knowledges and practices across each step of a bioprospecting model from plant identification to the determination of mechanisms of action and finally to drug development studies. I argue that in each step indigenous spiritual knowledges were assimilated into dominant scientific assumptions and practices reifying western scientific authority over indigenous knowledges and practices and reinforcing historically hierarchical colonial relationships despite the `good intentions' of these psychedelic scientists. In the final chapter of this study I discuss future sociological and feminist projects analyzing these peculiar psychedelic sciences and spiritual substances.