AbstractThe essay offers an interpretation of psychedelic peak experiences. It criticizes the quasi-scientific naturalistic attempts to explain such experiences and offers an alternative ontology underlying a more complex sense of naturalism, thus defending an entheogenic view irreducible to mere psychological effects. First, the mainstream ontology in the paradigm of natural sciences is exposed as being a version of the ontology of presence. This fact is shown as the reason for the phenomenological gap and the impotence of the natural sciences to address human experience. Next, existential anxiety is interpreted in terms of Heidegger’s ontology and is suggested as the core dimension of possible spiritual transformation. Finally, the phenomenology of mystical psychedelic experiences (MPE) is interpreted in terms of overcoming existential anxiety– a well-documented effect of MPE – and explicated in ontological terms. The psychedelic experience is shown to be mystical in a sense of transcending the everyday mode of existential denial of the enigmatic nature of the universe by facing the nothingness in a way that transforms one’s stand within it into a stand of original belongingness to the field of emptiness (Nishitani). Different aspects of psychedelic experience are explained and co-related in terms of such a transformation.