The project of ontological anthropology expounded by Philippe Descola has unexplored merits for a critical and secular anthropology of Christian conversion in indigenous societies. Drawing on Shuar descriptions of their healing practice in a context of medical pluralism in southeast Ecuador, this article argues that for animist peoples, Protestant Evangelicalism constitutes a step toward philosophical materialism or ‘naturalism’. While Shuar healing reserves a central place for hallucinogenic plant-induced visions for personal empowerment and shamanic healing, Shuar Evangelicals express a preference for engaging only the material qualities of medicinal plants. This is not, however, the consequence of adopting a disenchanted material cosmology but of a submissive mode of relating to the immaterial aspects of reality normally engaged in ancestral Shuar ontology. The article thereby extends the ontological turn’s emphasis on what is known to a consideration of modes of relation to ontological content.