'Naturalism' is invoked with increasing frequency by anthropologists as a distinctively Western ontology which posits a shared unitary nature, upon which are overlain multiple 'cultures', 'perspectives', or 'worldviews'. But where, if at all, is this ontology to be found? Anthropologists working outside Europe and America have in various ways been urging colleagues to challenge 'our' naturalism in order to be able to take seriously alternative ethnographic realities. In the meantime, anthropologists and STS scholars who study European or American settings ethnographically have increasingly been arguing that 'we' were never (quite) naturalist to begin with. This double move shores 'naturalism' up as a conceptual object, but renders it ethnographically elusive, a perpetually receding horizon invoked in accounts of something else. This introduction explores this paradox and presents the subsequent articles' various experiments with what might seem an impossible task: the ethnography of naturalism itself.