Unique in ethnography, Nurturing Doubt documents the transforming effects of field experiences on a young Mennonite who went to Argentina to work with the Toba, first as a missionary and later as an anthropologist. Elmer Miller insightfully probes the documents--diaries, field journals, and letters--of both his lives, revealing as he does the ways in which his perceptions of the Toba--and theirs of him--changed when his role changed. Deeply affected by an upbringing in which he had been taught that doubting was "sinful," Miller gradually found that he doubted not only the validity of the missionary mandate but also his ethnographic mandate and the whole practice of anthropology. His exploration of how his doubt was transformed from a negative activity into a positive philosophical attitude underscores the richness of his relationships with the Toba. In depicting the move from theological to anthropological discourse, Miller contributes to current debates over the form and purpose of ethnographic investigation and reporting.