In the current discourses and practices of indigenous people of Amazonia, there is a mixture of various, conflicting kinds of rationality, which points out the coexistence of different conceptual frameworks. This coexistence appears in so many diverse forms that it would be very simplifying to describe it merely in terms of acculturation and resistance. It can be better approached as a cultural heterogeneity, which has to be analyzed case by case. This article focuses on an Ashéninka woman, who was one of my main informants ten years ago in a project for the evaluation and analysis of ethnobotanical knowledge on the Brazil-Peru border, and who later on was responsible for taking care of a medicinal garden for a project financed by a European NGO. This led to a marked impoverishment of her ethnomedicinal knowledge. To explain such a paradoxical outcome, the paper describes former and current processes of regional and interethnic borrowing, analyzes the indigenous conceptions about knowledge and therapeutic efficacy, and underlines the emphasis on relational criteria. These criteria are precisely what this woman is giving up now.