Juan Mendez Nieto was a XVI century physician of Portuguese Jewish ancestry who studied in the University of Salamanca and arrived in 1569 in the city of Cartagena possibly running from the Inquisition after living for a time in Santo Domingo. His social condition as a New Christian made him a target for the secular and clerical institutions of the colonies. Once in Tierra Firme (today the northern Colombian and suramerican coast) he began a very intense medical activity, one in which we could find a kaleidoscope of the problematic Spanish modernity and knowledge from other sources of his everyday contact with the Indian and African medicinal lore. His only surviving book: Discursos Medicinales (Medicine Discourses) finished sometime around 1608 or a year before has the merit of being the first such text written entirely in America. In this work one can identify the ethnographic venue of the author and an affinity for highlighting the socio cultural context of medical symptoms and the practical know how of the clinical physician. His practice can be interpreted by the tension caused by a baroque ethos that in the midst of the new world shares thought styles of that preceded modernity and that faced collectives of local thought dominated by the imagery and coercive power of the Inquisition. In this essay we will try to hermeneutically read the life and work of Mendez Nieto by means of the notions of thought-styles and thoughtcollectives originally proposed by the physician and sociologist of science Ludwick Fleck.