The description of Patagonia and the contiguous parts of South America was written by the English Missioner Jesua Thomas Falkner and published in 1774. It was part of the enormous textual output made by the Jesuit parents after the company had been expelled and dissolved; these works concerned the geographical, natural and social area in which they had measured. The article will look at the different discursive forms of jesuit writing to try to establish in which rhetoric model Thomas Falkner’s work can best be registered. A true distinctive sign with the work of the English jesuit is that it complied with very few textual and formal requirements of the illustrated movement. This discrepancy towards Illustration is rather paradoxical because it was the only jesuita who had the necessary academic training to develop a text that met all these requirements.