The logic of medical discovery: the case of Jenner’s inquiry on variolae vaccinae

Jenner (1749–1826) is known as the father of the smallpox vaccine. Through an inferential analysis of Jenner’s report of inquiry, in which medical practice and medical research are intrinsically intertwined, we highlight his use of abductive hypotheses. Our understanding of abduction is based on the Gabbay and Woods (2005, The Reach of Abduction Insight and Trial, 2, 39) model, in which hypotheses can be activated even when they have not been confirmed, as well as Magnani’s Select and Test model (1992, 2017). We discuss the fundamental role of abductive hypotheses in experimental medicine and understood in the sense of Bernard (1865, Introduction à l’étude la médecine expérimentale). We conclude with remarks about mechanistic hypotheses discussed by Jenner, in relation to the thesis advocated by Russo and Williamson (2007, Int. Stud. Philos. Sci., 21, 157–170).