The notion of enlightened medicine was conceived by an elite group of eighteenth century medical scholars to which Tissot belonged. This elite group sought to create an identity separate from its counterpart, that is to say popular medicine as defined by this group. The distinctive characteristic of this enlightened medicine was its critical rationalism based on observation and experiment as well as their numerical evaluation. This article describes how Tissot, influenced by Fr. Boissier de Sauvages, Albrecht von Haller and J.G. Zimmermann, understood observation and experiment in medicine. This study shows that learned medicine, as portrayed by our author, seems to have originated today's modern scientific medical approach