At the end of MS.MSL.52B held at the Library at Wellcome Collection, an anonymous treatise concerning acute and chronic diseases, dated to the first century ce., is found. The treatise has survived in two manuscripts in Paris and one in Vienna. The author is commonly known as Anonymus Parisinus (AP). He earned this appellation from his unknown identity and from Paris being the place to which the first manuscript, found originally on Mt. Athos, was brought and identified. This chapter brings to light some of the main features and threads in the author’s medical method and the underlying ideas they reflect. On a handful of occasions AP uses technical causal terminology known from other medical and philosophical sources. The chapter notes some cases of similarity between the ideas or approach of the Anonymous and those of certain medical groups or schools. The limited clinical relevance he assigns seasons, age and gender, resemble the ideas of the Methodists.