This article discusses a Latin manuscript that can be found in the Jan Baptist Van Helmont (1579–1644) archives in Mechelen (Malines), Belgium. The manuscript bears no author and no title, and begins with the words ‘Exterior homo’, hence being referred by this provisional title in the analysis. Ecclesiastical prosecutors investigating Van Helmont for heresy in 1634 considered that it was written by him, but this was vehemently denied by the Flemish physician. The present article takes a first detailed look at the content of the treatise and ideas contained therein. It hence identifies the manuscript as belonging to a seventeenth-century physician influenced by the ideas of Theophrastus Paracelsus (1493–1541) and his interpreter Petrus Severinus (1542–1602), and containing a complex medical philosophy drawn on alchemical thought. Thus, the anonymous author presents a comprehensive view on the nature and structure of man, as well as an idiosyncratic theory of human generation. Following the analysis of the treatise, the article further compares it with the known works of J.B. Van Helmont, and finds that it is very similar to his ideas. Hence, the article concludes that it is ‘likely’ that the manuscript is indeed written by Van Helmont, although lack of direct evidence prevents certain attribution.