In the history of early modern science, the German physician Andreas Libavius (Halle, Saxony, c.1550–Coburg, Bavaria, 1616) is known for having promoted the institutionalization of alchemy in the academic sphere along with the creation of laboratories and instruments. Libavius was also remarkable for his extended network of scholarly friends and foes. On the one hand, he developed a vast epistolary work in connection with the medical Republic of Letters in the Holy Roman Empire. On the other hand, he was a relentless opponent of the Paracelsian philosophy. For this reason, many of his works are polemical treatises aimed at Paracelsian physicians. While blaming the latter for their difficult terminology and confusing discourse, Libavius was constantly insisting on the importance of logic in the organization of knowledge and argumentation. With this in mind, he sought to demonstrate the longstanding compatibility between alchemy, Aristotelian natural philosophy, and Galenic medicine in order to counter the Paracelsian rupture with the tradition. Moreover, Libavius expounded an account of elements and principles which operated in both alchemical and medical contexts. In this regard, he contributed an innovative theory of matter drawing on the Aristotelian notion of matter–form and Democritean atomism—an eclectic interpretation which influenced Daniel Sennert.