Cultures of Knowledge: An Intellectual Geography of the Seventeenth-Century Republic of Letters

Cracow 2009
Educational Reform, Philosophy, and Irenicism

Tomás NEJESCHLEBA
Between Platonism and Aristotelianism: Natural Philosophy of Johannes Jessenius and his Influence on Daniel Sennert

Johannes Jessenius ranks among those thinkers from the turn of the sixteenth and seventeenth centuries who, as was usual in that period, changed their positions and residences often. He was born in Breslau (Wroclaw) in Silesia, studied in Wittenberg, Leipzig and Padua, and worked as a court physician in Dresden, as a professor of anatomy and surgery in Wittenberg, as rector of Wittenberg University, as a physician in Prague, as court physician in Vienna and, finally, as rector of Prague University. He is known primarily as an anatomist who carried out the first public dissection in Prague in 1600 and as a politician at the time of the beginning of the 30 Years War who was executed in Prague in 1621 along with other exponents of the anti-Habsburg policy.

This paper is focused on his philosophical writings. Jessenius was neither an independent nor an original thinker. He even did not create a syncretic or eclectic philosophy. His philosophical works are influenced instead by various philosophical traditions according to the current situation and the thinkers or thoughts he actually came into contact with. He wrote a book called Zoroaster, sive nova, brevis, veraque de universo philosophia (1593) which is particularly influenced by the book by Francesco Patrizi Nova de universis philosophia; it is in fact a transcription and an excerpt from this book. Despite the Platonic and militant anti-Aristotelian orientation of Zoroaster, respectively its pattern philosophy of Patrizi, Jessenius at that same time published certain natural philosophical work by Aristotle (1593) and works by the Aristotelian Girolamo Savonarola (1595). The disputations he presided over in Wittenberg (meaning he was actually the author) were also Aristotelian.

The treatise De sympathiae et antipathiae rerum naturalium causis (1599) also holds an important place among these disputations. The work deals with the question of sympathy and antipathy in more or less the Aristotelian manner, although Jessenius maintains that it was influenced by the ideas of Tycho Brahe, who was more of a Paracelsian thinker. An additional circumstance also influenced the later importance of this dissertation, it having been defended by Daniel Sennert, who was a student of Jessenius and who later replaced Jessenius at the post of professor of anatomy in Wittenberg on the basis of the recommendation of his former teacher. Although Daniel Sennert did not solve the problem of sympathy later in his own works in the same manner as Jessenius, he did develop the orientations included in this dissertation.