CHAPTER THREE

JACOB SCHEGK ON THE PLASTIC FACULTY AND THE ORIGIN OF SOULS

1. Introduction

In the conclusion of his embryological treatise On the Formation of the Fetus, avowed to be ignorant of the cause which forms the fetus. Although he recognized the efffects of the highest intelligence and force in fetal formation, he did not believe the soul itself, presumed to reside in the seed, to be capable of constructing the fetus: I admit my puzzlement on the subject of the substance of the soul. I am unable even to reach the level of a probable statement in this regard. And so I confess that I do not know the cause of the construction of the fetus. For I observe in this construction the utmost intelligence and power, and I cannot allow that the soul in the seed [. . .] constructs the fetus, since this kind of soul is not only unintelligent but entirely devoid of reason.1 Inspired by this argument, Leoniceno wrote On Formative Power. This small monograph analyzed existing views on the notion of “formative power” (virtus formativa), which physicians thought to be responsible for fetal formation. Indeed this notion, which Galen had originally formu- lated by the term “molding faculty” (dunamis diaplastiké), was in vogue during the Middle Ages as an explanation of the formation not only of living beings but also of natural things in general. Leoniceno particularly criticized the interpretation of Averroes and Pietro d’Abano by appeal- ing to ancient Greek commentators of such as Simplicius, whose texts were newly made available in the Renaissance. Leoniceno’s discus- sions were marked by a strong philological flavor and opened up a new era of intense debates in embryology. Against his naturalistic interpre- tation of the formative power, Fernel developed a fully Platonizing idea of the “divine formative force” regulating the generation of living beings through his influential work On the Hidden Causes of Things. Likewise, the notorious Aristotelian Julius Caesar Scaliger (1484–1558) spoke of a “divine

1 Galen, De foetuum formatione, 6 (Kühn, IV: 700 = Nickel, 104). jacob schegk 81 force” working in the generation of living beings in his extremely popular treatise Exotericae exercitationes (Paris, 1557).2 The theory of the plastic faculty, advanced by Jacob Degen alias Schegk (1511–87), must be understood within this historical and intellectual con- text.3 A native of Schorndorf near Stuttgart in Württemberg, an accom- plished humanist and a moderate Lutheran, he fijirst taught philosophy, and later , at the Protestant University of Tübingen for several decades. Although he remains very little known to historians, his uni- versity lectures were highly popular and attracted many students com- ing from reformed lands. Even though Schegk is mainly remembered as a commentator of Aristotle, he was also keenly interested in medical and biological issues. Among other writings he composed an embryological treatise On the Plastic Faculty of the Seed (De plastica seminis facultate) (Strasbourg, 1580). This was the fijirst Renaissance work that explicitly applied the expression “plastic faculty” ( facultas plastica) to the Galenic notion of formative power with the use of the very term “plastic.”4 Although this treatise is now relatively scarce, Schegk’s theory was to become widely known among Protestant natural philosophers such as Daniel Sennert (1572–1637) and Johann Amos Comenius (1592–1670) in the early seventeenth century.5 William Harvey (1578–1678), in his turn, drew on this theory for developing his idea of “plastic force” (vis plastica)

2 Julius Caesar Scaliger, Exotericae exercitationes, ex. 6.5 (Vascosan, f. 14r). Cf. Guido Giglioni, “Girolamo Cardano e Giulio Cesare Scaligero: il dibattito sul ruolo dell’anima vegetativa,” in Girolamo Cardano: le opere, le fonti, la vita, ed. Marialuisa Baldi and Guido Canziani (Milan, 1999), 313–39, esp. 319. 3 On his life and work, see Dictionary of Scientifijic Biography 12 (1975), 150–51; Christoph Sigwart, “Jakob Schegk, Professor der Philosophie und Medizin,” in idem, Kleine Schriften (Freiburg im Breisgau, 1889), 256–91; Charles H. Lohr, Aristotle Commentaries: II. Renaissance Authors (Florence, 1988), 410–12; Sachiko Kusukawa, “Lutheran Uses of Aris- totle: A Comparison between Jacob Schegk and Philip Melanchthon,” in Philosophy in the Sixteenth and Seventeenth Centuries: Conversations with Aristotle, ed. Constance Blackwell and Sachiko Kusukawa (Aldershot, 1999), 169–88. On in sixteenth- century Tübingen, see among others Charlotte Methuen, Kepler’s Tübingen: Stimulus to a Theological Mathematics (Aldershot, 1998). 4 I have used the following edition: Jacob Schegk, De plastica seminis facultate libri tres (Strasburg, 1580), indicated hereafter as PSF. It was recently digitized by the BIU Santé for the project “The Medical Context of the Scientifijic Revolution.” Cf. Walter Pagel, New Light on William Harvey (Basel, 1976), 100–103. Nevertheless, see also Scaliger’s passing formula- tion in his Exotericae exercitationes, ex. 101.17, f. 151v. 5 Daniel Sennert, De chymicorum cum Aristotelicis et Galenicis consensu et dissensu (Wittenberg, 1619), 1.9. See its second edition (Wittenberg, 1629), 95–98, also digitized by the BIU Santé. On Comenius, see Guido Giglioni, “Spiritus Plasticus between Pneuma- tology and Embryology (A Note about Comenius’ Concept of Spirit),” Studia comeniana et historica 24 (1994), 83–90.