Daniel Sennert on Poisons, Epilepsy, and Subordinate Forms Andreas Blank University of Paderborn This article explores some connections between the medical conception of poi- son-induced epilepsy and the ontological conception of a plurality of substan- tial forms in living beings in the work of the Wittenberg physician and phi- losopher Daniel Sennert (1572–1637). It does so by taking a developmental approach, tracing Sennert’s responses to some of his predecessors such as Jean Fernel, Petrus Severinus, and Julius Caesar Scaliger. Sennert’s responses to Fernel indicate that Sennert does not regard poison-induced epilepsy as a disease that affects the dominant form of a living being. His responses to Severinus indicate that he also does not reduce the agency of epilepsy-inducing poisons to chemical causation. His responses to Scaliger indicate that he as- signs to subordinate forms in the human body a central role in explaining the occurrence of auto-generated poisons leading to epileptic ªts. At the same time, Sennert substantially goes beyond Scaliger by applying some of Severinus’s in- sights concerning analogies between species degeneration and the generation of disease to the case of epilepsy. I. Introduction As Peter Niebyl has documented, one of the issues in which the Wittenberg-based physician and philosopher Daniel Sennert (1572–1637) departed from Paracelsus and his followers was the concept of disease. Paracelsus and some of his followers regarded diseases as real beings— so-called “disease-entities” (entia morbis) that can enter into the body of a living being and thereafter possess a clearly deªned location in the affected organism.1 For Sennert, such a view is a dangerous confusion between dis- 1. On entia morbis in Paracelsus, see Pagel 1982, pp. 134–144. On entia morbis in the Paracelsian tradition, see Pagel 1984, pp. 19–23, 46–48. Allen G. Debus has pointed out Perspectives on Science 2011, vol. 19, no. 2 ©2011 by The Massachusetts Institute of Technology 192 Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/POSC_a_00036 by guest on 30 September 2021 Perspectives on Science 193 ease and its causes. According to him, causes of disease can be present in an organism without actually causing a disease (Sennert 1629, p. 253). Moreover, he shares the traditional Christian doctrine according to which all created substances are intrinsically good, such that intrinsically bad “disease-entities” could not be part of creation (p. 259). To be sure, for many contagious diseases Sennert invokes the agency of “seeds,” to which he ascribed a corporeal nature.2 But he categorizes them as causes of dis- ease, not as diseases themselves. Disease, in his view, is nothing but an im- pairment of the normal functioning of the organism or, as he puts it, “a praeternatural quality induced in the body, on account of which the body is so disposed that the functions it ought to perform are impaired” (Niebyl 1971, p. 127).3 At the same time, Sennert has deªnite views as to what kinds of beings the causes of disease are and what kinds of beings the organisms affected by these causes are. In this essay, I will explore some of these ontological issues with respect to Sennert’s views on poisons and epilepsy. Sennert shares with other early modern thinkers the view that epilepsy is caused by “an aura or a vapour, or poisonous matter” (aura vel vapor, vel materia venenata) which is either generated in the brain or transmitted there from other parts of the body (Sennert 1656, 2:302).4 He also shares with other early modern thinkers the view that, while each living being has a single substantial form, its body contains a large number of corpuscles that have their own substantial forms. Thanks to pioneering studies by Emily Mi- chael, the intricate details of Sennert’s theory of a plurality of hierarchi- cally ordered substantial forms in living beings are well known by now that some of Paracelsus’ early followers tried to reconcile Paracelsian and Galenic ideas (see Debus 1991, pp. 19–21). In many respects, if not on the issue of entia morbis, Sennert’s 1619 De chymicorum cum Aristotelicis et Galenicis consensu ac dissensu is another instance of such a conciliatory approach. 2. Sennert follows the theory of contagion developed by Girolamo Fracastoro (1478– 1553), when he deªnes a contagium as “a certain body ºowing from a contagious body and capable of causing a similar disease when received by another body” (corpus quoddam e corpore contagioso efºuens, & in alio receptum similem morbus in eo excitare valens) (Sennert 1656, 2:146). On Fracastoro’s theory of contagion, see Nutton 1983; Nutton 1990; Pennuto 2008, ch. 8. On Sennert’s relation to Fracastoro, see Newman 2006, pp. 143–144. 3. The quotation is from Sennert 1619, p. 445 (Niebyl’s translation). The concept of disease, of course, is not the only topic on which Sennert disagreed with the Paracelsians. Pagel has emphasized that “the basic error of Paracelsus according to Sennert lies in his re- jection of the humors, the very existence of which he sometimes denied” (Pagel 1982, p. 341). Sennert also was critical of the Paracelsian reliance on intuitive insight in medi- cine (see Eckert 1992). 4. On early modern theories of vapor-induced epilepsy, see Temkin 1971, pp. 198–201. Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/POSC_a_00036 by guest on 30 September 2021 194 Daniel Sennert on Poisons, Epilepsy, and Subordinate Forms (Michael 1997; 2001).5 However, some connections between his ontology of dominant and subordinate forms and other issues in his biological and medical thought have not yet been explored as fully as they deserve to be. This holds especially for Sennert’s responses to predecessors who, in their biological and medical works, also upheld a plurality of forms in living beings, such as the doyen of the Paris medical faculty, Jean Fernel (1497– 1558), the Danish royal physician Petrus Severinus (1540/2–1602), and the Agen-based physician and philosopher Julius Caesar Scaliger (1484– 1558). I shall argue that certain aspects of Sennert’s responses to different ver- sions of a theory of a plurality of forms in living beings sheds light on three issues central to Sennert’s discussion of poisons and epilepsy. In fact, taken together, these responses tell an interesting developmental story about how Sennert constructed an account of poisons and epilepsy that is closely connected with the ideas of his predecessors but nevertheless di- verges substantially from some aspects of the thought of his predecessors. The response to Jean Fernel’s theory of “diseases of the whole substance” in Sennert’s Institutiones medicinae (1611) will make clear why Sennert sub- sumes epilepsy under his concept of disease as an impairment of the nor- mal functioning of the organism rather than an impairment of the sub- stantial forms of the parts of the organism (section 2). The response to Petrus Severinus’s theory of chemically operating “seeds of disease” in Sennert’s De chymicorum cum Galenicis et Aristotelicis consensu ac dissensu (1619) will make clear why Sennert assumed that the subordinate forms relevant in causing epilepsy operate not only in the way in which chemical substances work but in other ways as well (section 3). The response to Jul- ius Caesar Scaliger’s discussion of the mutability of biological species in Sennert’s Practica medicina VI (1635) will make it clear to what extent Sennert’s explanation of the origin of auto-generated poisonous vapors is modelled on early modern theories of biological reproduction (section 4). Taken together, Sennert’s responses to his predecessors illuminate some ways in which his views on poisons and epilepsy are connected with his biomedical ontology. II. Poisons, Epilepsy, and Diseases of the Whole Substance As William Newman has brought to light, Fernel’s theory of diseases of the whole substance was the topic of a disputation by Sennert’s academic teacher, Johann Jessenius, which Sennert undertook to defend in 1596 5. On the plurality of forms in Sennert, see also Emerton 1984, pp. 64–65; Arthur 2006. Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/POSC_a_00036 by guest on 30 September 2021 Perspectives on Science 195 (Newman 2006, pp. 139–140).6 While it is clear that Sennert was familiar with this issue from early on, his Institutiones medicinae (1611) contains de- tailed discussions of Jean Fernel’s De rerum abditis causis (1548) which indi- cate that Sennert had become highly critical of some aspects of the theory of the whole substance. While many of Sennert’s later views concerning the causes of epilepsy are not yet fully developed in the Institutiones medi- cinae, the general outlook on epilepsy outlined here remains in place in his later writings, and some of the features that remain constant throughout the following years are connected with his early response to Fernel. In the Institutiones medicinae, Sennert adopts Fernel’s arguments that favor a vapor theory of epilepsy over a Galenic obstruction theory. According to the ob- struction theory, epilepsy is caused by some solid and tenacious humour (crassus & viscosus humor) blocking the ventricles (ventricula) and pores (meatus) of the brain. Thereby, epilepsy is likened to apoplexy—the para- lyzation of body parts through the obstruction of the corresponding brain regions (Fernel 2005, pp. 637–639).7 Fernel’s and Sennert’s ªrst objection is: If an obstruction of the ventricles of the brain were the cause of epi- lepsy, one would expect that every epileptical ªt would be followed by ap- oplexy, or every case of apoplexy be preceded by an epileptical ªt, neither of which is the case (pp.