Gilbert Jack was a sixteenth-century philosopher and physician who was born in Scotland but eventually attained celebrity in the Netherlands as one of the Low Countries’ most famous metaphysicians.
Gilbert Jack (Jacchaeus) (Aberdeen, 1578–Leiden, 18 April 1628) was a reformed Scottish philosopher (Schmutz) who left a lasting mark on Dutch thought. Both a physician and metaphysician, Jack began his studies in Aberdeen and then continued his education at Marischal College under the direction of Robert Howie (Pyle, 463). Jack completed his education at Marischal in 1597 and in the following year moved to Germany to pursue further education at the University of Helmstedt in 1598 (ibid.). With his philosophical course of studies completed, in 1603, Jack moved to the Netherlands and enrolled at the University of Leiden, where, like his mentor Howie, the Scotsman took up theology (ibid.). Leiden would eventually become Jack’s academic home, and he was first appointed as a Professor Extraordinarius of logic in 1605. This was followed in 1617 by an appointment to a chair in physics, which he held until his death in 1628 (ibid.). At Leiden, Jack counted among his students Cartesians and anti-Cartesians alike, including Heidanus, Reneri, Voetius, and Burgersdijk (Schmutz).
Jack’s first work was his 1614 Institutiones physicae. The volume opens with a prefatory treatment of the nature of philosophy in general (c. 1), which, because of man’s own faculties of intellect and will, is subject to division within itself (fols. 1, 2); the division of philosophy into natural, moral, and rational or, what is the same, the more familiar speculative and practical philosophy (c. 2); the nature of “contemplative philosophy,” which he subdivided into metaphysics, physics, and mathematics (c. 3); and, finally, the constitution of natural philosophy or physics (c. 4), which has as its main consideration motion and pursues the principle of motion that all natural things have in themselves (fol. 7).
The first book of the treatise De corporis naturalis principiis internis, as its title suggests, explores at length the nature of the principles of corporeal things. It begins with a discussion of the nature of a principle in general (c. 1) before taking up in succession the three Aristotelian principles of motion: (prime) matter (c. 2), form (c. 3), and privation (c. 4). Book two of the Institutiones physicae addresses the concept of “nature,” its definition, activities and passivity, distinctions from art, and causality. The third book treats of motion, while the fourth book explores the nature of time. The fifth book offers Jack’s astronomical thinking and discusses the movements of the heavens and celestial orbits. Book six concerns “mixed bodies” (de corpore misto) and contains discussions of the number of and nature of the elements, “first qualities,” alteration, generation, corruption, and even putrefaction. Book seven contains Jack’s meteorology in which there is discussion of meteors, thunder, rain, comets, the Via Lactea or Milky Way (c. 8), wind, rainbows, etc. In the eighth and final book, Jack addresses the nature of the soul. Here, Jack discusses embryonic gestation vis-à-vis vegetative, sensitive, and rational ensoulment.
Ten years later, in 1624, Jack authored his final treatise, a medical tract that explores a variety of topics related to the medical arts across six books. As is to be expected, the opening book addresses the nature of medicine in general, which he identifies in a threefold manner, namely, the “subject… division, and end” (fol. 1). Also unsurprisingly, Jack identifies the cure of the human body as the subject of medicine (ibid.). Thus, he says, while it is certainly the case that the human is considered within ethics, physics, and theology, in none of those sciences is the human being considered in relation to health (fol. 2). Subordinate to physics as a lower science and drawing its principles from the conclusions of physics, medicine pertains not only to the human body but also to the instruments (e.g., plants, metals, etc.) that produce health (fol. 2). The end of medicine is equally as obvious as its subject, namely, health and its preservation if it is already present or its restoration if it is absent (fol. 3). The remainder of the work addresses various illnesses (book 2), different kinds of symptoms and their causes (book 3), physiological signs of health (e.g., pulse, urine) and disease (book 4), the application of medication and medical treatments (book 5), and nourishment (book 6).