[This is a draft of an article in The Dictionary of Eighteenth Century German Philosophers, 3 vols., edited by Manfred Kuehn and Heiner Klemme (London/New York: Continuum, 2010).]
Friedrich Hoffmann (also 'Hofmann') was born on 19 February 1660 in Halle, where he also died on 12 November 1742. Called 'the second Hippocrates' and the 'Aesculapius Hallensis', he was among the most widely read medical authors of the eighteenth century, and is best known for his systematic discussion of the iatromechanical model of medicine — similar to what Hermann Boerhaave (1668-1738) was developing at Leiden — that views the human body as a hydraulic machine wholly governed by mechanical laws.
Hoffmann's father, Friedrich Hoffmann the Elder, was the respected municipal physician of Halle. The younger Hoffmann enrolled at nearby Jena in 1678 (the university at Halle would not open for another fifteen years) where he studied medicine for two years under the iatrochemist Georg Wolfgang Wedel (1645-1721), also attending Caspar Cramer’s lectures on chemistry in Erfurt in 1680. He received his doctorate in medicine from Jena in 1681 (January 31) with a dissertation on suicide (de autochiria), and began lecturing on chemistry (a standard course taught in the medical faculty), but soon left, perhaps pushed out by senior faculty jealous of his teaching success. After practicing medicine in Minden for two years, Hoffmann made an academic tour of Belgium, Holland, and England (during which he met Boerhaave, Thomas Sydenham, and Robert Boyle), returned to Minden in 1684, and assumed various medical offices, eventually being appointed the regional physician for Halberstadt. He married an apothecary's daughter, Anna Dorothea Herstell, on 10 December 1689.
In 1693 he was called to the newly-founded university at Halle as an ally of the Pietist August Hermann Francke (1663-1727), with the charge of organizing its medical school and to serve as its first professor of medicine. (He also became the godfather to Christian Wolff’s first-born son, Friedrich.) Hoffmann recruited his old college friend from Jena, Georg Ernst Stahl (1660-1734), for the second chair of medicine, and the two taught side by side for twenty years, transforming Halle into the preeminent medical school among German-speaking universities. Along with Boerhaave at Leiden, Hoffmann and Stahl were the principal forces behind the medical reforms of the early eighteenth century.
Hoffmann was a member of the German Academy of Natural Scientists Leopoldina (1696), the Berlin Academy of Sciences (he was included in Leibniz’s founding lists and was inducted on 1 April 1701), the Royal Society of London (1720), and the Russian Academy of Sciences in St. Petersburg (1735).
Hoffmann's long career at Halle was interrupted by a call to Berlin in 1709 to serve as personal physician to Friedrich Wilhelm I, but he found court life so disagreeable that he returned to Halle three years later. His colleague Stahl eventually left Halle for good in 1716 to assume this same position at court, and was replaced at Halle by a disciple of his, Michael Alberti (1682-1757). When Stahl died in 1734, Hoffmann was called back to Berlin for eight months.
Hoffmann lectured at Halle on clinical medicine, anatomy, surgery, physics, and chemistry, while Stahl, as second professor, taught theoretical medicine, physiology, pathology, dietetics, pharmacology, and botany. They developed fundamentally opposed medical models — Stahl's animism/vitalism versus Hoffmann's iatromechanism — which, along with their diametrically opposed personalities, eventually led to a bitter estrangement (Hoffmann compares their systems in his posthumously published De differentia, 1746).
Hoffmann's inaugural address at Halle (1693) aimed to disprove atheism on the basis of the artful construction of the human body. Two years later he published his systematic work on iatromechanical medicine (Fundamenta medicinae, 1695; developed more fully in the six-volume Medicina rationalis systematica, 1718-34) — an attempt to carry out a broadly Cartesian program of explaining the human body in wholly mechanical terms (matter and motion), and as part of a deductive system based on first principles. He allowed for chemical processes, but the immediate cause was always to be understood mechanically; and while human beings, unlike other animals, consist of a rational soul (mens) connected to the bodily machine, the basis of life was to be found in the machine itself, not in the rational soul or its connection to the body.
Organic bodies were hydraulic machines consisting of both solid and fluid particles, and life itself was defined as a circular motion of blood in the body. The fluid particles and their respective systems — blood, lymph, and animal spirits — were essential to the working and good health of the organism, and pathologies resulted either from some abnormal mixture in the fluids, or else from the fibers of the vessels carrying these fluids being either too flaccid or too constricted — thus causing an abnormal circulation of the fluids. The animal spirits or sensitive soul (anima sensitiva) — whose function was analogous to what is today understood as the chemical signals transmitted by neurons — was thought of as a kind of aether, extremely fine particles flowing through the nervous system. This aether — the original source of all motion, according to Hoffmann — originated in the sun and was wholly material. A portion of air consisted of aether, which was drawn in through the lungs where it entered the blood and from there was extracted by the brain for use in the nervous system. Similarly, animal heat was a result of motion — not from friction, but from the presence of the aether (De causis caloris, 1699). In more general terms, Hoffmann's work helped shift medical research away from the Galenic model of humors and toward a focus on neuromuscular action and sensibility.
Despite his admiration of Leibniz, Hoffmann borrowed few ideas from him, rejecting his doctrine of pre-established harmony in favor of a version of physical influx between the rational and the sensitive soul (De fato physico, 1724). Hoffmann argued that Leibniz’s doctrine, apart from remaining unproven, involved a double determinism by denying the rational soul and the body the ability to affect each other, and as such was inconsistent with God’s goodness (De potentia, 1729). Hoffmann was convinced of this real connection, however inscrutable it may be (Exercitatio, 1728). A correspondence between Hoffmann and Leibniz was occasioned by the latter’s De ipsa natura (1698), which argued against the Cartesian doctrine of passive matter. In response, Hoffmann sent to Leibniz an essay defending a mechanical understanding of nature and a Cartesian account of animate and inanimate motion based on aether (De natura morborum, 1699). But it was Hoffmann's work in chemistry that most impressed Leibniz, and which occupied much of the correspondence that followed (breaking off in 1707, and published by Hoffmann in 1741 as an appendix to a supplement to his Medicina rationalis systematica). Hoffmann’s chemical investigations included pioneering research on baths, and mineral and sparkling waters, and he was successful in isolating various chemicals (see Partington's detailed account).
In all, Hoffmann authored about 400 publications, mostly brief dissertations and essays, but also the six-volume systematics discussed above, a twelve-volume collection of case studies (Medicina consultatoria, 1721-39), and a nine-volume work on how to live a long and healthy life (Basic Guide, 1715-28), wherein Hoffmann emphasized the restorative effects of proper diet, exercise, clean air, and sleep. He also criticized the diversity and overuse of drugs, and was successful in reducing the pharmacopoeia of his day to a few basic remedies.
De atheo ex artificiosissima corporis humani structura convincendo (Halle, 1693).
Fundamenta medicinae (Halle, 1695; English trans. by Lester King, New York, 1971).
Gründliche Wegweisung, wie ein Mensch vor dem frühzeitigen Tode und allerhand Krankheiten, durch ordentliche Lebens-Art sich verwahren könne, 9 vols. (Halle, 1715-28).
Medicina rationalis systematica, 6 vols. (Halle, 1718-34; English transl. 1783).
Medicina consultatoria, worinnen unterschiedliche über einige schwere Casus ausgearbeitete Consilia, auch Responsa Facultatis Medicae enthalten, 12 vols. (Halle, 1721-39).
Opera omnia physico-medica, 6 vols. (Geneva, 1740), plus three supplemental volumes (Geneva, 1749-53).
De causis caloris (Halle, 1699).
De natura morborum medicatrice mechanica (Halle, 1699).
De diaboli potentia in corpora (Halle, 1703).
Gründliche Untersuchung von der Pest, Uhrsprung und Wesen, nebst angehängten Bedenken, wie man sich vor selbiger praeserviren, und sie sicher curiren könne? (Berlin, 1710).
De fato physico et medico eiusque rationali explicatione disquisitio (Halle, 1724).
Exercitatio de optima philosophandi ratione (Halle, 1728). Reprinted in 1741 with Hoffmann’s Leibniz correspondence.
De potentia et impotentia animae humanae in corpus organicum sibi junctum (Halle, 1729).
Commentarius de differentia inter ejus doctrinam medico-mechanicam, et Georgii Ernesti Stahlii medico-organicam (Frankfurt/Main, 1746).
ADB, vol. 12, pp. 584-88 (August Hirsch).
DBE, vol. 5, p. 117 (Ingo Müller).
DSB, vol. 6, pp. 458-61 (Guenter B. Risse).
Dunkel, Johann Gottlob Wilhelm, Historisch-kritische Nachrichten von verstorbenen Gelehrten und deren Schriften (1753), vol. 1, pp. 89-93, 344, 720-21.
Hoffmann, Paul, 'La théorie de l'âme dans la medicina rationalis systematica de Friedrich Hoffmann', in Revue de synthèse, vol. 105 (1984), pp. 55-82.
Jöcher/Adelung (Leipzig, 1787), vol. 2, pp. 2056-70.
Kaiser, Wolfram, 'Der hallesche Ordinarius Friedrich Hoffmann (1660 bis 1742) als Initiator der modernen Balneo- und Hydrotherapie', in Zahn-, Mund-, und Kieferheilkunde mit Zentralblatt, vol. 63 (1975), pp. 580-92.
King, Lester S., 'Stahl and Hoffmann: A Study in Eighteenth-Century Animism', in Journal of the History of Medicine and Allied Sciences, vol. 19 (1964), pp. 118-30.
—, 'Medicine in 1695: Friedrich Hoffmann's Fundamenta Medicinae', in Bulletin of the History of Medicine, vol. 43 (1969), pp. 17-29.
— The Philosophy of Medicine (Cambridge, Mass., 1978).
Konert, Jürgen, 'Academic and practical medicine in Halle during the era of Stahl, Hoffmann, and Juncker', in Caduceus, vol. 13 (1997), pp. 23-38.
Müller, Ingo Wilhelm, Iatromechanische Theorie und ärztliche Praxis im Vergleich zur galenistischen Medizin: Friedrich Hoffmann, Pieter van Foreest, Jan van Heurne (Stuttgart, 1991).
— 'Friedrich Hoffmann (1660-1742)', in Klassiker der Medizin, ed. by Dietrich von Engelhardt and Fritz Hartmann (Munich, 1991), vol. 1, pp. 202-14.
NDB, vol. 9, pp. 416-18 (Hans-Heinz Eulner).
Partington, J. R., A History of Chemistry (London, 1961), vol. 2, pp. 691-700.
Rothschuh, Karl E., 'Studien zu Friedrich Hoffmann (1660-1742)' in Sudhoffs Archiv für Geschichte der Medizin und der Naturwissenschaften, vol. 60 (1976), pp. 163-93, 235-70.