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Hoffmann and Stahl at the University of Halle

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Hoffmann portrait.
Courtesy of the National Library of Medicine.

Worth had five works by Friedrich Hoffmann (1660-1742), including his Exercitatio medico-chymica de cinnabari antimonii ejusque eximiis viribus (Leiden, 1685) and Observationum physico-chymicarum selectiorum libri III (Halle, 1722) and one by his colleague Georg Ernst Stahl (1659-1734), the Fundamenta chymiae dogmaticae & experimentalis (Nuremberg, 1723). Both had been students at the University of Jena before becoming members of the teaching staff at the University of Halle and both were members of the Pietistic movement. It was on Hoffmann’s recommendation that Stahl was elected to the second chair of medicine at the relatively new university of Halle, which had been founded in 1694 but, as De Ceglia relates (2007), there is a suggestion that Hoffmann had actually wanted to appoint Stahl’s older brother Georg Konrad, an up-and-coming iatro-mechanist, rather than the younger Stahl who had already criticized some of Hoffmann’s work.

If Hoffmann had misgivings about the appointment of the younger Stahl the first few years of Georg Ernst’s teaching at Halle may have allayed them, for peace ensued. Unfortunately it didn’t last for long. In the admittedly biased words of Hoffmann’s autobiography, Stahl ‘never neglected to ambush and attack constantly, with acrimony and recourse to ludicrous expressions, anyone who referred to mechanical medicine’. The heart of the dispute concerned pulse-rates. For the animist Stahl, Hoffmann’s mechanistic understanding of medicine simply didn’t make sense. Stahl argued that organic matter was of a passive nature and inherently chemically unstable. Without some sort of spirit it would quickly decompose. That being said, there was, as Chang (2002) suggests, some basic level of agreement on the corpuscular concept of chemical principles. Hoffmann in particular was very much influenced by Robert Boyle’s corpuscular theories in chemistry and had travelled to England, meeting Boyle in London in 1684. He later became a Fellow of the Royal Society in 1719. As Debus (2001) suggests, Hoffmann’s Observationum Physico-Chemicorum Selectiorum of 1722 demonstrates that Hoffmann was well acquainted with the works of iatrochemists and many of the authors he references in this book were collected by Worth: Paracelsus, Isaac Hollandus, Basil Valentine and Glauber, not to mention Boyle. Ultimately, though, he was far more concerned with a mechanistic understanding of medicine and, in the words of Debus, ‘sought to separate chemistry and medicine’.

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Stahl portrait.
Courtesy of the National Library of Medicine.

Georg Ernst Stahls’s most imporant work was his Fundamenta chymiae dogmaticae & experimentalis, which he published at Nuremberg in 1723. It was, as he tells us himself in the preface, based on lecture notes taken down by students at the University of Jena and it therefore gives us a glimpse of what type of chemical teaching Stahl was engaged in when he was a privatdozent at Jena in the 1680s. In the Fundamenta chymiae dogmaticae & experimentalis (Nuremberg, 1723) Stahl sets out his chemical principles in the following manner:

  1.  Universal Chemistry is the Art of resolving mixt, compound, or aggregate Bodies into their Principles; and of composing such Bodies from those Principles.
  2.  It has for its Subject all the mix’d, compound, and aggregate Bodies that are resolvable and combinable; and Resolution and Combination, or Destruction and Generation, for its Object.
  3.  Its Means in general are either remote or immediate; that is, either Instruments or the Operations themselves.
  4.  Its End is either philosophical and theoretical; or medicinal, mechanical, oeconomical, and practical.
  5.  Its efficient Cause is the Chemist.
  6. This noble Art was, in several branches of it, very early cultivated. Tubal-cain the Son of Cain is by Moses propos’d as its Inventor. It was very commonly known, particularly to the Egyptians, in the first Ages. And among those who have principally excell’d therein of late, are Isaac Hollandus, Basil Valentine, Arnoldus de Villa nova, Raymond Lully, Trithemius Spanheim, Paracelsus, Helmont, Zwelfer, Becher, and Boyle. In that part of it called Alchemy, Alexander von Suchten, Gasto Dulcon Claveus, but particularly Philaletha, deserve the perusal.
  7. In order to acquire this Art, its Scientifical Elements must be well understood; and its Operations personally view’d, and manually perform’d: when its two Parts, of Theory and Practice.
  8. Its Theory, in general, is acquired by Information, axiomatically and demonstratively delivered in the synthetical manner, à priori; but analytically, and à posteriori, in particular.
  9. Its Practice is acquired by a careful Instruction in the proper manual Operations; which, in general, are limited by place, time, the subject and suitable means; and in particular, by the manner of performing. George Ernst Stahl, Philosophical Principles of Universal Chemistry (London, 1730), preliminaries, pp 1-2.

Oldroyd (1973) argues that Stahl’s textbook fits neatly into aristotelian scholastic  tradition though it diverged in some areas (most notably concerning the understanding of the motion of matter). Aristotelian scholasticism may have provided an overall framework, but Stahl had many other scholarly debts. We see this when we examine his concept of matter: in effect, Stahl’s chemical understanding represented a pyramid, with water and three kinds of earth at the base; next were the ‘mixts’; above these were the compounds and finally, at the pinnacle, the superdecompositas or aggregates. This four level understanding of matter was not new for Stahl’s theory owed much to Johann Joachim Becher’s Physica subteranea (Frankfurt, 1667), a work which Stahl had republished in 1703.  Stahl’s three types of earth likewise corresponded with earlier principles such as salt, sulphur and mercury. It was from the second of these that he derived his most famous (though incorrect) phlogiston theory of combustion. Even here there were echoes of the past. As Chang (2002) points outs, Stahl’s linkage of the material base of phlogiston to grease, fat and inflammability, held paracelsian overtones for paracelsian chemists had connected these to sulphur (Stahl’s second ‘earth’). However, unlike the paracelsians, Stahl argued that phlogiston was not an active principle. For Stahl, matter might be in motion but it was essential passive in nature.

Both Stahl and his counterpart at Leiden, Herman Boerhaave, in their own ways represented a departure from the iatro-chemical school. Stahl would have stongly disagreed with Boerhaave’s mechanistic understanding of medicine but both were keen to highlight the importance of chemistry for its own sake. Far from being a handmaiden of medicine for Stahl, chemistry was to be viewed as one of the physical sciences. As Debus (1992) points out, Stahl’s textbook, the Fundamenta Chymia, says hardly anything about medicine, concentrating instead on considerations of matter and descriptions of chemical processes.

Sources

Chang, Ku-ming (2002), ‘Fermentation, Phlogiston and Matter Theory: Chemistry and Natural Philosophy in Georg Ernst Stahl’s Zymothecnia Fundmentalis’, Early Science and Medicine 7, no.1, 31-64.

Debus, Allen G. (1986), ‘Chemistry and the Universities in the Seventeenth Century’, Academiae Analecta: Klasse der Wetenschappen, 48, 15-33 (30-31).

Debus, Allen G. (1992), ‘Alchemy and Iatrochemistry: Persistent Traditions in the 17th and 18th Centuries’, Química Nova 15 (3), 262-68.

Debus, Allen G. (2001), Chemistry and Medical Debate. Van Helmont to Boerhaave (Science History Publications).

De Ceglia, Francesco Paulo (2007), ‘Hoffmann and Stahl. Documents and Reflections on the Dispute’, History of Universities XXII (1) , 98-140.

Oldroyd, David (1973), ‘An Examination of G. E. Stahl’s Philosophical Principles of Universal Chemistry’, Ambix, 20, 36-52.

Smets, Alexis, ‘The controversy between Leibniz and Stahl on the Theory of Chemisty’, Neighbours and Territories. The Evolving Identity of Chemistry. 6th International Conference on the History of Chemistry, pp 281-306. Available here

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Zacharias Brendel, Chimia in artis formam redacta… (Leiden, 1671), titlepage.

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