Stahl, Georg Ernst
Stahl, Georg Ernst (1660-1734) German medical scientist and chemist.
Stahl was originator of the phlogiston theory in chemistry and an advocate of vitalism. He studied at the University of Jena where he received a medical degree in 1684. In 1694 he joined Friedrich Hoffmann (1660-1742) at the newly established University of Halle, which soon became a leading medical school. In 1715, he moved to Berlin as court physician for Frederick William I of Prussia. He remained there until his death in 1734. Stahl’s work is shaped by the seventeenth century rebellion against traditional science which took place when traditional religion was still powerful, with piety and orthodoxy as strong values. Stahl was a devout Pietist himself and the university of Halle was an important center combining Pietism and rationalism.
Stahl did not produce a systematic exposition of his thought. However, three general principles can be distinguished that dominated his thought. First, he argued for an irreducible difference between mind, or anima, and matter. What characterizes mind is an immaterial vital principle. It is the possession of this vital principle that distinguishes the living from the the non-living. Second, Stahl held a teleological view of this anima, arguing that living creatures can be understood only if attention is paid to their striving to particular ends. Third, Stahl held that nonliving things are fully mechanical and living things are partly mechanical. The anima exerts itself through mechanical principles by bringing and keeping a material body in motion, most particularly the heart and the circulation of blood. By holding that motion is a part of the anima that is superimposed on matter, Stahl seeks to solve the Cartesian crux of how something immaterial can act upon something material. If motions become impaired the body becomes diseased and may even die. Consequently, Stahl considered the central task of medicine the clinical study of physiological processes. Healing is essentially aiding the body in executing its natural processes. By advocating a mechanical view of body and a teleological view of mind, Stahl combined an analytic approach to matter with a holistic approach to mind. As a result of this, Stahl moved away from detailed anatomical and chemical studies in medicine, as it drew the attention away from the body as a purposive whole.
In chemistry Stahl opposed the atomist mechanical explanations that treat all atoms as equal. Instead Stahl argued along Aristotelian lines for qualitatively different atoms. Drawing heavily on Johann Becher (1635-82), Stahl distinguished three elementary principles: air, water and earth. Earth was further divided into three components, one of which being responsible for combustion. Following Becher, Stahl argued that combustibility is not a quality but is a substance or element that is capable of existing in isolation in a relatively pure form. For this type of earth Stahl reserved the term Phlogiston. In the second half of the eighteenth century the phlogiston theory was discredited by Lavoisier, Antoine Laurent.
Strube, Irene, Georg Ernst Stahl, 1984.
Cornelis de Waal
Indiana University-Purdue University Indianapolis