Bruce T. Moran
University of Nevada

Chemical Medicine (sometimes referred to in the early modern era as chymiatria or iatrochemistry) combines components of medicine that are physiological (specific chemical views of how the body functions), therapeutic (the means of treating diseases whose origins are understood in chemical ways), and pharmaceutical (making medicines from natural substances including minerals and metals by means of laboratory processes utilizing heat at high temperatures). The most important figure in combining these parts of chemical medicine is the sixteenth century Swiss-German physician and alchemist, Paracelsus (1493–1541).

In books such as The Great Surgery, and some with unusual titles like the Opus Paramirum (Work Beyond Wonder) and Paragranum, Paracelsus described the human body (the microcosm) as a condensation of the powers of the entire universe (the macrocosm). The processes of human life were the processes of nature, and the vital functions of both nature and the body operated chemically. Underlying all physical creation were the primary principles (the tria prima) of Sulphur, Salt, and Mercury. Everything in nature also possessed, Paracelsus thought, virtues or powers derived from the stars. These astral powers became concentrated in specific things, and extracting those powers from animals, plants, minerals, and metals through an array of laboratory processes, above all distillation and sublimation, became a primary occupation of Paracelsian chemical pharmacy.

That idea was not new. Extracting the spiritual stuff of the heavens, in the form of a “fifth essence,” and by means of distillation, was already well established in late medieval and renaissance alchemical practice. What Paracelsus introduced was a new, chemical reason for making medicines in this way. Disease, he argued, arose not as a result of a general imbalance of humors in the body as required by traditional medical thinking. Instead, he argued, diseases possessed specific, chemical etiologies and affected, not the body in general, but specific, localized parts. The body was a repository of virtues, and was constantly involved in separating life-giving, spiritual powers from raw matter. When the body’s internal alchemist failed in that chemical separation, or failed to do so completely, illnesses followed, exhibiting symptoms that were sulphureous (inflammations, fevers), mercurial (excess moistures), or saline (e.g. eruptions of the skin). Grasping what specific virtues were required to replenish what the body was lacking, recognizing where to find those corresponding virtues in the objects of the greater world, and knowing how to extract and enhance them through laboratory procedures, were each required of chemical physicians as part of therapeutic practice.

Drawing upon preexisting traditions in the Renaissance, partly magical, partly empirical, Paracelsus believed that each thing in the larger world revealed, by way of its physical characteristics and properties, the kinds of medicinal virtues it possessed. Those characteristics also indicated the kinds of illness (sulphureous, mercurial, saline) that specific substances could be used to treat, following the extraction and application of their virtues in order to restore the virtues that the body’s own chemistry had failed adequately to produce. In this way, like cured like. The virtues extracted from plants and animals served to make some medicines, but the virtues found in minerals and metals, because they were fixed to a greater degree and thus remained effective through laboratory extractions involving excessive heat, were often desired as remedies when responding to severe, advanced, and entrenched disease.

The physiological and therapeutic traditions linked to Paracelsus influenced chemical-medical philosophies throughout the seventeenth century; physicians and natural philosophers might adopt some aspects of Paracelsian thinking but reject others. The writings of the Flemish physician, philosopher, and chemist, Jan Baptiste van Helmont (1579–1644), collected together and published posthumously in 1648 with the title Ortus medicinae (Origin of Medicine), stand out prominently in this regard (for a related work in English see Van Helmont’s works (1664). While rejecting some aspects of Paracelsus’s view of nature, especially the notion that Sulphur, Salt, and Mercury were preexisting principles guiding all of creation, van Helmont nevertheless advanced a medical philosophy focused upon the activity of vital spirit in nature, and advanced techniques for preparing chemical medicines, especially preparations involving mercury. Following a tradition advanced by early followers of Paracelsus, he considered diseases to arise from preformed spiritual seeds, and developed the notion that fermentation was an essential physiological process, arguing as well that acid was the digestive agent in the stomach and that alkali acting upon acid exhibited neutralizing effects.

Those views prompted new chemical discussions and became the focus of works by the German/Dutch physician Franciscus Sylvius (1614–1672) and the English physician and anatomist Thomas Willis (1621–1675). For Sylvius, excesses of acid or alkali were the real causes of disease. Diseases resulted not from spiritual seeds, as van Helmont thought, but from the acidic and alkaline natures of specific bodily fluids (e.g. lymph, saliva, pancreatic juice, and bile). Willis is best known for his work in cerebral anatomy and neurology, but in an early work called De fermentatione (1659) he joined discussions about chemical medicine and associated the cause of change in the natural world with fermentation. An English translation was published as A medical-philosophical discourse of fermentation in 1684. Blending Helmontian themes with a corpuscularian, or particulate, view of nature, he understood fermentation and disease as the result of an inner motion of particles. While maintaining a belief in an animal soul, observations of distillation and the dissolution of animal and vegetable bodies led him to claim the existence of chemical-mechanical operations in the body based upon active (spirit, sulphur, salt) and passive (water, earth) principles. By “principles,” however, he intended not something theoretical and abstract, but rather something physical, particles, defined as that “into which physical things are resolved, as it were, into parts lastly sensible [capable of sensation].”

Note: in this period, few if any translations were what we would consider literal translations. English-language texts hyperlinked in this essay serve as related texts that might serve as English examples, rather than indicating actual translations.

Additional Reading

Debus, Allen. The Chemical Philosophy. New York: Dover Publications, 2002; first published 1977.

Debus, Allen. Chemistry and Medical Debate: van Helmont to Boerhaave. New York: Watson Publishing, 2001.

Moran, Bruce T. Distilling Knowedge: Alchemy, Chemistry, and the Scientific Revolution. Harvard: Harvard University Press, 2005.

Moran, Bruce T. Paracelsus: an Alchemical Life. London: Reaktion Books, 2019.

Wear, Andrew. Knowledge and Practice in Early Modern English Medicine 1550–1680. Cambridge: Cambridge University Press, 2000.