Theory and Experiment Redefine Medical Practice and Philosophy

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Theory and Experiment Redefine Medical Practice and Philosophy


In the sixteenth and seventeenth centuries there was considerable debate among physicians about the appropriate philosophical basis for their art. The humoral theory of Galen and Avicenna remained influential while the iatrochemists advocated a more aggressive application of new chemical remedies. Drawing on Descartes, Galileo, Newton, and Harvey, the iatromechanist school began to think of the human body as a machine. In contrast, the early vitalists believed in a vital force that differentiated living matter from nonliving. The boundaries between the different systems were not rigid. The majority of medical practitioners, not holding university degrees, relied more on first-hand experience and traditional medical knowledge than on a philosophical framework.


With the appearance of universities and their faculties of medicine in the twelfth through fourteenth centuries, physicians educated at universities became eager to distinguish themselves from other medical practitioners, who they disparagingly described as "empirics." The traditional medical curriculum was devoted to the study of the works of the Greek medical writer Galen (c. a.d. 130-c. 200), and of the great Persian physician Abu-Ali Al-Husain Ibn Abdulla Ibn Sina (c. 980-1037), known in the Western world by the Latinized name Avicenna, who extended Galen's system.

Galen based his medical system on the theory of four humors, which like the theory of four elements originated in the teaching of the Greek philosopher Empedocles (490-c. 430 b.c.) and had been embraced by the philosopher Aristotle. In the Galenic view, health resulted from the balance between blood, phlegm, yellow bile, and black bile. Disease was a matter of internal imbalance, which could be restored through diet or through purgation or bleeding.

By the sixteenth century medical scholars had joined in the controversy between "ancients" and "moderns" that also affected the study of literature and theology. While some scholars sought to restore the teachings of the ancient writers in their original purity, others felt that too much respect had been paid to the teachers of antiquity. In scientific areas there was a new emphasis on experiment and observation as well as new theories of health and healing. For physicians the need for new approaches was also seen as necessary to deal with new diseases, particularly syphilis, which made its first appearance in Europe after the return of Christopher Columbus (1451-1506) from the New World.

The alternative system known as iatrochemistry is usually considered the creation of the controversial Swiss physician Theophrastus Bombast von Hohenheim (1493-1541), generally known by the name he adopted, Paracelsus. Scholars agree that Paracelsus traveled widely and sought knowledge from alchemists, barber-surgeons, midwives, and miners. They disagree as to the extent of his study at universities. There is evidence he received a doctoral degree at Ferrara in Italy. In his practice of medicine he was credited with a number of nearly miraculous cures, and in 1526 he was appointed town physician in Basel, Switzerland, where he publicly burned the books of Galen as a protest against the traditional teachings. His supporters called him, among other things, the Luther of the Physicians, seeing in him a needed reformer. His opponents were in the majority, however, and had him run out of town.

As alchemists, Paracelsus and his followers wanted to replace the four elements of Empedocles, and the corresponding system of four humors, by a set of three fundamental "principles": salt, sulfur, and mercury. This proposal grew out of alchemical experimentation, which increasingly involved the application of heat to separate materials into their volatile part (mercury), fluid part (sulfur), and solid remainder (salt). More important than this new theory, perhaps, was the Paracelsans' insistence that the proper purpose of chemistry was not the changing of base metals into gold but the creation of medicines. Paracelsus gained some followers among the empirics but loved controversy too much to be accepted by the majority of university-educated physicians. His followers frequently gained support from royal families. In France the King supported Paracelsan physicians against the medical faculty at Paris, which remained faithful to Galen.

New discoveries in the physical sciences stimulated an alternative school, based more on physics than chemistry, known as iatromechanism, or sometimes iatromathematics. The Italian mathematician and physiologist Giovanni Alfonso Borelli (1608-1679), a friend of Galileo (1564-1642), is generally considered the founder of this school. In his book De Motu Animalum, published shortly after his death, he describes the skeletal system of various animals as a system of mechanical levers controlled by the muscles. Iatromechanists were quick to seize on the idea of the English physician William Harvey (1578-1673) that the heart acts as a mechanical pump. They also claimed the great French philosopher René Descartes (1596-1650) as one of their number. While Descartes is known primarily for his contributions to philosophy and mathematics, he wrote also on physics and, living near the butcher's quarter in Amsterdam, conducted many dissections of animals. Descartes concluded that animals were in essence machines while humans were a combination of mechanism and a nonmaterial mind. The success of the British mathematician Sir Isaac Newton (1642-1727) in providing a mathematical framework for physics through his three laws of motion also served to strengthen the iatromechanist school.

Vitalism is the belief that living organisms possess qualities that are not present in inorganic matter. The vitalist approach to medicine appears in the work of the Flemish physician and alchemist Jan Baptista van Helmont (c. 1750-1644), a follower of Paracelsus. Van Helmont and his followers believed that only living organisms could produce the "ferments" that permitted the digesting of foodstuffs and their incorporation into the organism, and thus that the chemistry of living or once-living matter was forever separated from that of inanimate matter.


The increased emphasis on observation and experiment in the seventeenth century would change the way in which university-educated physicians viewed their calling. In 1600 such physicians considered themselves to be students of nature. Many, including William Gilbert (1544-1603), physician to Queen Elizabeth I, engaged in physical experiments. "Physic," from the Greek word meaning nature, was understood to include recommending good diet and other health practices as well as trying to cure the sick. By 1700 the physician was mainly concerned with treating the sick, and clinical experience gradually replaced much of the traditional philosophical training.

Each of the major medical theories current in the seventeenth century continued to influence the practice of medicine up to the nineteenth century and to some extent even the twentieth. Blood-letting, and the application of medicinal leeches, continued through most of the nineteenth century. While a young ship's surgeon, Julius Mayer (1814-1878) made the observation that sailors bled in the tropics showed less use of oxygen than people in temperate climates. These observations were the catalyst that led him to formulate the law of energy conservation. Notions of restoring the equilibrium of the patient may have played a role in the experimentation with "antagonist therapies" in the 1920s, such as the deliberate infection of patients with malaria to treat advanced syphilis.

Iatrochemistry might claim credit for the expansion of chemical therapies. A flurry of new chemical therapies followed the late-nineteenth-century discovery of dyes that could stain, and thus attach themselves to, specific tissues. The influence of iatrochemical theory on the diet of Europeans was also profound. The diet of the wealthy, the only people who could afford a variety of foods, in 1600 emphasized heavy use of sugar, cooked vegetables, and warmed wine, all of which were expected to insure the balance of the Galenic humors. A hundred years later there had been a shift to fresh vegetables or salad, minimal use of sugar, and cold beverages, much as in modern practice, justified by the three Paracelsan principles and the idea of digestion as fermentation.

The iatromechanist tradition has continued also, perhaps with the least fundamental change. The diagnosing physician's reliance on blood pressure, temperature, and timing the pulse to assess the state of health of the patient has not changed in principle since the seventeenth century.

Vitalism has had a more checkered career. Vitalists are behind the original separation of chemistry into organic and inorganic categories. The debate about the spontaneous generation of organisms from nonliving matter appeared to be finally resolved by the demonstration in 1860 by the French chemist Louis Pasteur (1822-1895) that meat broth can be preserved indefinitely if microbes are excluded, an apparent victory for vitalism. In 1828, however, the German chemist Friedrich Wöhler (1800-1882) demonstrated that urea, a simple compound found in animal waste, can be made in the laboratory from ammonium cyanate, considered to be an inorganic compound. In modern science, the vitalist position is no longer accepted, at least outside the area of mental phenomena, and the difference between living organisms and nonliving is considered to be a matter of vastly greater complexity, much of it to be found in the molecular structure of enzymes, the modern counterpart of van Helmont's ferments.

Assessments of Paracelsus have varied through the centuries. He has been considered something of a Swiss national hero. The young romantic poet Robert Browning wrote a play in verse about him in 1835. The Swiss psychoanalyst Carl Gustav Jung (1875-1961) wrote two essays, "Paracelsus the Physician" and "Paracelsus as a Spiritual Phenomenon," praising the controversial physician as an innovator in medicine. His collected works have been published, and several scholarly papers about his role in the evolution of modern medicine appear each year.


Further Reading


Cumston, Charles Greene. An Introduction to the History of Medicine. London: Dawsons of Pall Mall, 1968.

King, Lester S. The Philosophy of Medicine. The Early Eighteenth Century. Cambridge, MA: Harvard University Press, 1978.

Porter, Roy. The Greatest Benefit to Mankind: A Medical History of Humanity. New York: Norton, 1997.


Cook, Harold J. "The New Philosophy and Medicine in Seventeenth-Century England." In D. C. Lindberg and R. S. Westman, eds., Reappraisals of the Scientific Revolution. New York: Cambridge University Press, 1990.

Laudan, Rachel. "Birth of the Modern Diet." Scientific American 283 (August 2000): 76-81.

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Theory and Experiment Redefine Medical Practice and Philosophy

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