Skip Navigation Bar

Higher Education

Horizontal red line

Changing Explanations in Mind-Body Medicine

Class 5: Descartes and Aftermath

Introduction: Mind and body were only partially distinct conceptually before the philosopher Rene Descartes (1596–1650) introduced what many regarded as radically new philosophical ideas. He claimed that mind and body were fundamentally different substances, body being material and passive while mind was immaterial and active. This philosophical position is commonly called “mind-body dualism” or “Cartesian dualism.” For Descartes and his seventeenth century contemporaries, this approach not only posed a fundamental challenge to long-standing beliefs about physical reality and human nature, but also had complicated implications for medicine.

Claims about the impact of Cartesian dualism on medicine are often overstated and oversimplified. Some authors say that it created a dichotomy that severed mind from body and left earlier, more holistic medical ideas in disarray. But there is no evidence that Descartes actually had this effect. His dualism was in reality an “interactionist” dualism, and much of his work was devoted to explaining how mind and body interact with and influence one another. His treatise on Passions of the Soul (1649) was devoted to explaining this in great detail. Descartes defined passion as the mind's perception of a previously occurring set of movements in the blood or other body fluids. Then using a mechanical model of the human organism building on Harvey’s circulation of the blood and breaking sharply with humoralism, Descartes connected each of the basic emotions to specific physiological causes. His philosophical purpose was to emphasize man’s ability to control his passions and live more rationally and ethically because passions were primarily bodily events that could be allowed to crest and crash like waves without necessarily forcing harmful human response. The human mind could exercise its will by waiting out the rising and falling of the emotional waves or by forcing their currents back into more constructive pathways.

Descartes’ philosophical work thus emphasized explicitly that mind and emotion, while separate from the material body, are also closely associated with the body and strongly interactive with it. It was especially important to Descartes that mind can willfully and self-consciously act upon the body. These ideas tended to emphasize will and personality in ways that underscored human psychology as operating in a separate domain from biology rather than being subject to it and determined by it, as in the humoral theory of traditional medicine.

In the century and a half after Descartes, medicine followed three different paths. Those who followed the first path tried to build on Descartes to create systems of medical mechanism or “iatromechanism” in which a mechanically functioning body replaced the humor-dominated body of traditional medical theory. This was represented by physicians like Giorgio Baglivi (1668–1707) and Friedrich Hoffmann (1660–1742), the latter publishing Fundamenta Medicinae (“Fundamentals of Medicine”) in 1695 as a iatromechanical textbook. Those who followed the second path rejected medical mechanism as too theoretical and too far removed from the realities of everyday medicine. They attended to the details of clinical practice and tried to construct “natural histories” of disease as they observed and recorded those histories over time at the patient’s bedside. Thomas Sydenham (1624–1689) in the seventeenth century and William Heberden (1710–1801) in the eighteenth were good representatives of this pathway. The third path was pursued by those who focused on applying anatomical knowledge through postmortem dissection to the retrospective understanding of pathological symptoms. This was generally called “pathoanatomy” and its principal eighteenth century representative was Giovanni Battista Morgagni (1682–1771), author of De Sedibus et Causis Morborum (“On the Seats and Causes of Diseases”) published in 1761.

Those who travelled the first two paths accepted Cartesian dualism as a reality and gave plenty of room in medicine for the psychological influences of mind and emotions on the onset, course, and treatment of disease. Those on the third path either ignored psychological influences and concentrated on biology alone by studying disordered anatomical structures without allowing a role for the influence of the immaterial mind, or they investigated the anatomy of the brain and nervous system in order to make normal and abnormal anatomy the causal foundation of human thought and behavior without resorting to mind-body dualism. Work of this last kind led in the direction of exclusive biological “materialism” and was represented by Julien Offray de La Mettrie’s (1709–1751) L'Homme Machine (“Man Machine,” 1748). Jerome Gaub (1705–1780) countered La Mettrie in his dualistic De Regimine Mentis (“On the Influence of the Mind,” 1763). Gaub’s approach was dominant in the late eighteenth century, but over time LaMettrie’s position gradually came to seem less radical and more mainstream.


  • Descartes, Rene. Philosophical Work. Translated by E.S. Haldane and D.R.T. Ross, Vol. I. New York: Dover, 1955, 331–356.
  • Hoffmann, Friedrich. Fundamenta Medicinae. Translated and Introduced by Lester S. King. London: Macdonald, 1971, 39–47, 55–58, 103–108.
  • Porter, Roy. The Greatest Benefit to Mankind: A Medical History of Humanity. New York: W.W. Norton & Company, 1997, 217–219, 228–231, 246–257, 263–264.
  • Rather, L.J. Mind and Body in Eighteenth Century Medicine: A Study Based on Jerome Gaub's De Regimine Mentis. Berkeley: University of California Press, 1965, 53–56, 70–71, 105–107, 140–142, 173–175.

Discussion Questions

  1. In Passions of the Soul Descartes says that because men have souls and dogs do not, men can exercise much greater control over their emotions because dogs can only react by biological instinct whereas men can impose self-conscious, willful restraint. Descartes writes “[W]hen a dog sees a partridge he is naturally disposed to run towards it … But nevertheless setters are usually so trained that the sight of a partridge causes them to stop … [And] since we can with a little industry change the movement of the brain in animals deprived of reason, it is evident that we can do so yet more in the case of men, and that even those who have the feeblest souls can acquire a very absolute dominion over all their passions …” (p.356)

    How does Descartes’ approach influence our expectation of one’s self control over her or his emotions?
  2. How does focusing on self-awareness and the exercise of will serve to separate the domain of psychology from the domain of biology? Does a strongly biological approach to human behavior and personality as in humoral theory significantly reduce or even eliminate our sense of control and responsibility for our own actions?
  3. Iatromechanical systems like Hoffmann’s represented the first-developed post-humoral medical theories. They also incorporated Harvey’s discovery of blood circulation and Descartes’s mechanical explanation of physiological processes. Yet these “modern” systems also carried over much of traditional medicine, as when Hoffman writes “When humors cannot properly circulate or be discharged through suitable vessels, they stagnate and become corrupt … [and] from this are produced plethora, disproportions … and many resulting diseases. (p. 42) … Sometimes it greatly conduces to health to induce vomiting, to sweat, and to drink good wine a little freely.” (p. 104)

    Given these details of Hoffman’s system, what explains the appeal of iatromechanism to his contemporaries?
  4. Why did physicians like Sydenham and Heberden so vigorously reject theoretical speculations in medicine, especially given the reality that new systems like iatromechanism primarily served as replacements for what by the later seventeenth century was increasingly perceived as “old-fashioned” humoral theory? In what sense could Sydenham and Heberden be said to have revived the tradition of “bedside Hippocratism”?
  5. Postmortem pathoanatomy such as Morgagni’s had the advantage of applying modern anatomical knowledge to medicine in a practical way. What were the limitations of pathoanatomy? Why was the stethoscope (invented around 1800), which allowed physicians to “see” anatomical abnormalities while the patient was still alive, hailed as a great leap forward?
  6. Why were physicians who relied on either iatromechanical systems or close bedside observation more likely to “see” the influence of psychological factors in the course of illness and treatment than physicians who relied heavily on pathoanatomy and only looked silently at and probed biological structures? What role do spoken words play in medicine that is sensitive to patients’ emotional experiences, whether used by patients to convey their feelings to their physicians or by physicians to offer comfort, reassurance, and hope?
Horizontal red line


Illustration of a red quill pen