Rationalism and Empiricism in Modern Medicine
Newton, Warren, Law and Contemporary Problems
WARREN NEWTON [*]
About ten years ago, after fellowships and clinical experience in a community setting, I had my first experience as a ward attending in a university hospital.  We were working with cardiac patients, and I was struck by the common treatment each patient received. No matter what the symptoms, patients received an exercise treadmill, an echocardiogram, and were put on a calcium channel blocker.  This was remarkable at the time because there were in excess of thirty randomized controlled trials showing the benefit of beta-blockers, a different class of medicines, to treat patients following a heart attack. Indeed, by 1990, there was initial evidence that calcium channel blockers not only failed to improve outcomes, but actually made them worse.
The point is not to criticize the medical culture at that hospital--similar examples can be found at every medical center--but rather to explore why there was so much fondness for calcium channel blockers. One factor was the substantial drug company support of faculty research on silent myocardial ischemia. Another factor was what might be called medical fashion. The most likely explanation, however, was more fundamental. For my cardiology colleagues, it was biologically plausible that calcium channel blockers were better than betablockers. Like beta-blockers, calcium channel blockers reduce heart rate and myocardial wall stress, but they lack the side effects of beta-blockers. In other words, what was important to my colleagues was not the outcome of the critical trials, but our understanding of the mechanisms of disease.
This is an example of the tension between rationalism and empiricism in medicine. Rationalism is the search for and emphasis on basic mechanisms of disease, which then color all clinical decisions. Empiricism is defined as the emphasis on the outcomes of individual patients and groups of patients. My thesis is that there is an ongoing and fundamental tension between these two different ways of thinking. While these ways of thinking can be complementary, the tension persists, exploding around specific clinical and legal controversies. Understanding the tension between rationalism and empiricism provides important background in considering the role of expert advice.
Part II of this article explores the roots of rationalism and empiricism in the Hippocratic tradition. Using the Flexner report as a text, Part III emphasizes the triumph of the rationalists in the founding of modern medicine. Part IV briefly describes the development of clinical epidemiology and the evidence-based medicine over the last thirty years. Part VI attempts to explicate how this tension illuminates fundamental clinical and policy questions that doctors, the health care system, and the legal system confront today. My goal is not to present a detailed explication of the epistemology of medical science, but rather an intellectual history  sketching out what has animated the thinking of clinicians.
The Hippocratic tradition rests on many authors, not just the historical Hippocrates of Cos, but a plethora of later writers through antiquity, from Greece to Alexandria to Rome. This article focuses on two major sects of that tradition that dominated in Alexandria from the fourth century B.C. through Roman times.  The dominant medical influence in the classical age was rationalism. Tracing its origin from Thessalos and Drakan, the sons of Hippocrates, rationalism is the oldest of the sects. Thessalos and Drakans emphasized the importance of natural philosophy in medicine, believing that "where observation failed, reason might surprise."  The fundamental theory was the doctrine of "humours" as first taught by Pythagoras:
The body of man has in itself blood, phlegm, yellow bile, and black bile:... [N]ow he enjoys the most perfect health when those elements are duly proportioned to one another in respect of compounding power and bulk and when they are perfectly mingled. …