John Locke
John Locke
  • Bacon, Locke, and Newton—I consider them the three greatest men who have ever lived, without any exception.
  • —Thomas Jefferson, 1789
Many people forget that John Locke was a physician, and many who know that he was a physician presume that his life-long practice of medicine exerted very little influence over his work as a philosopher. In fact, however, there is good reason to think that Locke’s philosophical views were deeply shaped by the practice of medicine. Caring for patients enhanced his respect for the prerogatives of individuals, tempered his trust in the judgments of experts, including government officials, concerning what is best for others, and engrained in him a deeply empirical approach to human knowing and its limitations that pays more attention to real-world results than to theoretical predictions. His writings both draw on his medical practice and offer deep insights on contemporary medicine and biomedical science.

In the breadth and depth of his impact on those who came after him, Locke is one of the most influential physicians who ever lived, though his contributions are not contained in medical textbooks. A deep thinker of the Enlightenment, Locke also stands today as one of the founders of economic and political liberalism, a leading light of the philosophical school of empiricism, one of the greatest contributors to the field of epistemology, and probably the single thinker who exerted more influence over the American founders than any other. Essential concepts of contemporary political discourse including freedom, natural rights, representative government, and the right of revolution have all been powerfully shaped by his writings.

Locke’s Life

Locke was born in Somerset, England. His father was an attorney, and both his parents were Puritans, meaning he grew up in a nonconformist home. He studied at Westminster School in London and then attended Oxford University. Finding the curriculum less than engaging, much of his education was self-directed. He earned bachelor’s and master’s degrees in his 20s, working with great scientists of the day including Robert Boyle, the chemist who described the relationship between gaseous pressure and volume, and Robert Hooke, one of the first scientists to study microorganisms and the person who coined the term “cell” to denote the basic unit of life.

While at Oxford, Locke met and befriended the man who would become the Earl of Shaftesbury. Attracted to the study of medicine, Locke earned the older man’s trust and moved to London to become a member of his household. Although he would not earn his medical degree until his 40s, Locke continued his medical studies with Thomas Sydenham, “the English Hippocrates,” whose empirical approach to medicine emphasized detailed patient observation and record keeping. Later, Locke persuaded Shaftesbury to undergo surgical drainage of what was likely a hepatic abscess—a radical procedure for the day—which proved successful and may have saved his patron’s life.

In 1672, Shaftesbury was appointed Lord Chancellor, exerting great influence over not only British politics but also Locke’s political understanding. Unfortunately, Shaftesbury’s political fortunes soon foundered, leading Locke to leave for France. As the situation improved, Locke moved back to England, but in 1683 the Rye House Plot to assassinate King Charles II and his brother James was discovered. Although there is no evidence Locke was involved, he was a member of the Whig party, which opposed absolute monarchy and advocated for a parliamentary system. Locke judged it best to flee the country again, this time for the Netherlands, where he remained for more than six years.

Human Understanding

Within a year of Locke’s return in 1689, he published four great philosophical and political works: the Essay Concerning Human Understanding, Part 1 and Part 2, the Letter Concerning Toleration, and his First and Second Treatises of Government. These writings reveal that he is much more of a forerunner to Adam Smith, Friedrich Hayek, and the “knowledge problem” than many commonly suppose. The first, heavily influenced by Sydenham, argues that the human mind at birth is a blank slate, upon which experience writes all our knowledge. Locke denies the widely held belief in innate ideas, such as the existence of God and mathematical and moral truths. He argues that our sense of personal identity is grounded in continuity of experience. Above all, he argues that the human capacity to know is limited, requiring us to guard against allowing misunderstandings to lead to errors in practice.

Locke is first and foremost an opponent of intellectual pride, the refusal to acknowledge that we do not know everything, that others may have something to teach us, and that everyone still has more to learn. As a physician, he never reached a point at which he believed he had seen everything there is to see, or that he had arrived at a theory of medicine that could reign untouched for all time. Like his teacher, Sydenham, he held that the human organism, health, and disease are so rich and complex that no physician could ever completely encompass them. We can advance in knowledge, but we will always have a long way to go. Writes Locke,

  • There is not so contemptible a plant or animal, that does not confound the most enlarged understanding…. The workmanship of the all-wise and powerful God, in the great fabric of the universe, and every part thereof, farther exceeds the capacity and comprehension of the most inquisitive and intelligent man, than the best contrivance of the most ingenious man does the conceptions of the most ignorant rational creatures. (An Essay Concerning Human Understanding, Book III, Chapter VI)

Locke was, in the best sense of the term, a skeptic. He believed that observable phenomena should always take precedence over theoretical systems. A physician’s theory might dictate that a patient should get better under a particular treatment regimen, but what matters most is not the theory but the patient, and if one approach does not work in practice, physicians should be prepared to consider another. What matters most, and in a sense what is most real, is not the knowledge in textbooks or journal articles, but the particular patient at hand, and all the physician’s labors should always be directed at serving the best interests of the patient.

On Toleration

In the Letter Concerning Toleration, Locke argues that open-mindedness for religiously divergent points of view is a Christian virtue and that states should not concern themselves with the spiritual interests of their subjects, thus helping to establish a principle of separation of church and state. The limitations of the human intellect imply that no person or state can claim to know with certainty the one true religion, meaning that the rights of others to see religious matters differently should be respected. However, Locke’s toleration did not extend so far as atheism, which he derided as denying the very foundation of moral and political life.

Locke’s reservations about compelling any form of religious belief bear implications for science and medicine. To regard our own way as the one and only true way is to convict ourselves of hubris, whether religious, medical, or intellectual, and thereby to cut ourselves off from the possibility of further learning. Others necessarily see things from different vantage points, and it is always possible that their perspectives permit observations that we have missed. The mind of the person of faith, like that of the physician and scientist, should always be prepared to consider new possibilities. Truths are most likely found not in unassailable dogmas but in the restless quest for new knowledge.

“Locke’s great virtue was not certainty but curiosity, a continuous striving to understand that never ceases to examine its own assumptions and seek out new opportunities for learning.”

Locke’s great virtue was not certainty but curiosity, a continuous striving to understand that never ceases to examine its own assumptions and seek out new opportunities for learning. The practice of medicine is not the application of certain knowledge to the cases of individual patients. To the contrary, it is best conceptualized as an unfolding adventure, in which new discoveries remain both possible and necessary in the enhancement of patient care. The senior physician has more experience to draw upon than the neophyte, but in comparison to a “God’s-eye” understanding of medicine, both are at a very early stage in the expedition. In all such cases, dogmatism must be avoided. Locke writes,

  • He that in physick shall lay down fundamental maxims and from thence drawing consequence and raising dispute shall reduce it into the regular form of a science has indeed done something to enlarge the art of talking and perhaps laid a foundation for endless disputes, but if he hopes to bring men by such a system to the knowledge of the infirmities of men’s bodies, he is [much mistaken].

Locke would regard with sympathy the view that patients can have whatever and as many diseases as they want, meaning that medical preconceptions should never blind physicians to the reality of each patient. Occam’s razor—the idea that the simplest explanations are to be preferred—may make a great deal of sense theoretically, but the mind of man is an imperfect instrument, and what to its lights seems preferable does not necessarily correspond to the way things really are. Unlike mathematics, where truths can be deduced from definitions, axioms, and theories, medicine and natural science address realms of inquiry where empirical approaches must always be preferred.

As opposed to closed-mindedness, toleration is an effective strategy in advancing knowledge. By avoiding dogmatism and censorship, each inquirer is more likely to encounter diverse perspectives, and this lively interchange of ideas creates an environment in which knowledge is most likely to be advanced. So long as faith, ideas, science, and medicine remain uncontested and static, no improvement is possible, but the exchange of different perspectives allows both sides to see the matter anew, and thereby stimulates new discoveries. Locke would likely regard with enthusiasm multidisciplinary conferences, journal articles, and professional meetings that foster such lively interchange.

First Treatise: Against Oppression

Locke’s greatest contributions to political philosophy are found in the First and Second Treatises of Government. The First Treatise attacks Robert Filmer‘s Patriarcha (1680), which defends hereditary and absolute monarchy on the grounds that, in the Genesis account, God gave Adam and his descendants unlimited power over other persons and all of creation. Locke contends that Adam did not have absolute authority over his children, authority should not be transmitted hereditarily, and no person has a right to make slaves of others. Besides, asks Locke, who today could legitimately claim to be the heir of Adam—at least more so than anyone else?

At first glance, it might seem that monarchical government plays little or no role in contemporary medicine and natural science. After all, there are no kings or queens, and most medical schools, universities, hospitals, and health systems undergo frequent transitions in leadership. No one claims a right to a job as dean, president, or board chair because of the circumstances of their birth, and it is a rare exception when a leadership post transfers directly to the offspring of a previous incumbent. Yet Locke’s critique of absolute authority is not so irrelevant to contemporary circumstances as it might appear, and his reflections on the point merit careful consideration.

Locke is nothing if not an ardent opponent of oppression, especially the suppression of ideas. He believes that the love of truth must supersede all other loyalties, and that all other virtues arise from it. Physicians and scientists should be ardent defenders of the truth, even when such defense places them at odds with institutions to which they are beholden. A medical school may wish to save face, a hospital may wish to limit its legal liability, and a health system may wish to press its competitive advantage, but from Locke’s point of view, the physician must put truth first, even when doing so has the potential to damage the physician’s career prospects. The rights of conscience must not be abridged. Writes Locke,

  • The imagination is always restless and suggests a variety of thoughts, and the will, reason being laid aside, is ready for every extravagant project; and in this state, he that goes farthest out of the way, is thought fittest to lead, and is sure of most followers: And when fashion hath once established, what folly or craft began, custom makes it sacred, and it will be thought impudence or madness, to contradict or question it.

The suppression and distortion of ideas, as well as all offenses against the best interests of patients, should be resolutely called out. The conscience of the profession of medicine and the healthcare industry resides not in the policy and procedure manuals of universities and health systems but in the hearts of every physician and scientist, and it is the calling of professionals to speak out in such matters. To be a professional is to profess something, to be willing to say what needs to said and do what needs to be done in the service of such higher goods. To preserve such prerogatives requires constant vigilance, lest institutional and cultural pressures erode them.

Second Treatise: In Praise of Freedom

The Second Treatise is one of the greatest works in the history of political philosophy. Following Thomas Hobbes, Locke invokes the idea of a state of nature, but his state of nature is not a state of war of each against all but one of relative peace and comfort, in which people own property and stand in equality to one another. When they agree to be governed, they do so to protect their pre-existing rights of life, liberty, and property, which they retain. So long as governments protect these rights, they retain their legitimacy. Should they threaten them, though, they become tyrants, and the people have the right to rebel. Governments, Locke held, exist for the benefit of the people, not those who govern.

The relevance of Locke’s Second Treatise to contemporary medicine and biomedical science can hardly be exaggerated. The last few decades have witnessed a sea change in the profession of medicine, in which a declining number of physicians hold an ownership interest in their practices and more and more are employed by large group practices, hospitals and health systems, and even investor-owned corporations. As such, an increasing percentage of physicians find themselves under pressure to serve the interests of their employer and those, including federal and state governments, who pay for their work, instead of the interests of their patients.

Consider, for example, physicians who judge it in their patient’s best interest to seek consultation or refer a patient to a colleague or institution outside their own. From the point of view of a physician employer, such a decision might appear a form of “leakage,” sending a potential revenue source to a competitor, and the institution might attempt to enforce rules against it. Or physicians might press for a diagnostic test or form of therapy for which the employer will not be able to collect payment, thus undermining its bottom line. Under pressure from their institutions to relent, how should physicians in such a situation respond?

Extrapolating from Locke, such institutions are founded not for their own benefit but to promote the good of patients. Those who think that diseases and injuries and the patients who suffer them exist to provide revenue to medical practices, hospitals, and health systems have things backwards. In fact, such institutions exist to serve patients. And in most cases, it is the physician and other health professionals caring for the patient face to face, who therefore know the patient best, who are best equipped to make judgments about what best serves the patient. To uphold their professional responsibility, physicians must resist the impulse to allow economic expediency to trump the patient’s good.

Likewise, contemporary biomedical science could glean important lessons from Locke. Ostensibly, contemporary scientific journals encourage freedom of thought and debate, welcoming new and divergent points of view, so long as they are supported by reasoned argument and empirical evidence. In fact, however, many such journals enforce an oft unspoken orthodoxy, ruthlessly suppressing economic, political, and philosophical perspectives that do not conform. Consider, for example, the COVID-19 pandemic, when thoughtful critics who raised prescient questions about the effectiveness of lockdowns, stay-at-home orders, and masking were in many cases cancelled without a hearing.

Writes Locke, “The end of law is not to abolish or restrain, but to preserve and enlarge freedom.” Applied to medicine, this would mean that the proper purpose of physicians joining together in groups and perhaps selling their services to medical practices and hospitals is not to render them easier to control, but so that they have even wider latitude to do what they know needs to be done in the interests of their patients. Likewise, journals of biomedical science should welcome more diverse points of view and reasoned opposition to widely accepted perspectives, an approach much more likely to stimulate scientific discovery than the enforcement of any rigid orthodoxy.

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Practicing medicine convinced Locke of the importance of serving higher purposes—the protection of the liberty, natural rights, and dignity of each human being. From patients he learned that each human person represents a far more rich and complex reality than the human mind can fully grasp. This led him to doubt that any person in authority can safely presume to know what is best for others, to argue that governments exist to serve the people and not the reverse, and to declare that when institutions grow so large and powerful that they threaten the flourishing of individuals, they may and should be replaced. Locke’s insights apply not only to civil governments but also to medicine and biomedical science themselves, which sometimes pose their own threats to the pursuit of truth and human flourishing.

*Richard Gunderman is Chancellor’s Professor of Radiology, Pediatrics, Medical Education, Philosophy, Liberal Arts, Philanthropy, and Medical Humanities and Health Studies at Indiana University. He is also John A Campbell Professor of Radiology and in 2019-21 serves as Bicentennial Professor. He received his AB Summa Cum Laude from Wabash College; MD and PhD (Committee on Social Thought) with honors from the University of Chicago; and MPH from Indiana University.