Adam Hayden reviews Dien Ho’s A Philosopher Goes to the Doctor: A Critical Look at Philosophical Assumptions in Medicine (Routledge: 2019).
Dien Ho is a philosopher who goes to the doctor, in his book with the same name, and wow did that title resonate! I’ve not been shy about my own diagnosis with the aggressive brain cancer, glioblastoma, that I received in 2016, while completing the requirements for my master’s degree in philosophy. Central to Ho’s text is a healthy dose of epistemic humility, the recognition that our beliefs are often on more slippery ground than we’d like to admit.
“The aim of this book,” writes Ho, “is to look at the philosophical concepts at the basis of modern medicine in a way that is accessible to non-philosophers” (2). It is his “grand wish” that this book improves the practice of medicine (ibid). A Philosopher Goes to the Doctor is the latest book in recent years to expand the interest in philosophy of medicine. Other titles include phenomenologist Havi Carel’s (2008) Illness: The Cry of the Fleshand her (2018) Phenomenology of Illness, Jacob Stegenga’s (2018) Care and Cure: An Introduction to Philosophy of Medicine, and philosopher Alex Broadbent’s (2019) Philosophy of Medicine. Though, readers should not take the recent interest as a signal that all has been said on the topic, nor that authors always agree! Ho writes about his book, “The purpose of this book is not to look at modern medicine with deep skepticism” (5), which I don’t think is a stretch to say is at least a tacit rejection of a position dubbed medical nihilism articulated by Stegenga. This is all to situate Ho’s book in the emerging genre.
“One of the main goals of medicine is to improve the health of individuals” (7), Ho begins, and this commonsense statement comports with both his practical approach to the philosophy of medicine and his desire to reach medical researchers and clinicians qua non-philosophers. Medicine, of course, is based on science, and so a summary from the past fifty or sixty years of philosophy of science plays a central role in Ho’s text. In fact, while there is no denying that the content of Ho’s book is indeed philosophical reflections on the practice of medicine, the text itself read to me like a primer on philosophy of science, with examples from medicine to illuminate the philosophical insights, rather than a book about particular medical protocols.
Ho introduces an important philosophical issue early in his text that shapes the chapters to come. “For starters,” Ho writes, “if medicine is science-based, one naturally wonders what exactly makes something a science” (2). He introduces readers to the so-called demarcation problem. It turns out to be pretty tough to draw clear boundaries between science and pseudo-science. In the era of fake news, demarcating science from its competitors is a worthy pursuit.
By way of the demarcation problem, Ho introduces readers to positivism. This 20th century intellectual movement and methodological commitment prized empirical data as the only meaningful content of science because only empirical data can be tested or verified. Ho notes that verificationism quickly meets its limits. Statements like, “All metals expand when heated” (12) cannot be verified because scientists have only finite empirical data, and so a broad, categorical statement wouldn’t pass as science. Surely, if we’re trying to pick out scientific claims, eliminating a statement like that one isn’t the right result.
Ho turns next to discuss induction. According to Ho, “Inductive inferences in medicine are common” (13). Induction is a broad category of reasoning that includes going from a limited sample to a general claim. Ho appeals to the Scottish philosopher David Hume [1711-1776] who raised a fundamental problem with induction: we cannot justify the use of induction, without using induction! We are apt to say something like, induction has always worked for me each time that I’ve used it. Of course, this itself is an inductive argument. Ho explains, “It is like asking your shifty friend if he is lying to you. His declaration ‘Of course not!’ would bring little confidence” (91).
Ho goes on to introduce Karl Popper who proposed an alternative demarcation criterion. Popper’s critique centers around his argument against induction as a scientific method. On Popper’s view, it is not empirical verification that we are after; instead, scientists seek to falsify their predictions. A claim is scientific when it can be falsified by empirical data. If a prediction turns out to be false, then, according to Popper, we can infer that the theory that produced that prediction must be false. This is superior to induction, Popper thinks, because falsification is formulated deductively.
Spoiler alert! Falsificationism falls flat, too, and Ho explains why. Ho introduces two pioneering figures in philosophy of science, Pierre Duhem [1861-1916], an early-20th century French scientist and the American, mid-20th century philosopher, W.V.O. Quine [1908-2000]. Duhem and Quine are each well-known for a position called theory holism. They remind us that a scientific theory is not a single, well-articulated statement or hypothesis, but theories are vast networks of premises and hypotheses, sometimes called a theory complex. “Duhem tells us,” writes Ho, “that when a scientist confronts a false prediction, she has a choice to make: reject the hypothesis in question or reject one or more auxiliary assumptions that are needed to generate the experimental prediction” (142). The problem then is apparent – seeing theories as large complexes of connected statements, we cannot deduce exactly where the falsity lies.
To recap, verificationism undermines confidence in our general claims because our datasets are always finite, and induction risks a perniciously circular justification. Now, we see falsificationism, even with its deductive formulation, faces its share of problems. Next, Ho turns to using explanation as a guide for warranting belief in scientific claims. In his practical and commonsense style, Ho asserts, “Explanations intuitively provide more information than knowledge alone” (67). And with this, Ho lands on Inference to the Best Explanation (IBE), a form of reasoning called abduction. Ho defines IBE as “inferring the truth of a hypothesis on the basis of its explanatory power” (69). The idea is that scientists formulate many hypotheses to explain the available evidence they gather, and from these hypotheses, some explain the evidence better than others. The hypothesis that offers the best explanation of the evidence is likely true, or close to it.
Ho asks, “Can we make research progress, diagnose, and treat adequately if we do not know the explanations of ailments and disabilities? And, if we can, why should medicine worry about explanations” (85)? Here, I think an earlier comment from Ho is informative: “When it comes to medical research and clinical practice, we want to not merely get it right; we want to get it right for the right reason” (45; my emphasis). Here, the right reasons are having to do with finding an epistemic foundation, “they elevate mere guesses to something better, such as justified beliefs” (ibid). Motivating our pursuit of getting it right, requires that we understand the mechanisms of action; that we explain why a therapeutic, or some other intervention works, and connecting the dots in Ho’s text in this way is helpful. Indeed, in the first sentence of the book, Ho writes, “Modern medicine is great because it works and it is based on science” (2; my emphasis).
Ho raises three problems with IBE. First, “The ‘best of the bad lot’ objection points to the fact that IBE claims that we ought to accept a hypothesis because it is the best explanation for the evidence. But ‘best’ is a comparative evaluation” (74). If an investigator is choosing the best explanation, there is nothing to guarantee that the true explanation lay within the set of hypotheses. A second problem with IBE is that “finite amount of evidence can never single out one explanation as the only explanation” (ibid). We say that the best explanation is underdetermined by the evidence. Ho’s manuscript predates the global SARS-CoV-2 pandemic, but that example may illuminate the trouble here. The symptoms of the novel coronavirus share similarities with the flu. If a clinician has only a finite set of symptom presentation data from which to diagnose a patient, whether infection with the novel coronavirus or influenza best explains the symptoms is underdetermined.
The third problem that Ho raises for IBE involves the historical record of past science: “Finally, the history of science has shown us that false theories can be extremely good at providing plausible explanations” (76). Plenty of past theories have been successful, yet false. For an example, Ho offers phlogiston theory, a theory that posited a combustible substance, phlogiston, that materials release when combusted. Phlogiston theory was ultimately superseded by oxygen theory, yet phlogiston was explanatorily very successful. “As we now know, phlogiston does not exist; yet, as a dominant theory in chemistry, it did a wonderful job of explaining various experimental observations” (ibid).
In the end, the practical utility of using explanation to drive our acceptance of scientific theories leaves Ho with an optimistic outlook for modern medicine. It’s Ho’s pragmatism that enables him to bracket some of the thornier epistemic concerns with explanation as a rule for belief justification. In his words, “A philosophically informed medicine is one that is tolerant, open-minded, transparent, and humble. These traits stem not from some vague commitment to political virtues; instead, they come from understanding the limits of what we can know” (149).
Ho’s analysis of concepts like health and disease, while complete, does not diverge from other accounts in the discipline. He also spends time contrasting frequentism and Bayesianism in statistics, an important topic, but likewise, well-covered. He discusses Helen Longino’s social epistemology as an analysis of scientific practice that advocates for an open and transparent science. However, I have elected to focus on what I think makes Ho’s text distinct: his thorough engagement with philosophy of science, canvassing the 20th century, and doing so with an eye for accessibility. Ho writes an exceedingly clear text that provides non-philosophers a terrific entry point to explore the philosophical assumptions underpinning medicine. Overall, this book is a welcome addition to the growing corpus of philosophy of medicine literature.
Adam Hayden, MA is a writer, speaker, and organizer. He is a research assistant for the Department of Philosophy at Indiana University, Indianapolis. Follow Adam on Twitter @adamhayden and find his personal blog, www.glioblastology.com.