Tuesday, December 30, 2008

Review of Dominic Murphy: Psychiatry in the Scientific Image

This review is forthcoming in Philosophy in Review, Vol. 28 no. 6.

Dominic Murphy. Psychiatry in the Scientific Image.
Cambridge, MA: MIT Press 2006. Pp. 410.
US$36.00 (cloth ISBN-13: 978-0-262-134355-2).

There are many approaches to understanding mental illness; contemporary psychiatry builds on a medical approach. Murphy defends a particular version of scientific psychiatry, with a focus on how it theorizes mental illness, rather than on how it tries to help people. So his book is about the reality of mental disorders, their explanation, and classification. He explores the definition of mental illness, and discusses what a scientific psychiatric theory should and should not aim to achieve. Murphy ends with an extensive discussion of the objectivity of psychiatric classification. For most topics, he illustrates his points by discussing how they apply to one or more kinds of mental illness. Throughout he gives the reader helpful signposts as to what he has argued so far, what he is about to argue, and how that fits in with the overall structure of the book. This will be especially useful for those readers who are not planning to read the whole work, or who will read different parts at different times. This is a dense, scholarly work of over 400 pages that refers to current work in both psychiatry and philosophy, including philosophy of medicine, philosophy of mind, general philosophy of science, and philosophy of biology. There is a short, very incomplete index.

Murphy argues for a revised view of the medical model of psychiatry, which is not tied strongly to existing mental concepts. Especially since Murphy has been a student of, and co-author with, Stephen Stich, it is illuminating to see traces of eliminativism here. Murphy is quite ready to move on from old concepts when necessary, and does not take the primary task of philosophy to be conceptual analysis. He is thoroughly wedded to a scientific approach to understanding mental illness, and he is especially impressed with the success of the cognitive neurosciences. When our ordinary language or standard practice is in conflict with scientific knowledge, he argues for revising our concepts and practices. Thus, for example, he argues that our standard ways of demarcating mental illness from other illnesses and disorders cannot be rationally justified, and so we should embrace a new, initially counterintuitive understanding of mental illness that would, among other disorders, include at least some forms of blindness. In a related vein, he argues that we should abolish the distinction between psychiatry and clinical neuroscience, because cognitive neuroscience is the best science we have to understand mental illness. However, Murphy is not arguing for an extremely reductionist approach to the mind; rather, he embraces a version of the biopsychosocial model that allows different levels of explanation. At the end of the book, he argues for classification of mental disorders based on causal explanation, as found in much of the rest of medicine, but rejected by the widely used manuals of psychiatric classification. He argues that such an approach is both scientifically preferable and pragmatically more useful.

The book’s ambitious and occasionally perplexing middle section attempts to provide a theory of psychiatric explanation. It draws on philosophical discussion of explanation in cognitive psychology and in biomedicine. In Chapter 5, Murphy explores to what extent factual elements can be isolated to ground psychiatric explanation, and to what extent the explanation of mental disorder requires evaluative assumptions about what is normal or rational. He concludes that in much of psychiatry norms will run through the whole explanatory process, so that the prospects for a mechanistic program of the cognitive neuroscience of mental illness are dim. This causes considerable trouble for the scientific project since there is little prospect of getting intersubjective agreement on epistemic or moral norms. He considers in some detail the cases of delusion, addiction, and psychopathy, and in each case, finds that it is impossible to eliminate norms from the explanation of the phenomenon.

These conclusions seem to entail that Murphy’s earlier confidence in the medical model should be rather diminished. Yet he goes on, in a manner reminiscent of Hume in the case of the missing shade of blue, as if these problems are minor and do not create a problem for the whole project. His attitude seems to be that psychiatric explanation will sometimes be slightly incomplete or patchy, with no possibility of a full account of the mechanisms involved in the production of the phenomena of psychopathology, but that the scientific/medical approach is still the best one available. In Chapter 6, Murphy gives an account of causal psychiatric explanation. He coins the notion of an exemplar, which he describes as the idealized theoretical representation of a disorder — its typical course and symptoms. The explanation works by ‘displaying the causal relations among pathogenic processes that produce the symptoms’ (212). He proceeds to sketch how psychiatric explanation can proceed in some fairly simple cases and then in schizophrenia. In the next chapter, he sets out how social factors can enter into the explanation. In
Chapter 8, Murphy addresses the role of evolutionary theory in psychiatric explanation, arguing that many recent attempts at evolutionary explanation of psychopathology are unsuccessful. His analysis of the failures points to what a successful approach to evolutionary explanation should look like.

Together, the chapters in this middle section give a reasonably detailed picture of how Murphy envisions psychiatric explanation. He carries out a difficult project well: his aim is not to make strong empirical claims about which explanations are more successful, but rather to make a philosophical point about the feasible forms of psychiatric explanation. In the setting out
of his ideas, he addresses many particular controversies and debates in theoretical psychiatry and cognitive science. Owing to the nature of the subject of philosophy of psychiatry, which defies neat categorization and exceptionless generalizations, it is very difficult to arrive at one comprehensive theory or to make straightforward, unequivocal claims. Murphy’s discussion is a case study of how many qualifications and diversions are required by an even moderately thorough approach.

The final two chapters are relatively simple by comparison, because their task is simpler. Murphy covers familiar ground in his criticisms of the classification scheme used by most recent edition of the DSM (the Diagnostic and Statistical Manual of Mental Disorders). His advocacy for the merits of a causal taxonomy is powerful. He acknowledges that the lack of corroborated
theories about the causes of mental disorders will place major limits on to what extent a causal taxonomy can be carried out, but urges that it is still possible to make some progress even in the absence of a fully worked out theory. He gives some indication of how the classification would go using exemplars, and he argues that this would be useful not just for research purposes but also clinically.

Murphy’s book is a landmark achievement in the philosophy of psychiatry. Its claims are often plausible and interesting, and the arguments for them are carefully made. It is certainly the most philosophically sophisticated defense of the medical model of psychiatry that has been made to date. It is a challenging book to grasp as a whole, and there are many places where the argument could be clearer or is vulnerable to criticism, yet it deserves attention from philosophers of science and philosophers of psychology.

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