Is mind–body dualism compatible with modern psychiatry?

Summary

Mind–body dualism is often considered to be incompatible with modern psychiatry for two reasons. First, it is claimed that dualism is falsified by recent advances in neuroscience. Second, dualism is thought to lead to an unhelpful attitude towards patients and their illnesses. I reflect on and challenge both lines of thought and argue that there is no inherent conflict between dualism and psychiatry.

Sometimes it is valuable to examine one's philosophical commitments and consider how these might interact with the day-to-day practical task of psychiatry. In this brief reflection, I want to consider a particular position in the philosophy of mind. Substance dualism (hereafter, simply dualism) is the view that human persons consist of two parts – immaterial (mind) and material (body/brain). Its origin in modern thought is typically credited to René Descartes (1596–1650). It is an unpopular view today, but one that is, in my opinion, often dismissed out of hand before due consideration has been given to it.

In considering the relationship between dualism and psychiatry, I suggest that psychiatrists often believe the two to be incompatible on the basis of two lines of thought. Both are present in a recent article in this journal by Andrew Novick and David Ross, in which they claim that psychiatry is ‘haunted by Descartes’ ghost’ (Novick 2020). I will outline both kinds of objection to dualism and argue that they should be treated with caution.

Dualism and modern neuroscience

First, it is often claimed that dualism is archaic, unscientific and ultimately untenable in light of advances in modern neuroscience. Novick & Ross, for example, portray dualism as a relic of the 17th century, in contrast to ‘more modern perspectives on the [mind–body] problem’ (Novick 2020). They suggest that neuroscience is ‘increasingly providing the crucial data […] to demonstrate the nuanced ways in which bio-, psycho- and social processes are all mediated through the brain’. This statement seems to be an implicit endorsement of some form of materialism, which is, roughly, the view that people consist of nothing but physical matter and that mental states are ultimately reducible and identical to physical (brain) states.

Now, the portrayal of dualism as an outdated, obsolete view is simply misleading. Although its origin may be found in Descartes, its defence continues into the modern day. It was defended by Nobel Prize-winning neurophysiologist John C. Eccles (Popper 1977) and has enjoyed something of a renaissance in contemporary philosophy of mind (Loose 2018). Among other reasons, such thinkers believe dualism to be necessary for making sense of the first-person, subjective quality of mental life – a prerequisite, one might argue, of psychiatric practice.

But what of the claim that dualism is falsified by neuroscience? Neuroscientists have mapped, to an astonishing degree of precision, the many and varied ways in which mental states correlate with goings-on in the brain. It is often thought that this fact gives reason to reject the idea of an immaterial mind. However, it is a mistake to think that scientific findings are decisive in answering philosophical questions. To see this, we must note a further point about dualism that often goes unacknowledged: while it is true that mind and brain are distinct substances, this does not mean that they are disconnected or unrelated. Rather, most proponents of dualism hold that mind and brain causally interact in a dynamic, bidirectional manner. Mental activity brings about changes in the brain leading to volitional behaviour, and changes in the brain cause sensations such as pain to be experienced in the mind (Swinburne 2013). Once this is understood, it becomes clear that dualism and materialism are empirically equivalent theories about human nature. This means that both views are consistent with the same set of empirical data, such that an appeal to such data cannot be made to falsify one theory without begging the question in favour of the other (Moreland 2018). It follows that dualism is not at all inconsistent with the results of neuroscience demonstrating that mental states depend in a fine-grained manner on brain states.

The point is not that dualism is true necessarily, but simply that it is not refuted by a scientific understanding of the brain. There are, of course, philosophical problems that dualism must overcome, and that some consider insurmountable. For example, there is the question of how an immaterial substance could interact with the material world, governed as it is by physical laws. And perhaps one might choose to reject dualism on such grounds. But my claim is that psychiatrists, qua physicians whose expertise is in the workings of the brain, need not necessarily do so. In this arena, physicians must give way to metaphysicians and recognise that there is no inherent conflict between dualism and psychiatry.

Nor is the point to disregard the importance of neuroscience. Our ever-increasing understanding of the detailed physical correlates of abnormal mental states has enabled us to develop effective (physical) treatments to intervene in such processes to the benefit of our patients. In brief, neuroscience is important for the practical task of psychiatry but has much less to tell us about human ontology than Novick & Ross suppose.

Dualism, mental illness and clinician empathy

The above considerations should not be dismissed as merely academic or philosophical, for the first reason for thinking dualism to be incompatible with psychiatry is often used in support of a second. It is sometimes claimed that dualism leads to an unhelpful view of human nature which impedes the psychiatrist's task of treating patients. The point is often made in two parts. First, it is thought that rejecting dualism will help psychiatrists better see that patients' difficult behaviours are really part of a disease process. Novick & Ross, for example, invite us to consider the case of an intravenous heroin user who is known for verbal outbursts, a tendency to discharge himself from hospital against medical advice, and complaints of symptoms that lack an identifiable organic source. They suggest that ‘incorporating neuroscience into the formulation allows [this patient's] clinicians to appreciate that his illness is a medical condition that is within their scope of practice’ (Novick 2020). Second, by viewing a patient's ‘difficult’ behaviour as part of their illness, clinicians will have greater empathy for such patients. This criticism, therefore, does not concern the truth of dualism in relation to psychiatry, but rather its utility.

I have already argued that we need not reject dualism to embrace what neuroscience has to offer in understanding a person's mental life. However, something more needs to be said about this particular objection. It is not at all clear why merely recognising the mediating role of brain states in the production of mental states and behaviours is sufficient to warrant the belief that the latter are components of disease. Neuroscience can tell us how a disease works. It does not tell us that something is a disease. Note that this point applies equally to physical disease as well as mental illness. It would clearly be a misstep to suggest that a having a particular hair colour was a disease simply because we could offer a physical account (for example, in terms of genetics) of how it arose. This shows that demonstrating something to be a disease (physical or mental) involves more than giving a physical description of how it arises. A disease is something we disvalue. Cancer is a disease, for example, because it reduces life expectancy and quality of life, and the same is true of mental illnesses.

Consider the consequences if this were not so. If it were the case that physical accounts were sufficient for defining a disease, this would allow us to pathologise any behaviour that we consider difficult. For, surely all mental states and behaviours – not just emotional dysregulation and addictive behaviours, but also one's political views, sexual orientation, and love or hate of Marmite – are associated with some mediating process in the brain. There is, after all, no other candidate organ from which such things could arise. If all that is required for some behaviour to be counted as pathological is that it is ‘mediated in the brain’, then one must explain why any and every behaviour should not be regarded as a manifestation of disease, since all behaviours are plausibly mediated in the brain. Would anything stop us from medicalising a host of brain-mediated behaviours simply because we do not like them? Mental pathology cannot be reduced to brain states, lest all brain states are reduced to pathology.

Finally, dualism may in fact have greater resources for fostering empathy in clinicians for their patients. Although both dualism and materialism allow for a fully integrative neuroscientific perspective at the practical level of clinical psychiatry, dualism's special contribution, in contrast to materialism, is the proposition that a person is more than the sum of their material parts. A materialist account cannot separate a patient from the neurological processes from which their difficult behaviours arise. Dualism, on the other hand, allows us to view our patients as persons afflicted by neural dysfunction that is separate from and inessential to who they really are. And if this is the case, then perhaps we stand a better chance of seeing through the pathology to the person it besets.