Thursday 2 May 2019

Delusions and Beliefs

Today's post is by Kengo Miyazono, Hiroshima University, who talks about his latest book, Delusions and Beliefs (Routledge 2018).

This book addresses the following theoretical questions about delusions:

(1) The Nature Question: What is a delusion? In particular, what kind of mental state is it? The standard view in psychiatry is that delusions are beliefs. But, is this view (‘doxasticism about delusion’) really true? Delusions have a number of peculiar features that are not belief-like, such as the remarkable insensitivity to evidence. Are these peculiar features consistent with the doxastic conception of delusions?

(2) The Pathology Question: Delusions are pathological mental states. Delusions, together with other symptoms, warrant clinical diagnoses and treatments. Why are delusions pathological? What distinguishes pathological delusions from non-pathological irrational beliefs? Are delusions pathological because they are too irrational? Or, are they pathological because they are too strange?

(3) The Etiology Question: What is the cause of a delusion? How is it formed? It is widely believed that delusions (at least many of them) are formed in response to some abnormal experience. But does abnormal experience explain everything about the process of delusion formation? Is abnormal experience sufficient for someone to form a delusion? If not, what are the additional factors?

In the previous debates on delusions, these questions tend to be discussed independently from each other and in relation to different lines of inquiry. The nature question has been discussed mainly in the philosophy of mind; the etiology question, in contrast, has been examined in psychiatry and cognitive science; and the pathology question has been a topic in the philosophy of psychiatry. However, discussing these questions separately is potentially problematic because the answer to one question can have implications for how another question is answered. In this book, I take the connections between the three questions very seriously. My discussions of the questions are interrelated in such a way that my answers to them constitute a unified and coherent understanding of delusions.

The central hypothesis of this book, which I call ‘the malfunctional belief hypothesis’, is that delusions are malfunctional beliefs. They belong to the category of belief and, hence, doxasticism is correct (which is my answer to the nature question). However, unlike non-pathological irrational beliefs, they fail to perform some functions of belief (which is the crucial part of my answer to the pathology question). More precisely, delusions directly or indirectly involve some malfunctioning cognitive mechanisms. And the two-factor account of the delusion formation process (which answers the etiology question) makes the malfunctional belief hypothesis empirically credible.

The category of heart, according to one view, is defined in terms of the distinctively heart-like function; i.e., the function of pumping blood. All (and only) members of this category have the function of pumping blood. But this does not mean that all the members of this category actually perform the function of pumping blood. Diseased or malformed hearts have the function of pumping blood and thus belong to the category of heart, but they do not perform the function. In other words, they are malfunctional hearts. 

A delusion, according to my hypothesis, is analogous to a diseased or malformed heart. The category of belief, just like the category of heart, is defined in terms of distinctively belief-like functions, which I call ‘doxastic functions’. This is the basic idea of teleo-functionalism, which is the theoretical foundation of this book. All (and the only) members of the category of belief have doxastic functions. 

But this does not mean that all the members actually perform the functions. Delusions, according to my hypothesis, have doxastic functions and thus belong to the category of belief, but they do not perform the functions (or, more precisely, delusions directly or indirectly involve some cognitive mechanisms that fail to perform their functions). They are malfunctional beliefs. 

Here is a brief overview of the main chapters:

Chapter 2 Nature. The central puzzle concerning the nature question comes from a seemingly incoherent pair of ideas: (1) delusions are beliefs and (2) delusions have a number of features that are not belief-like. Both ideas are at least prima facie plausible, but there is a clear tension between them. One solution to the puzzle is to endorse one and deny the other. This ‘incompatibilist’ response assumes that the two ideas are not compatible with each other and hence at least one of them should be rejected. 

Teleo-functionalism about beliefs, on the other hand, suggests an alternative, ‘compatibilist’ response according to which the two ideas do not rule out one another. There is nothing incoherent with the idea that diseased or malformed hearts belong to the category of heart despite the fact that they have some features that are not heart-like; e.g., failing to pump blood. Similarly, according to teleo-functionalism, there is nothing incoherent with the idea that delusions belong to the category of belief despite the fact that they have some features that are not belief-like. (See also this entry.)

Chapter 3 Pathology. This chapter (which is based on this paper) explores the features of delusions that are responsible for their being pathological. First, I critically examine the proposals according to which delusions are pathological because of their strangeness, their extreme irrationality, their resistance to folk psychological explanations, and the impaired responsibility-grounding capacities of people with delusions. The proposals are problematic because they invite some counterexamples as well as theoretical difficulties. 

An alternative account comes from Wakefield’s harmful dysfunction analysis of disorder, according to which a disorder is a condition that involves harmful malfunctions (or dysfunctions). Congestive heart failure, for example, is a disorder because a heart is harmfully malfunctioning in that condition. Following Wakefield, I argue that a delusion is a disordered or pathological mental state because it is a harmfully malfunctional state. (See also this entry.)

Chapter 4 Etiology. This chapter defends the two-factor theory, according to which, in addition to abnormal experience, something else is also needed to explain the process of delusion formation. I offer an inference-to-the-best-explanation argument for the two-factor theory. Among other theories, the two-factor theory provides the best explanation of relevant empirical and clinical observations. 

I also discuss the prediction-error theory, which is another influential theory of the process of delusion formation. I show that the central ideas of the prediction-error theory can be incorporated in the two-factor framework to form a hybrid theory. The hybrid theory does not only inherit the theoretical and empirical merits of the two-factor theory and the prediction-error theory, but also provides a unified account of many kinds of delusions, including the ones that are explained by the two-factor theory and the ones that are explained by the prediction-error theory. (See also this entry.)

1 comment:

  1. The question is always - how does verbal behavior measurably predict actual behavior. Very little or folks do the opposite of what they say. Thus, language/statements/"beliefs" are epiphenomenal or contra indicators/trivial. For example, 70% of American say Satan is alive on earth/guardian angels - but no one ACTS according to those claims. No one let's"jesus" fix their plumbing or fly an airplane.


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