Wednesday, 22 May 2013

Delusions as Malfunctioning Beliefs

Kengo Miyazono
with Charles Darwin
I am a research fellow at University of Birmingham and a JSPS (Japan Society for the Promotion of Science) fellow. My main research area is philosophy of mind, broadly construed (including philosophy of psychology, philosophy of psychiatry and early modern philosophy of mind). Recently, I am working on a project which is, directly or indirectly, related to epistemic innocence project.

The aim of this project is to present and develop a new strategy to defend doxasticism about delusion from the main argument against it. Doxasticism about delusion is the view that delusions are beliefs.

Although this view is widely accepted in psychiatry, there is a simple but powerful philosophical argument against it. I call it “the argument from causal role”.
- Playing a belief-like causal role is necessary for a mental state to be a belief.
- Many delusions fail to play belief-like causal roles.
- Therefore, many delusions are not beliefs.

The first premise directly comes from functionalism about belief, which is still the most popular view of belief. Second premise comes from clinical observations. It has been reported that, for instance, delusions are not very sensitive to evidence, they sometimes fail to guide non-verbal behavior, and they often fail to be coherent with other beliefs and emotions.

Many philosophers in the literature accept this argument and reject doxasticism (e.g. Gregory Currie, Andy Egan, Eric Schwitzgebel). Other philosophers resist the argument by rejecting the second premise (e.g. Lisa Bortolotti).


The main aim of this project is to explore the other option that has’t been (seriously) explored yet, namely, the option of resisting the argument by rejecting the first premise. I propose an alternative theory of belief according to which playing a belief-like causal role is not necessary for a mental state to be a belief. (See David Lewis on “mad pain” for a similar attempt.) The theory is a version of teleological theories of mind (e.g. Ruth Millikan) and it is called “teleo-attitude functionalism (TAF)”.

According to TAF, what is necessary and sufficient for a mental state to be a belief is to have the function of playing a belief-like causal role, not to actually play the role. And it is possible that a mental state has the function of playing a belief-like causal role without actually playing the role (= malfunctioning belief) for the same reason that, for instance, it is possible that a human organ has the function of pumping blood without actually doing it (=malfunctioning heart).

TAF rejects the first premise of the argument from causal role, because actually playing a belief-like causal role is not necessary for a mental state to be a belief according to the theory. Even if many delusions fail to actually play belief-like causal roles, it doesn’t rule out the possibility that they are nonetheless (malfunctioning) beliefs, for the same reason that even if a human organ fails to actually pump blood, it doesn’t rule out the possibility that it is nonetheless a (malfunctioning) heart.

I also argue for the following additional claims.


The major objections to TAF (e.g. Swampman objection) are not very persuasive and, thus, it is a good theory of belief. Under TAF, there are some reasons to favor doxasticism over other alternative views such as imagination-view (Currie) or bimagination-view (Egan).

The idea that delusions are malfunctioning beliefs is helpful in explaining the fact that delusions are pathological phenomena, especially when the idea is combined with the influential view, proposed and defended by Jerome Wakefield, that harmful malfunctioning is the essential feature of disorder.
TAF can be generalized and applicable to other kinds of mental states such as desires, emotions or moods. In doing so, we can conceptualize other (symptoms of) mental disorders as other instances of malfunctioning mental states. For instance, pathological anxiety in anxiety disorder can be conceptualized as malfunctioning anxiety.

2 comments:

  1. Hi Kengo,

    This was really interesting (especially because I too am interested in whether an appeal to Millikanian function can inform what we might say about belief).

    So if we say that beliefs have the proper function of playing a given causal role, and that’s necessary and sufficient for something to count as belief, then we can also say in response to the anti-doxasticist about delusion that just because delusions do not always play a given causal role, that does not count against their belief status. So if delusions really do have the same proper function as ordinary beliefs, then the argument from causal role will fail.

    But what justifies the claim that delusions do have that function? Doesn’t it need to be the case that they are produced in roughly the same way (i.e., by the same mechanisms) as ordinary belief? But isn’t that precisely the kind of claim that an anti-doxasticist would deny? The anti-doxasticist could agree with you that what makes something a belief is its having the proper function to play a causal role. But couldn’t they also claim that delusions do not have that function, because they are not produced under what Millikan calls ‘Normal' conditions?

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  2. Hi Ema,

    Thanks for the excellent question! Here is my basic idea on this.

    I define the functions of mental states in terms of the functions of the producers (i.e. the mechanisms that produce the states) and the consumers (i.e. the mechanisms that use the states for various purposes) in a roughly Millikanian way.

    In this picture, in order to show that delusions have the relevant function, we need to show that delusions have a right kind of producers and consumers. Roughly speaking, delusions have the relevant function if they are produced and consumed by the same mechanisms that produce and consume normal beliefs.

    Then, are delusions produced and consumed by the same mechanisms that produce and consume normal beliefs? I take this to be an open empirical issue. At the same time, though, it seems to me that many models of delusion formation in cognitive neuropsychiatry assume that delusions are produced by the same mechanisms that produce normal beliefs. Presumably those mechanisms are malfunctioning in delusional subjects. Still, these are the same mechanisms as the ones that produce normal beliefs, for the same reason that a malfunctioning heart is the same organ as the well-functioning one. Again, the fact that delusional subjects show various kinds of biases in normal judgments (such as JTB bias) seem to suggest that delusions are produced by the same mechanisms that produce normal beliefs.

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