Tuesday 26 January 2021

Against Defining Delusion

Today's post is by Sam Wilkinson. You can read Sam's recently published paper, Expressivism about Delusion Attribution, in the European Journal of Analytic Philosophy. It appeared in a special issue on the Bounds of Rationality.

Sam Wilkinson

What is delusion? While we can point to paradigmatic cases, we have struggled to produce an uncontentious definition of delusion. In my paper, I argue that we shouldn’t have been trying to define delusion in the first place, and that it becomes clear why, once we reflect on the sort of concept that delusion is.

Delusion attribution, e.g. saying “This person is delusional”, is not (fully) fact-stating. It is not like saying “This person is 6ft tall”. It is fundamentally an evaluation. Some evaluations involve failing to adhere to an objective benchmark, while others are more fundamentally, irreducibly evaluative. One way of thinking about these fundamental kinds of evaluations is as expressive, rather than descriptive.


To simplify somewhat, delusion attributions are more akin to expressions of folk-epistemic bafflement. Why think that this is so? And what are the consequences of this?

First of all, it seems like delusion expresses a negative evaluation. Consider a hyperbolic use among friends (“You’re delusional if you think Manchester Utd. will win the Premiership!”). Now, one might object that, while this is an expressive use of “delusion”, this is not at all how psychiatrists use the term. Nevertheless I would insist that the calm, institutional use of the term only masks its true nature.

Secondly, as with expressivists in meta-ethics, who are motivated by a metaphysical unease with postulating moral properties we might be similarly reluctant to countenance properties of “delusionality”.

What are the consequences of the view?

First, an inability to define is to be expected. Why think that all of the many things that arouse negative reactions from our folk-epistemic sensibilities can be regimented under a strict definition?

In a related manner, if you try to characterize the sorts of things that get called delusions, you get a sort of disjunctive norm pluralism. Put simply, there are different kinds of folk-epistemic badness, but once a threshold is reached, you call that thing a delusion. Contrast, for example, reverse Othello syndrome with a bizarre delusion in the context of psychosis. You might, for example, think about the implausibility of the content. Here, the bizarre delusion (“I am the left foot of God”) scores highly, so highly in fact that you don’t even need to ask yourself about the individual’s grounds for the claim. (Though interesting, it wouldn’t remove delusional status.) In contrast, if somebody said “My wife is being faithful to me”, this is true (one hopes) of many people, and it could only be an examination of their personal situation, their resistance to evidence, etc. that would then tip them into delusional territory.


Since delusion attribution is an expression of bafflement, understandability takes precedence over rationality. A mother who is reluctant to believe that her son is a murderer may exhibit profound levels of epistemic irrationality, but we understand that people are reluctant to admit the guilt of loved ones. Indeed, we’d find an impartial acceptance of the evidence more troubling!

What does this mean for delusions researchers? Not much. Keep up the great work on paradigm cases of delusion. Just don’t worry about defining it.

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