Defining Delusion

Edgar Jones argues that psychiatry has failed to define the notion of delusion. This failure raises doubts about whether we can use delusions as a guide in identifying psychosis. Lacking a definition, our claims to identify delusions and diagnostic inferences based on those claims are suspect. Jones suggests that we can do a better job of distinguishing delusions from other sorts of cognitive phenomena, normal and abnormal, by considering a wider range of possible contrasts between delusions and other cognitive states. Though he does not provide a definition, I think that he develops a promising approach to the problem he is trying to solve. However, accounts of delusion in the psychiatric literature often take aim at a different problem. Failing to acknowledge this difference, Jones somewhat misconstrues the accounts he criticizes. Nor is it clear that solving his problem will be of much help in solving the other problem.

Delusion does more than serve as a sign of madness: it is constitutive of madness, or at least of some forms of madness. To paraphrase Jaspers, to be deluded is to be mad. What is it about delusions that leads us to say that the deluded are mad? To answer this question we must explain how delusions differ from “normal” beliefs, i.e., beliefs whose acceptance does not constitute insanity. Therein lies the connection between Jones’s project and the above problem. However, we need not identify characteristics that distinguish delusions from other “abnormal” cognitive states such as overvalued ideas or obsessive thoughts. Indeed, since such states also constitute madness, we would hope to find that they have characteristics in common with delusions. Further, were we able to cite characteristics that distinguish delusions from other normal and abnormal cognitive states, these would not necessarily help us explain what’s crazy about delusions.

In my reading, Fulford’s discussion of delusions (1989) and, to a large extent, Taylor’s account (1979) address the problem described above. Jones treats these as proposals for defining delusion, i.e., as attempts to identify characteristics that distinguish delusion from other cognitive states. But such is not the goal of these “definitions” of delusion. If they are unsatisfactory, it is not because they fail to provide necessary and sufficient conditions for something being a delusion. That said, it might well be true that attempts to explain why delusion constitutes madness would benefit from considering a broader range of characteristics of delusions. But even if we devise a criterion that distinguishes delusion from other cognitive phenomena, normal and abnormal, nothing guarantees that we could explain what makes delusions crazy in terms of the characteristics mentioned in that definition.

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