Response to Commentaries

Both clinicians and philosophers are agreed that delusion is a key symptom of psychosis. However, there is great disagreement over the nature of delusion, and what it is about delusion that leads us to infer madness in some of those who express these abnormal beliefs. Anthony David has commented on the weakness of current definitions and argued that it is the “secondary aspects” of delusion (the processes underlying their formation, the person’s attitude to these beliefs and the effect that they have on them) that may help us to draw clearer distinctions. This position is shared by Nassir Ghaemi who suggests that empirical research will progressively change our understanding of delusion and that this too will impact on the diagnosis of psychotic disorders.

Lynn Stephens rightly draws a distinction between testing delusions to discover more about their inherent characteristics and analyzing them as manifestations of psychosis. He notes that Fulford’s definition of delusion (1989) was in essence designed to explore what it is about madness that is truly different. The observation by Fulford that they may be considered as “value judgements” with a generic relationship to defective reasons for action follows from an attempt to explain irrational and sometimes bizarre behavior which, nevertheless, makes great sense to the subject. It is less certain that Taylor (1979), the author of a textbook on the causes and symptoms of psychopathology, had this goal in mind when he identified five “characteristics” that defined delusion. Stephens also questions the necessity of comparing delusions with overvalued ideas and obsessions since “such states also constitute madness.” Few psychiatrists would concur with this statement. Obsessionals and anorectics are not usually considered psychotic even though they may suffer from distressing and disabling disorders.

David and Ghaemi raise the important question about the formation of delusion and the nature of the thought processes that underlie this phenomenon. Currently there are two positions: either that delusions in psychotic states are the product of a specific “defect” related to a neurophysiological abnormality, or that they are the result of cognitive bias, which involves the processing of information in a preferential manner (Bentall 1995). The former implies a distinct hiatus between normality and psychosis, whereas the latter suggests a continuum running through a range of psychological disorders differentiated by degrees of severity. If the latter proves to be the case, it is important not only to test delusions and normal beliefs but also other idiosyncratic mental states to map a range of presentations.

The related question—what is it about delusion that constitutes madness—was not the aim of my study. It remains, however, a significant issue and one, if resolved, that could shed considerable light on the nature of delusion. David has drawn attention to the role of insight in linking delusion with psychosis (1990). The implication is that the deluded person has lost something of the ability to make careful judgements about his or her beliefs and behavior in relation to others. Delusion can be seen as a personal conviction, often of great significance, that overrides pre-existing beliefs that an individual may hold about themselves in a broader context. Cutting has suggested that delusional mood represents a breakdown in the subject’s Gestalt of his surroundings, and occurs when objects and places appear to stand out or appear curiously at variance with their situation, though there had been no obvious change in their appearance (1989). From feeling mildly discontented with work and having a grievance against some colleagues, for example, the person in a paranoid state may come to believe that there is a conspiracy against him and begin to behave in a way that his companions consider to be out of character and at odds with the facts. With the return of insight, the person becomes aware that his recent experiences have been subject to distortion and that something untoward has happened.

Stephens comments that I did not offer a definition of delusion. While important research remains to be undertaken on other characteristics, the mechanisms of delusion formation and contrasting forms of belief, it would be premature to advance yet one more definition. As David observed, we...