Friday 18 October 2013

Delusions: Not on a Continuum with Normal Beliefs

Tony David
Delusions are the hallmark of madness. Coming up with a precise definition of ‘delusion’ is nevertheless difficult and perhaps impossible, especially when concerned exclusively on epistemology (David, 1999). 

Most aspects of standard definitions have exceptions on which clinicians in practice agree. The notion that delusions like other psychotic phenomena are best viewed as lying on a continuum with normal beliefs is appealing but flawed (David, 2010). Delusions are multiply determined with many typical features but none essential and / or invariable. Delusions are more than the sum of their epistemic features. They are clinical phenomena that require a huge amount of contextual information before they can be understood (or before it can be concluded that they are un-understandable!). Sometimes a statement that would only be weakly eligible to be called a delusion, passes this threshold because the person expressing the utterance shows evidence of psychosis on other grounds. This 'reverse reasoning' would be wholly inadmissible epistemologically but is perfectly acceptable and indeed sensible in a clinical context. 

The delusion should be considered to be akin to ‘a syndrome’ and has similar utility.
David AS (1999) On the impossibility of defining delusions. Philosophy, Psychiatry, & Psychology, 6 (1), 17-20.
David AS (2010) Why we need more debate on whether psychotic symptoms lie on a continuum with normality. Psychological Medicine, 40: 1935-42.

1 comment:

  1. Thank you Tony for your post! I agree with you that it is very difficult to define (especially demarcate) delusions on epistemic grounds, and that in order to understand a delusion one needs a lot of contextual information. But I think that's true of normal beliefs as well.

    Maybe because I have always been impressed by the amount of irrationality normal beliefs are subject to, I have tended to see delusions on a continuum with them. Recently and by mere chance I found this quote by Erasmus (The Praise of Folly, 1509): "I doubt if a single individual could be found from the whole of mankind free from some form of insanity. The only difference is one of degree. A man who sees a gourd and takes it for his wife is called insane because this happens to very few people." I'm drawn to this view, although I also see the advantages of yours.


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