Posted by alexandra_k on August 17, 2005, at 23:04:37
In reply to Re: Dead Certainty in the Cotard Delusion, posted by Toph on August 17, 2005, at 22:07:05
In their paper ‘Monothematic Delusions: Towards a Two-Factor Account’ Davies et al., consider that while an anomalous experience may be necessary for delusion, it cannot be sufficient. They maintain that some people have comparable anomalous experiences, yet they do not exhibit comparable delusions. While they agree that such an anomalous experience is in need of explanation they do not consider the experience to be sufficient to determine that the person must arrive at a delusional explanation for it.
Davies et al., consider that the account thus far would seem to go some of the way towards explaining why it is that the delusional hypothesis occurs to the subject. They also maintain, however, that the above account is not enough to explain why it is that the delusional subject accepts the delusional hypothesis as a belief ‘despite everything they previously knew to be true’ and despite other people attempting to persuade them out of their delusion. As such they consider that while the account thus far may go some of the way towards explaining how it is that the delusional hypothesis occurs to the subject, the account must be supplemented by a second factor to explain how it is that the subject comes to be certain that they are in fact dead, or why they persist in making their delusional utterance.
One route to belief is the route from perception to belief. While this input clause is not typically considered to be a rationality constraint we can consider whether we would call someone irrational who failed to form beliefs in this way. Suppose I am in a room walking around and I fall over a chair. You ask ‘what happened? Didn’t you see the chair?’ I reply ‘Oh, I saw it alright; I just didn’t believe it was there’. In this case I might be described as being irrational for failing to believe what I had perceived. Whether we consider this to be a failure of rationality or not it does seem that something abnormal is going on here.
It would also seem that it is not a normal, rational, or typical response to always believe what we perceive, however. Sometimes what we perceive diverges too radically from what we previously knew to be true. It diverges too much from our prior beliefs and perceptions. When we experience visual illusion it may well be a typical initial response to judge the lines to be of different length when viewing the Muller Lyer illusion. Once we come to understand something of how the illusion is produced, however, or once we see the arrows removed and reinserted then we no longer believe what we perceive. We judge the lines to be of equal length despite the way that they appear to us to be.
Davies et al., consider various suggestions that have been offered as accounts of the nature of the second factor. They settle on the line where the delusional error is to ‘accept an anomalous perceptual experience to be veridical when there is rational grounds to doubt its veridicality’. In considering the anomalous experience to be a perceptual experience Davies et al., are led into the problem of the unwanted prediction. They acknowledge that a problem with their account is that it would predict that a person with the Cotard delusion should be routinely fooled by the Muller-Lyer illusion as they come to believe what they perceive. The subject with the Cotard delusion should be unable to inhibit this response despite coming to learn about how the illusion is produced, and despite perceptual information to the contrary such as seeing the arrow heads removed and then reinserted.
One way around this problem for Davies et al’s account of the nature of the second factor would be to consider that the anomalous experience need not be perceptual. Indeed, from what we do know about the various kinds of anomalous experiences that seem to feature in the production of various kinds of delusion it seems that in the clear majority of cases the experiences have more to do with the persons affective response system or levels of physiological arousal rather than with perceptual deficit.
So the way that Maher told the story we have a neurophysiological deficit that produces an anomalous experience. Because the experience is intense and prolonged the subject is compelled to attempt to explain it and they thus develop a delusion. The way that Davies et al., tell the story is similar with respect to there being a neurophysiological deficit that produces an anomalous experience for the delusional subject. They also maintain that the delusional subject accepts their experience as veridical as normal subjects do. The delusional error, however, is that we would expect them to be able to inhibit this ‘believe what you perceive’ response when what they believe diverges too radically from everything they previously knew to be true. The delusional subject should be able to take evidence that runs contrary to their delusion and thus come to see that their delusion is false.
poster:alexandra_k
thread:543149
URL: http://www.dr-bob.org/babble/write/20050807/msgs/543255.html