Predicting the weather.(Letters)(Letter to the Editor)

SIR: Paul Monk's valuable and admirable article "Meriwether and Strange Weather" (April 2004) has it nearly right, but not quite.

Monk proposes that people try to maintain their beliefs, regardless of new evidence. This could not be right; evolution would have weeded out such a species. Animals learn according to a realistic criterion in order to survive.

Monk proposes that the human species tends to be over-confident. He is partly mistaken. The fact is the human species is very variable, some being at some times overconfident, and some at some times being under-confident. Monk would be nearer the mark to say that societies sometimes are constructed so that over-confident persons get to dictate public policy: yes, indeed, the world is largely run by criminals and fools, but not all humans are always criminal and foolish.

While rightly pointing out that they have not developed their intellectual virtues, Monk misses the fundamental fact that people maintain their desires, not simply their beliefs. This persistently and consistently causes them to assess all new factual evidence with a maintained bias, and leads to new beliefs being consistent with old ones only insofar as they seem to support the maintained desires. Such maintained desires are sometimes called neurotic. They cause people to view the world through rose-coloured spectacles, or to be melancholy at times. They are caused by faulty upbringing.

Decision theory assesses probable benefit as a sum of products of a subjective probability and a hypothetical subjective benefit. A person who is sane but has not developed full intellectual virtue will often shift the subjective numbers back and forth between the two members of such a product, the subjective probability and the subjective hypothetical benefit. Full intellectual virtue ...