Epistemological aspects of delusional thinking

The notion of a delusion occupies a central place in psychotherapy. The presence of delusional thinking in a patient is often regarded as indicative of psychosis. And yet, the nature of a delusion is still widely disputed. The difficulty of defining a delusion has proved so difficult that some prominent authors have declared the task impossible. The aim of this paper is to offer a characterisation of delusional systems of thought. In this paper is argued that delusions, unlike scientific explanations and the explanations generally offered by common sense, fail to minimise that which requires explanation. In the first part of the paper, difficulties with extant accounts will be discussed. In the following parts, the author's own account of delusional thoughts will be developed and some difficult cases considered. It will be argued that delusions differ from more typical beliefs in the number of things that they leave unexplained. Delusions, unlike those beliefs we typically see as rational, bring about an increase in the number of things requiring explanation.