Understanding the clinical concept of delusion: from an estranged to an engaged epistemology.

Delusion is relatively easy to diagnose but near impossible to define. This paper (I) uses the method of 'philosophical fieldwork' to show that standard approaches use definitions that are both over- and under-inclusive. It argues furthermore that such approaches typically presuppose what is here dubbed an 'estranged' epistemology. This epistemology supposes that our understanding of the world occurs outside of, and consequent on, our experience of it. Instead of this an alternative 'engaged' epistemology is set out. This alternative sees experience itself as the vehicle of our most fundamental comprehending engagement with the world. (II) This, it is argued, makes better sense both of our contact with reality and of the failure of this contact in delusion. (III) The implications of this alternative theorisation for the cognitive psychology of delusion are discussed.