The logic of delusion

Piagetian concepts explaining normal mental development are applied to delusion, a major psychiatric disorder of thought which can result in bizarre conduct. Piaget constructed problems in which the errors of six to eight year old children fit the standard textbook definition of delusion surprisingly well. When we examined cases of delusional individuals, we concluded that their apparent irrational and bizarre conduct could be explained as problem-solving errors like those of Piaget's young children. In contradistinction to existing theories, we define delusion as a regression under stress to the logic of children of a particular age range, and that what appears bizarre and irrational is the result of an adult attempting to filter experience through a child's logic.Under a different title this paper was presented at the Biennial Congress of the World Federation for Mental Health in Mexico City in August, 1991.