The Rationality of Delusions

In the talk on the video, my co-author Angeles Eraña assume delusions are beliefs and argue that they have an important rational aspect. To this aim, we will draw on a distinction among different senses of ‘rationality’ one of us has already developed (Eraña 2009). We will argue that delusions are not rational in the externalist sense of being the product of a well-functioning reliable cognitive system. On the contrary, there is ample evidence that some cognitive malfunctions are involved. Furthermore, they are not rational in an internalist, deontological sense either, since this sort of rationality requires the agent to have a well-functioning conscious, control system (corresponding to S1 in dual system theory), and delusional agents’ conscious control systems are too tied to the false and recalcitrant delusional belief. 

One might wonder, once we accept that delusions are rational neither in the internist sense of giving us epistemic justification nor in the externist sense of being the product of a well-functioning relieable mechanism, in what sense could they be rational? We will argue that there is a third sense, in which delusions are rational. This third sense depends on the effects and aims of the delusion, which is to recover a sufficient condition for human rationality: the well-functioning of S1. In this sense, delusions are rational and adaptive.