The Measure of Madness ─ Philosophy of Mind, Cognitive Neuroscience, and Delusional Thought

In The Measure of Madness, Philip Gerrans offers a novelexplanation of delusion. Over the last two decades, philosophers and cognitive scientists haveinvestigated explanations of delusion that interweave philosophical questions about the nature ofbelief and rationality with findings from cognitive science and neurobiology. Gerrans argues thatonce we fully describe the computational and neural mechanisms that produce delusion and the way inwhich conscious experience and thought depend on them, the concept of delusional belief retains onlya heuristic role in the explanation of delusion.

Gerrans proposes that delusionsare narrative models that accommodate anomalous experiences. He argues that delusions represent theoperation of the Default Mode Network (DMN) -- the cognitive system that provides the raw materialfor humans' inbuilt tendency to provide a subjectively compelling narrative context for anomalous orhighly salient experiences -- without the "supervision" of higher cognitive processespresent in the nondelusional mind. This explanation illuminates the relationship among delusions,dreams, imaginative states, and irrational beliefs that have perplexed philosophers andpsychologists for over a century. Going beyond the purely conceptual and the phenomenological,Gerrans brings together findings from different disciplines to trace the flow of information throughthe cognitive system, and applies these to case studies of typical schizophrenic delusions:misidentification, alien control, and thought insertion. Drawing on the interventionist model ofcausal explanation in philosophy of science and the predictive coding approach to the mindinfluential in computational neuroscience, Gerrans provides a model for integrative theorizing aboutthe mind.

Philip Gerrans is Professor of Philosophy at the University of Adelaide.