The Measure of Madness
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From Life and Mind: Philosophical Issues in Biology and Psychology

The Measure of Madness

Philosophy of Mind, Cognitive Neuroscience, and Delusional Thought

By Philip Gerrans

Drawing on the latest work in cognitive neuroscience, a philosopher proposes that delusions are narrative models that accommodate anomalous experiences.

A Bradford Book





Drawing on the latest work in cognitive neuroscience, a philosopher proposes that delusions are narrative models that accommodate anomalous experiences.

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

Gerrans proposes that delusions are narrative models that accommodate anomalous experiences. He argues that delusions represent the operation of the Default Mode Network (DMN)—the cognitive system that provides the raw material for humans' inbuilt tendency to provide a subjectively compelling narrative context for anomalous or highly salient experiences—without the “supervision” of higher cognitive processes present in the nondelusional mind. This explanation illuminates the relationship among delusions, dreams, imaginative states, and irrational beliefs that have perplexed philosophers and psychologists 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 through the cognitive system, and applies these to case studies of typical schizophrenic delusions: misidentification, alien control, and thought insertion. Drawing on the interventionist model of causal explanation in philosophy of science and the predictive coding approach to the mind influential in computational neuroscience, Gerrans provides a model for integrative theorizing about the mind.


$42.00 S ISBN: 9780262027557 304 pp. | 8 in x 5.375 in 3 b&w illus.


  • A first-rate exploration of how reference to multiple levels of explanation and description, from phenomenology to chemistry, may be assembled into a synoptic theory of delusion. Gerrans offers an erudite, novel, and insightful approach to the whole topic of delusional thought and attitude. This is an important book that deserves to be widely read.

    George Graham

    Professor of Philosophy and Adjunct Faculty, Neuroscience Institute, Georgia State University; author of The Disordered Mind; and coeditor of The Oxford Handbook of Philosophy and Psychiatry

  • An elegant meditation on delusion, dreaming, and default-mode thought. From dopamine dysregulation to delusional mood, from predictive coding to the phenomenology of agency, The Measure of Madness paints a compelling picture of thought gone wrong. This is philosophically informed cognitive neuropsychiatry at its best.

    Tim Bayne

    Professor of Philosophy, University of Manchester

  • Philip Gerrans's wonderful book not only presents an original and rigorously well-informed account of some of the most persistent and perplexing psychiatric delusions discussed by philosophers and cognitive scientists; it also shows how to develop a philosophical model of the mind that takes into account the functional, neural, and biochemical bases of mental capacities. Writing in an elegant but accessible style, and showing a mastery of the philosophical and the neuroscientific literature, Gerrans advocates an integrative approach to psychological mechanisms, as opposed to seeing the neural and the psychological levels as autonomous and independent of each other. Gerrans has persuaded me that this is the way to understand psychiatric delusions; and his approach to delusions also shows, more generally, the value of the integrative approach to studying the mind. I cannot recommend this book too highly.

    Tim Crane

    Knightbridge Professor of Philosophy, University of Cambridge