Delusions and Other Irrational Beliefs

Delusions and Other Irrational Beliefs (International Perspectives in Philosophy & Psychiatry) was published by Oxford University Press in November 2009. It was awarded the American Philosophical Association Book Prize in 2011.

A symposium on the book appeared in a special issue of Neuroethics (2012).

The book was also included in the Current World Literature published by Current Opinion in Psychiatry, 24 (6), 2011, and rated as "of outstanding interest" (category History & Philosophy > Recent developments in naturalizing the mind).

An interview about the book conducted by Raj Persaud is available here: Are delusions that irrational?

DOIB book cover


Review by Jennifer Radden, Metapsychology Online, 17 July 2010.

Extract: "Much interesting recent material about delusions has come to us - from philosophers of mind and psychology, from experimental and cognitive psychologists, and from many whose work straddles, and blurs, such disciplinary boundaries. Lisa Bortolotti’s book on delusions and other irrational beliefs (OUP 2010) stands out among this material for its clarity, acumen, freshness, and sweep. It is well written and organized, carefully argued, independent and original in its perspective, and fair-minded in its appraisals. It redirects theoretical attention from one, widely accepted paradigm (delusions as irrational beliefs), to another (delusions as disturbances of self knowledge and cognitive authority). And finally, it has the merit of providing lengthy clinical case material sufficient to illustrate the theoretical points made."

Review by Peter Langland-Hassan, Psychological Medicine, 40, 2010.

Extract: "Clinical researchers interested in delusions have much to gain from this well-researched and empirically informed meditation on the many similarities between delusions and 'everyday' irrational beliefs - one driven as much by research as by work on psychiatric cases."

Review by Luca Malatesti, Journal of Applied Philosophy, 28(1), 2011.

Extract: "This books offers a significant and successful example of the emerging 'new' analytic philosophy of psychiatry. Methodologically, it exemplifies a fruitful two-way interaction between philosophy and empirical investigation. Empirical results from cognitive sciences and clinical research are used to constrain philosophical assumptions about beliefs and delusions. Rigorous philosophical argumentation is employed to clarify and adjudicate theoretical interpretations of empirical data concerning delusions. This work is surely an obligatory reading for those seriously interested in delusions, beliefs and, more in general, the application of an empirically informed philosophy of mind to psychiatry."

Review by Femi Oyebode, British Journal of Psychiatry, 198, 2011.

Extract: "This is probably the best treatise in recent times on the subject of delusions. Bortolotti brings her professional expertise to bear on a subject that is central to our understanding of what it means to be severely afflicted with schizophrenia or any psychosis. What is remarkable is that Bortolotti has mastered the literature on delusions as a psychopathological phenomenon. She does not treat delusions merely as an excuse for high-flown philosophical arguments, but takes the reality of delusions seriously, recognising that the empirical facts about delusions are important and that philosophical enquiry ought to ‘make sure that the theory to be developed is compatible with the relevant empirical data’ (p. 7). This is a refreshing approach from a philosopher."

Review by Elisabetta Sirgiovanni, HumanaMente, 20, 2012.

Extract: "This book is an important contribution to the recent delusion debate. The book can also usefully work as a cognitive science textbook on delusion. The author introduces the topic in depth, covering all the right issues in a way that no one has done before. The bibliography is also an extremely rich guide for those interested in further exploring the subject, and also for finding sources relevant to disputes in the philosophy of mind."

From 'Reading about Philosophy of Psychiatry' by Matthew Broome, The Psychiatrist Online, August 2013:

"One of the most important works on delusions is Bortolotti’s Delusions and Other Irrational Beliefs, a book that examines the core features of delusions in relation to other mental states, demonstrating that many non-delusional beliefs are not so rational and delusions often differ in degree, rather than kind, from other, non-pathological, beliefs."

Review by Emily Barrett and Cory Wright, Philosophical Quarterly 2014.

Extract: "Delusions has great merit, and has really driven the new interdisciplinary research in philosophy of psychiatry. It is a model contribution to this literature for philosophically minded clinicians and clinically minded philosophers, as well as philosophers of mind and naturalistic epistemologists concerned with conditions on belief ascription."



1: The Background

2: Procedural Rationality and Belief Ascription

3: Epistemic Rationality and Belief Ascription

4: Agential Rationality and Belief Ascription

5: Beliefs and Self Knowledge

6: Conclusions

Bibliography and Reference List



Delusions and Other Irrational Beliefs is a contribution to the debate about the nature of delusions and to the literature on the conditions for belief ascription.

Of the numerous challenges to the view that delusions are beliefs, many are due to the conviction that there needs to be a background of rationality in the behaviour of the people to whom we ascribe beliefs. The view is that delusions cannot be beliefs because: (a) they are badly integrated with the subject’s other intentional states; (b) they are not supported by and responsive to the evidence available to the subject; (c) they are not endorsed with good reasons or consistently acted upon.

In the book I attempt to show that the arguments against the doxastic conception of delusions are misleading when they are based on an idealised notion of belief, and I present many examples of irrationality in paradigmatic cases of belief. As a result, I maintain that we should give up (once and for all) the assumption that belief ascription is hostage to the satisfaction of norms of rationality.

By bringing together recent work in philosophy of mind, cognitive psychology and psychiatry, the book offers a comprehensive review of the philosophical issues raised by the psychology of normal and abnormal cognition, defends the doxastic conception of delusions, and develops a theory about the role of judgements of rationality and of attributions of self-knowledge in belief ascription.