Recent clinical trials show that psychedelics such as LSD and psilocybin can be given safely in controlled conditions, and can cause lasting psychological benefits with one or two administrations. Supervised psychedelic sessions can reduce symptoms of anxiety, depression, and addiction, and improve well-being in healthy volunteers, for months or even years. But these benefits seem to be mediated by "mystical" experiences of cosmic consciousness, which prompts a philosophical concern: do psychedelics cause psychological benefits by inducing false or implausible beliefs about the metaphysical nature of reality?

This book is the first scholarly monograph in English devoted to the philosophical analysis of psychedelic drugs. Its central focus is the apparent conflict between the growing use of psychedelics in psychiatry and the philosophical worldview of naturalism.

Within the book, Letheby integrates empirical evidence and philosophical considerations in the service of a simple conclusion: this "Comforting Delusion Objection" to psychedelic therapy fails. While exotic metaphysical ideas do sometimes come up, they are not, on closer inspection, the central driver of change in psychedelic therapy. Psychedelics lead to lasting benefits by altering the sense of self, and changing how people relate to their own minds and lives-not by changing their beliefs about the ultimate nature of reality. The upshot is that a traditional conception of psychedelics as agents of insight and spirituality can be reconciled with naturalism (the philosophical position that the natural world is all there is). Controlled psychedelic use can lead to genuine forms of knowledge gain and spiritual growth-even if no Cosmic Consciousness or transcendent divine Reality exists.

Philosophy of Psychedelics is an indispensable guide to the literature for researchers already engaged in the field of psychedelic psychiatry, and for researchers-especially philosophers-who want to become acquainted with this increasingly topical field.

Introduction
Introduction
On the need for a natural philosophy of psychedelics
Introduction
The psychedelic renaissance
Evidence for safety and efficacy
An existential medicine?
The Comforting Delusion Objection
Naturalizing the entheogenic conception
The phenomenology of psychedelic therapy
Introduction
Perception
The sense of self
The transformative process
Conclusion
The mechanisms of psychedelic therapy
Introduction
Neuroplasticity theories
The Metaphysical Belief Theory
The Metaphysical Alief Theory
Conclusion
The role of self-representation
Introduction
Psychological factors
Neural correlates
Neurocognitive explanation
Conclusion
Resetting the brain
Introduction
The Reset Theory
Predictive processing
Relaxed beliefs under psychedelics
Resetting beliefs under psychedelics
Unbinding the self
Introduction
Predictive self-binding
Selfhood embodied and (temporally) extended
A centre of representational gravity
The self unbound
Opacity and mystical epiphanies
Psychedelic therapy: a two-factor theory
Self and self-consciousness
Conclusion
Epistemology
Introduction
Psychopharmacology and epistemology
Knowledge that
Knowledge how
Knowledge by acquaintance
New knowledge of old facts
Indirect epistemic benefits
Epistemic innocence
Spirituality
Introduction
Naturalizing spirituality
Spirituality as unselfing
Conclusion
Testable predictions
Future directions
Naturalistic entheogenics

Dr Chris Letheby , Lecturer in Philosophy, University of Western Australia

Dr Chris Letheby is a philosopher working on issues related to the therapeutic and transformative potential of classic psychedelic drugs. His doctoral research, conducted at the University of Adelaide, presented the first systematic analysis of psychedelic experience within the framework of 21st century philosophy of cognitive science. He is currently Lecturer in Philosophy at the University of Western Australia and Postdoctoral Researcher at the University of Adelaide on the Australian government-funded project 'Philosophical Perspectives on Psychedelic Psychiatry'. He was awarded an Early Career Researcher Prize in 2022 from the School of Humanities, University of Adelaide for this book. In addition he received the Faculty of Arts Prize for Outstanding Research by an Early Career Researcher, from the University of Adelaide.

`This excellent, well-argued, book is required reading for anyone with interests in philosophy of mind, philosophy of psychology, and philosophy of psychiatry. It presents the first book-length argument for the effectiveness of psychedelic therapy and provides an account of how this effectiveness may be understood from within cognitive neuroscience. Everyone should read this book! ' Richard Brown, Humanities Department, LaGuardia Community College, CUNY & M.S. program in Cognitive Neuroscience at the Graduate Center, CUNY

`'Philosophy of Psychedelics' is really two books in one. It provides an easily understood, scholarly and detailed review of psychedelic science, spanning phenomenology, psychology, neuroscience, and medical therapeutics. But setting this book apart from other recent books in this rapidly emerging field of inquiry, Chris Letheby takes his philosopher's scalpel to addressing intriguing philosophical implications of psychedelic research including the unsettling question of whether the claimed benefits from psychedelic experiences require the induction of delusional beliefs. This very readable volume should be of interest to scientists, philosophers, as well as those simply curious about the recent renaissance in psychedelic science and therapeutics. ' Roland R. Griffiths, Ph.D. Director, Center for Psychedelic and Consciousness Research, Professor, Departments of Psychiatry and Neuroscience, Johns Hopkins University School of Medicine

`'Philosophy of Psychedelics' is a terrific, intellectually meticulous study of the nature, meaning, and effects of psychedelic experiences. The discussion ranges over the mind-brain relation, transformative experiences, the ethics of psychedelic therapy, and whether psychedelics help us to see the nature of things as they really are or just produce uplifting and therapeutically positive hallucinations. Chris Letheby is a wise and careful guide to the current state of psychedelic therapy and sets very high standards for philosophers who want to follow him in thinking responsibly about this intriguing area of research. ' Owen Flanagan is James B. Duke Professor of Philosophy at Duke University, and the author of 'How to Do Things with Emotions' Princeton 2021