Neuroscience of Consciousness
January 1, 2017
Chris Letheby, Philip Gerrans
280 citations
Psychedelic-induced ego dissolution—where the sense of being a distinct self disappears—is best explained by predictive processing models of self-awareness. Self-awareness arises from hierarchical predictive models that posit a stable, enduring entity to which representations are bound. The self-model functions as a useful Cartesian fiction: a false representation of a simple substance that integrates cognitive processing across levels and domains. Unlike narrative accounts, this self-model has a robust cognitive function, but it does not qualify as a real self. Ego dissolution reveals the self-model's binding role in cognition, yet the self itself does not exist.
Scientific reports
November 23, 2021
Christopher Timmermann, Hannes Kettner, Chris Letheby et al.
208 citations
People who use psychedelic drugs often shift away from materialist views of reality and consciousness toward panpsychism and fatalism, with most changes lasting at least six months. In a large prospective online survey, these belief shifts correlated with greater past psychedelic use and improved mental health. Emotional synchrony with others during the experience mediated the changes, and baseline impressionability moderated them. An independent clinical trial confirmed the direction of belief change, suggesting psychedelics may causally influence metaphysical beliefs away from hard materialism, though contextual independence remains uncertain.
Consciousness and cognition
January 1, 2016
Chris Letheby
68 citations
The concept of 'epistemic innocence' holds that some flawed cognitive processes can still provide valuable knowledge otherwise unavailable. This idea is applied to psychedelic drugs, often dismissed as epistemically harmful due to their label 'hallucinogens'. The argument is that certain psychedelic states can be epistemically innocent, offering unique epistemic benefits despite their suboptimal nature. This conclusion has implications for psychedelic therapy policy and also refines the concept of epistemic innocence itself.
Journal of Psychedelic Studies
January 21, 2022
Chris Letheby, Jaipreet Mattu
19 citations
Serotonergic psychedelics have prompted philosophical questions that academic philosophers are now beginning to explore. This paper reviews four emerging research areas: selfless consciousness, psychedelic epistemology, psychedelic ethics, and spiritual or religious naturalism. It highlights questions about how psychedelics affect self-consciousness and phenomenal consciousness, the epistemic nature of psychedelic experiences, ethical issues surrounding appropriate use, and whether spiritual or religious aspects of psychedelic use can fit within a naturalistic worldview.
Philosophy and the Mind Sciences
March 24, 2020
Chris Letheby
18 citations
The paper challenges the widely held view that phenomenal consciousness always requires some form of self-consciousness, a principle called the subjectivity principle (SP). Previous defenses of SP argued that mental states lacking self-consciousness, such as inserted thoughts in schizophrenia or depersonalization experiences, are not genuinely conscious. The author presents ego-dissolution experiences induced by fast-acting serotonergic psychedelics as counterexamples that are both phenomenally conscious and entirely selfless. The paper then critiques the concept of "for-me-ness," a proposed minimal form of self-awareness, by posing a dilemma: if for-me-ness includes an experiential component, it is absent in these psychedelic states; if it does not, the definition undermines its proponents' claims and concedes that conscious states can lack self-consciousness. The conclusion reflects on the intuitive appeal of SP in light of altered-state evidence.
Zygon®
August 18, 2017
Chris Letheby
18 citations
A pressing philosophical problem is how to respond to existential anxiety and disenchantment arising from a naturalistic worldview that rejects transcendent foundations for meaning. The popularization of neuroscience makes this disenchanted view of humans more vivid and widespread. The study of transformative experiences from classic psychedelics like LSD and psilocybin may reveal a practical solution. Although psychedelic transformation often involves nonnaturalistic metaphysical beliefs, research suggests key elements of psychedelic spirituality are consistent with naturalism. These include disruption of neurocognitive mechanisms underpinning the sense of self, leading to self-transcendence and decoupling of attention from personal concerns, which can broaden perspectives and foster wonder and appreciation for life.
Philosophical Psychology
March 29, 2022
Nin Kirkham, Chris Letheby
15 citations
Classic psychedelic drugs, when administered safely in controlled settings, can induce vivid experiences of unity and connectedness that durably increase feelings of nature-relatedness and pro-environmental behaviors. This makes them a promising form of moral bio-enhancement for cultivating environmental virtues, particularly the master virtue of living in place, which encompasses respect for nature, proper humility, and aesthetic wonder and awe. The proposal offers a practical approach to changing individual behavior to address environmental challenges, which are often framed as collective action problems but also require individual change.
Neuroethics
May 17, 2024
Chris Letheby
14 citations
Psychedelic experiences can reduce fear of death, but this paper argues they do so mainly by promoting non-physicalist metaphysical beliefs, not by other proposed mechanisms. This supports the REBUS model of psychedelic therapy over alternatives. The finding also undermines the neuroexistentialist project of using psychedelics to naturalize spirituality: rather than reconciling people to a naturalistic worldview, psychedelics reduce existential angst by persuading people that such a worldview is false.
September 13, 2024
Chris Letheby, Philip Gerrans
6 citations
A recent wave of research re-examines classic psychedelic substances such as psilocybin, LSD, and DMT. Evidence suggests these can be given safely in controlled conditions at moderate to high doses and may help treat addictive and mood disorders. The main mechanism appears to be inducing a dramatically altered state of consciousness, but how psychedelic-assisted psychotherapy works and the relations between subjective experiences and neural changes are debated. This volume collects philosophical chapters on three themes: what psychedelic science reveals about self and mind; methodological, theoretical, and clinical questions about studying and using psychedelics therapeutically; and broader ethical, spiritual, and cultural implications of psychedelic experience.
Philosophy and the Mind Sciences
April 19, 2022
Chris Letheby
6 citations
The author defends two central claims from their book Philosophy of Psychedelics: that psychedelic therapy works mainly by altering mental representations of the self, and that it yields epistemic benefits compatible with a naturalistic worldview. In response to commentaries, the author agrees with some supplementary mechanistic points from Hoffman and from Martin and Sterzer, while offering qualifications. The author also engages with challenges from Lyon, Farrenikova, and Colombo, defending core commitments. On epistemology, the author endorses connections to agency-first epistemology and self know-how from Bortolotti and Murphy-Hollies, and engages with Caporuscio's concept of self-shaping, again with qualifications. Finally, the author is sympathetic to Fink's proposal that the main epistemic benefit is increased understanding, but criticizes arguments for Psychedelic Justification Impossibilism.
Philosophy and the Mind Sciences
April 19, 2022
Chris Letheby
3 citations
A book-length philosophical examination of classic psychedelic drugs like psilocybin and LSD addresses the Comforting Delusion Objection—the concern that psychedelic therapy relies on inducing non-naturalistic metaphysical beliefs, making it epistemically and ethically problematic. The book reviews evidence for therapeutic efficacy and argues that psychedelics work not by neuroplasticity alone or by inducing supernatural ideations, but by altering mental representations of the self. Drawing on predictive processing theory and the self-binding theory of self-representation, it proposes a speculative account of this mechanism. The final chapters argue that psychedelic therapy can yield epistemic and spiritual benefits compatible with a naturalistic worldview.
Routledge Handbook on the Philosophy of Meditation
January 1, 2022
Chris Letheby
2 citations
Psychedelics and meditation share deeper commonalities beyond altering consciousness. Recent empirical studies show both modulate overlapping brain networks involved in the sense of self, salience, and attention, and psychedelics can occasion lasting increases in mindfulness-related capacities for taking a non-reactive stance on inner experience. The self-binding theory of psychedelic ego dissolution explains these findings: by disrupting self-related beliefs in high-level cortical networks, both methods can unbind mental contents from one's self-model, moving them from phenomenal transparency to opacity. This weakens foundational beliefs about identity, allowing disidentification with these beliefs as "just thoughts." These connections may help consider epistemic benefits of meditation from a naturalistic perspective.
Philosophy of Psychedelics
August 1, 2021
Chris Letheby
2 citations
Three theories of psychedelic therapy are critically examined. The Molecular Neuroplasticity Theory, which attributes benefits to a drug-driven molecular process independent of conscious experience, is weakened by evidence that mystical-type experiences correlate with positive outcomes, indicating psychological mechanisms are involved. The Metaphysical Belief Theory and Metaphysical Alief Theory better account for this correlation by positing that a transcendent 'Joyous Cosmology' encountered during the experience drives change. However, these theories fail to explain why patients can meet psychometric criteria for a mystical-type experience without having a non-naturalistic metaphysical hallucination; more naturalistic experiences of ego dissolution and connectedness can also satisfy those criteria. The argument concludes that lasting benefits arise from a genuine psychological factor that correlates with mystical-type experience but is independent of non-naturalistic metaphysical ideations.
Philosophical Perspectives on Psychedelic Psychiatry
September 13, 2024
Chris Letheby, Philip Gerrans
1 citation
This chapter reviews the history of psychedelics in psychiatry, including the phenomenological and behavioral effects that initially prompted their therapeutic study. It provides an overview of recent research on the safety, efficacy, and therapeutic mechanisms of psychedelic-assisted psychotherapy. The chapter also summarizes the contributions of each chapter in the volume, showing how they address philosophical issues arising from the new wave of psychedelic psychiatry. The chapters are organized around three themes: 'Self and Mind', 'Science and Psychiatry', and 'Ethics and Spirituality'.
Journal of Psychedelic Studies
June 23, 2022
Shevaugn Johnson, Chris Letheby
1 citation
Psychedelic-assisted psychotherapy should be investigated as a treatment for body dysmorphic disorder (BDD). BDD involves appearance-based preoccupations and compulsions. Although existing treatments are safe and effective, non-response and relapse rates remain high. Preliminary evidence indicates safety, feasibility, and potential efficacy of psychedelic treatments for disorders sharing psychopathological mechanisms with BDD. Based on this evidence, qualitative reports, and theoretical proposals, the authors argue for a phase 2a study to assess safety and feasibility of psychedelic-assisted psychotherapy in BDD, and offer suggestions for future research.
Philosophy of Psychedelics
August 1, 2021
Chris Letheby
1 citation
Psychedelic research supports the view that transformative experiences and practices can legitimately be called 'spiritual' while remaining compatible with a naturalistic worldview. The existential transformation from some psychedelic experiences—temporarily suspending the default, self-referential mode of cognition and enabling feelings of connectedness, wonder, and awe—provides a paradigm for naturalistic spirituality. This evidence reinforces core ideas from recent philosophical work, such as spirituality being about connection, aspiration, and asking the Big Questions, and that these experiences overcome limitations of the ordinary sense of self. The chapter argues that such experiences and practices are independent of non-naturalistic metaphysical beliefs.
Philosophy of Psychedelics
August 1, 2021
Chris Letheby
1 citation
A single or a few controlled psychedelic experiences can durably reduce symptoms of anxiety, depression, and addiction, and produce lasting psychological benefits in healthy people. These effects appear to be mediated by 'mystical-type' experiences, which raises the Comforting Delusion Objection: if the benefits stem from an illusory experience, is the therapy epistemically problematic? Existing responses reject philosophical naturalism or downplay epistemic factors in psychiatric treatment, but both approaches face problems. The chapter outlines a new response showing the Objection fails even if naturalism is true and epistemic status matters.
Philosophy of Psychedelics
August 1, 2021
Chris Letheby
1 citation
Psychedelic therapy in controlled settings, such as clinical trials and religious rituals, commonly produces changes in perception and sense of self. Patients sometimes report non-naturalistic metaphysical epiphanies about cosmic consciousness or a divine Reality, but more frequently emphasize psychological insight, beneficial changes to self-representation, intense and cathartic emotional experiences, and feelings of connectedness and acceptance. This qualitative evidence suggests that therapeutic effects may not be due entirely to inducing metaphysical ideations.
Oxford University Press eBooks
August 1, 2021
Chris Letheby
A philosophical monograph examines whether psychedelic therapy conflicts with naturalism—the view that only the natural world exists. The book reviews evidence that LSD and psilocybin, given safely in controlled settings, can reduce anxiety, depression, and addiction and improve well-being for months or years, often through 'mystical' experiences. This raises a concern: Do psychedelics work by inducing false metaphysical beliefs? The author concludes this 'Comforting Delusion Objection' fails. Exotic metaphysical ideas arise but are not the main driver of change; instead, psychedelics alter the sense of self and one's relationship to their mind. Controlled psychedelic use can yield genuine knowledge and spiritual growth within a naturalistic framework.
Philosophy of Psychedelics
August 1, 2021
Chris Letheby
Psychedelic therapy works by 'unbinding' the self-model, according to the predictive self-binding account. In pathological conditions, rigid self-models become entrenched. Psychedelics induce neural and psychological plasticity, allowing experiences of ego dissolution and insight that enable revision of these maladaptive self-models. The therapy has a two-factor structure: induction of plasticity followed by discovery and consolidation of new self-modelling. This account subsumes mechanisms like feelings of connectedness, acceptance, psychological insight, emotional breakthrough, and mindfulness. The chapter also touches on philosophical questions about self and self-consciousness.
Philosophy of Psychedelics
August 1, 2021
Chris Letheby
Psychedelic therapy works primarily by disrupting and revising mental representations of the self. Three lines of evidence support this hypothesis: psychological insight during therapy, which is often autobiographical, correlates with positive outcomes; psychedelics enhance mindfulness capacities for an open, non-reactive attentional stance toward inner experience, which involves changes in the sense of self; and positive clinical outcomes are linked to changes in the Default Mode and Salience networks, both implicated in self-representation. These findings can be integrated into a cohesive account by considering the cognitive functions of the neural systems affected by psychedelics.
Philosophy of Psychedelics
August 1, 2021
Chris Letheby
Psychedelics may help treat mental disorders by disrupting large-scale neural networks stuck in dysfunctional configurations, allowing them to reset into healthier states. This chapter argues that this neural resetting hypothesis is correct but incomplete; it must be supplemented by an account of the cognitive functions of those networks. The predictive processing theory of cognition, which describes the brain as minimizing prediction errors, provides this account. One theory holds that psychedelics target networks encoding high-level beliefs, and disrupting these beliefs enables revision. The chapter proposes that the beliefs most often revised in successful psychedelic therapy are self-related beliefs.
Philosophy of Psychedelics
August 1, 2021
Chris Letheby
A book's concluding chapter recaps its main arguments and proposes future research directions. It provides a chapter-by-chapter summary of the book's arguments and lists testable predictions derived from them. It suggests further research in philosophy of science, philosophy of psychiatry, ethics, epistemology, and the philosophy of transformative experience. The chapter reflects on two central theses: that the Comforting Delusion Objection to psychedelic therapy fails, and that an 'Entheogenic Conception' of psychedelics as agents of epistemic benefit and spiritual experience is both consistent with naturalism and plausible given current evidence.
Philosophy of Psychedelics
August 1, 2021
Chris Letheby
Controlled psychedelic administration can yield epistemic benefits within a naturalistic framework. Insights into one's previously unknown mental states are probably often accurate but require sober scrutiny. Psychedelics offer knowledge by acquaintance with the mind's potential for diverse modes of attention and cognition, which can later be re-evoked, providing ability knowledge. They also facilitate new knowledge of old facts by making existing beliefs more vivid and motivating. Indirect epistemic benefits arise from psychological benefits, making therapeutic psychedelic experiences, in Lisa Bortolotti's terms, epistemically innocent.