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. (shrink)

Users of psychedelic drugs often report that their sense of being a self or ‘I’ distinct from the rest of the world has diminished or altogether dissolved. Neuroscientific study of such ‘ego dissolution’ experiences offers a window onto the nature of self-awareness. We argue that ego dissolution is best explained by an account that explains self-awareness as resulting from the integrated functioning of hierarchical predictive models which posit the existence of a stable and unchanging entity to which representations are bound. (...) Combining recent work on the ‘integrative self' and the phenomenon of self-binding with predictive processing principles yields an explanation of ego dissolution according to which self-representation is a useful Cartesian fiction: an ultimately false representation of a simple and enduring substance to which attributes are bound which serves to integrate and unify cognitive processing across levels and domains. The self-model is not a mere narrative posit, as some have suggested; it has a more robust and ubiquitous cognitive function than that. But this does not mean, as others have claimed, that the self-model has the right attributes to qualify as a self. It performs some of the right kinds of functions, but it is not the right kind of entity. Ego dissolution experiences reveal that the self-model plays an important binding function in cognitive processing, but the self does not exist. (shrink)

The urgent need for solutions to critical environmental challenges is well attested, but often environmental problems are understood as fundamentally collective action problems. However, to solve to these problems, there is also a need to change individual behavior. Hence, there is a pressing need to inculcate in individuals the environmental virtues — virtues of character that relate to our environmental place in the world. We propose a way of meeting this need, by the judicious, safe, and controlled administration of “classic” (...) psychedelic drugs as a way to catalyze the development of environmental virtues – a form of moral bio-enhancement. Recent evidence shows that psychedelics can be given safely in controlled environments, and can induce vivid experiences of unity and connectedness. These experiences, in turn, can durably increase feelings of nature-relatedness and pro-environmental behaviors. Therefore, we argue that responsible psychedelic use can reliably catalyze the development of a key environmental virtue known as living in place. This is a “master environmental virtue” that subsumes the qualities of respect for nature, proper humility, and aesthetic wonder and awe. Our account advances the environmental virtues debate by introducing a relevant practical proposal, and advances the psychedelic moral enhancement debate by providing a much-needed conceptual framework. (shrink)

Psychedelic ingestion and meditative practice are both ancient methods for altering consciousness that became widely known in Western society in the second half of the 20th century. Do the similarities begin and end there, or do these methods – as many have claimed over the years – share some deeper common elements? In this chapter I take a neurophilosophical approach to this question and argue that there are, indeed, deeper commonalities. Recent empirical studies show that psychedelics and meditation modulate overlapping (...) brain networks involved in the sense of self, salience, and attention; moreover, psychedelics can occasion lasting increases in “mindfulness-related capacities” for taking a non-reactive stance on one’s inner experience (e.g. Sampedro et al. 2017). The self-binding theory of psychedelic ego dissolution (Letheby and Gerrans 2017) offers a plausible explanation of these findings: by disrupting self-related beliefs implemented in high-level cortical networks, both psychedelics and meditation can “unbind” mental contents from one’s self-model, moving these contents along the continuum from phenomenal transparency to opacity (cf. Metzinger 2003). In other words, both psychedelics and meditation can expose and weaken our foundational beliefs about our own identity, allowing us to disidentify with these beliefs and see them as “just thoughts”. There are connections between these ideas and recent arguments suggesting that psychedelic use may have epistemic benefits consistent with philosophical naturalism (Letheby 2015, 2016, 2019). I conclude with a proposal: these connections may help in thinking about the putative epistemic benefits of meditation practice from a naturalistic perspective. (shrink)

Several authors have recently suggested that classic psychedelics might be safe and effective agents of moral enhancement. This raises the question: can we learn anything interesting about the nature of moral experience from a close examination of transformative psychedelic experiences? The interdisciplinary enterprise of philosophical psychopathology attempts to learn about the structure and function of the “ordinary” mind by studying the radically altered mind. By analogy, in this chapter we argue that we can gain knowledge about the everyday moral life (...) by studying extraordinary experiences of altered moral cognition and experience. We focus on a specific class of cases: experiences of forgiveness induced by psychedelics. We argue that close attention to such experiences reveals the importance of thought/emotion coherence and dissonance in the moral life and vindicates some heterodox ideas about moral phenomenology and psychology. (shrink)

In this précis I summarise the main ideas of my book Philosophy of Psychedelics. The book discusses philosophical issues arising from the therapeutic use of “classic” psychedelic drugs such as psilocybin and LSD. The book is organised around what I call the Comforting Delusion Objection to psychedelic therapy: the concern that this novel and promising treatment relies essentially on the induction of non-naturalistic metaphysical beliefs, rendering it epistemically objectionable. I begin the précis by summarizing material from chapters two and three (...) of the book, which review evidence for the therapeutic efficacy of psychedelics, and the facts about their clinical use that prompt the Comforting Delusion Objection. I then summarize materials from chapters four and five of the book, which argue that psychedelic therapy works neither by experience-independent processes of neuroplasticity, nor by inducing non-naturalistic metaphysical ideations, but by altering mental representations of the self. Next, I summarise the specific, speculative account of how this might work that is developed in chapters six and seven of the book. This account is based on the predictive processing theory of brain function and the self-binding theory of self-representation. Chapters eight and nine of the book argue, on the basis of this account, that psychedelic therapy can have significant epistemic and spiritual benefits that are compatible with a naturalistic worldview. I summarize this material, and then, finally, the overall conclusions about psychedelic therapy drawn in the tenth and final chapter of the book. (shrink)

In this opinion piece we propose the investigation of psychedelic-assisted psychotherapy for the treatment of body dysmorphic disorder (BDD). BDD is a psychiatric disorder characterised by appearance-based preoccupations and accompanying compulsions. While safe and effective treatments for BDD exist, non-response and relapse rates remain high. Therefore, there is a need to investigate promising new treatment options for this highly debilitating condition. Preliminary evidence suggests safety, feasibility, and potential efficacy of psychedelic treatments in disorders that share similar psychopathological mechanisms with BDD. (...) Drawing on this evidence, as well as on relevant qualitative reports and theoretical proposals, we argue that it would be worthwhile to conduct a phase 2a study aimed at assessing the safety and feasibility of psychedelic-assisted psychotherapy in BDD. We also offer some suggestions for how future research ought to proceed. (shrink)

Recent scientific research suggests that altered states of consciousness induced by classic psychedelic drugs can cause durable psychological benefits in both healthy and patient populations. The phenomenon of ‘psychedelic transformation’ has many philosophically provocative aspects, not least of which is the claim commonly made by psychedelic subjects that their transformation is centrally due to some kind of learning or knowledge gain. Can psychedelic experiences really be a source of knowledge? From the vantage point of philosophical materialism or naturalism, a negative (...) answer is tempting because psychedelic subjects often claim drug-facilitated knowledge of non-natural, transcendent realities. This fact, combined with common conceptions of these drugs as ‘hallucinogenic’ or ‘psychotomimetic’, invites the conclusion that claims of epistemic benefit from psychedelic experience are uniformly false. However, several recent proposals have been made in the literature about naturalistically acceptable epistemic benefits that might arise from psychedelic use. In this chapter I review these proposals, classifying them in accordance with standard epistemological categories, and discuss the arguments for and against them. I also offer some suggestions for future research. (shrink)

“Classic”, serotonergic psychedelic drugs such as LSD and psilocybin are the objects of renewed attention in science and psychiatry. A recent spate of research has produced evidence that psychedelics might be safe and effective adjuncts to the treatment of mood and addictive disorders, agents of positive psychological change in healthy subjects, and valuable tools for studying the neural mechanisms of perception and cognition. This chapter surveys three philosophical debates that have arisen in response to this “renaissance” of psychedelic research. The (...) first concerns the mechanisms of psychedelic-assisted psychotherapy (“psychedelic therapy”): How, exactly, does psychedelic administration in controlled conditions cause lasting psychological benefits? The second concerns the implications of psychedelic research for the philosophy of mind: Does psychedelic evidence show that there can be conscious mental states lacking all forms of self-consciousness? The third concerns the epistemic status of the psychedelic state: Is it possible that certain kinds of knowledge, or other epistemic benefits, could be gained by undergoing a psychedelic experience? (shrink)

Serotonergic (or “classic”) psychedelics have struck many researchers as raising significant philosophical questions that, until recently, were largely unexplored by academic philosophers. This paper provides an overview of four emerging lines of research at the intersection of academic philosophy and psychedelic science that have gained considerable traction in the last decade: selfless consciousness, psychedelic epistemology, psychedelic ethics, and spiritual/religious naturalism. In this paper, we highlight philosophical questions concerning (i) psychedelics, self-consciousness, and phenomenal consciousness, (ii) the epistemic profile of the psychedelic (...) experience; (iii) ethical concerns about the appropriate use of psychedelics; and (iv) whether spiritual or religious dimensions of psychedelic use are compatible with a naturalistic worldview. (shrink)