‘Philosophy of Psychedelics’ Book Forum: Part Two

Evgenia Fotiou reviews Philosophy of Psychedelics (Oxford University Press, 2021) by Chris Letheby.

This is Part Two of a Book Forum on Philosophy of Psychedelics. The Forum consists of four reviews and a reflection from the author.

For Part One by Nathan Emmerich and Bryce Humphries, click here.

For Part Three by Nicolas Langlitz, click here.

For Part Four by Sandeep Nayak, click here.

For Part Five by Chris Letheby, click here.

Chris Letheby’s Philosophy of Psychedelics is a welcome addition to the increasing literature on psychedelics, which so far has few contributions from the humanities. Much of the research being conducted in recent years on the therapeutic benefits of psychedelics has found the predominance of mystical-type experiences among those who participate. Some of these experiences are of spiritual entities and encounters that as Letheby points out are not consistent with a naturalistic worldview. Naturalism is the philosophical position that the natural world is all there is. It also does not accept insights that are shared by many partakers of psychedelics, namely that the mind or consciousness is the bedrock of the universe or the existence of non-natural entities such as spirits.

The central goal of the book is to respond to what he calls the “Comforting Delusion Objection”, stemming from a question posed by Michael Pollan in his 2018 book How to Change Your Mind: “Is psychedelic therapy simply foisting a comforting delusion on the sick and dying?” In other words, do psychedelics provide comfort by causing delusional beliefs? Some scholars argue that the epistemic status of psychedelics is not as important as the fact that they seem to be helping people. Letheby argues that even if naturalism is true and the epistemic status of psychedelics matters, the Comforting Delusion Objection fails.

The book begins by establishing the relative safety of psychedelics as well as the psychological benefits that have been supported in the research of the last several years. Letheby shows that the efficacy of these drugs does not depend on dosage or frequency of administration, rather their benefits have been argued to be the result of a mystical-type experience that tends to be common among partakers. In some of the literature it has been argued that participants emerge with metaphysical beliefs from these experiences, specifically, a belief in a unified consciousness permeating the universe and belief in spiritual realities. It is this type of experience that has prompted some scholars to refer to psychedelics as “entheogens”. In the words of Huston Smith, “The basic message of the entheogens [is] that there is another Reality that puts this one in the shade” (2003, 133).

Letheby explores the tension between such claims and the naturalistic worldview, which is part of a larger debate within the emerging field of psychedelic science about how much importance should be placed on non-naturalistic claims or metaphysical beliefs. Some authors are arguing that the mystical should be separated from the science in psychedelic studies (Sanders and Zijlmans 2021), while others argue that mystical experiences are at the core of psychedelic experience. While Letheby argues that naturalism should be “assumed correct” because we “are likely to see its truthfulness”, in later chapters he lays out the epistemic benefits of psychedelic experiences that he indeed sees as consistent with naturalism.

After summarising the main findings of scientific research into the therapeutic effects of psychedelics, Letheby discusses the Comforting Delusion Objection before going into his response. In the rest of the book, he aims to show that the epistemic benefits of psychedelic therapy are greater than the epistemic risks. To do that, he shows that not all reports of psychedelic experience mention ‘cosmic consciousness’—a Divine Reality—or other metaphysical beliefs but rather reveal several other themes such as connectedness, mindfulness, embodiment, psychological insights, and emotional breakthroughs. These do not necessarily go hand in hand with non-naturalistic beliefs as several philosophers he discusses in the book have pointed out.

Thus, Letheby on the one hand makes a good case for the safety and therapeutic potential of psychedelics and on the other, he tries to distance the psychedelic experience from beliefs or states of mind that might be perceived as non-naturalistic or epistemically inaccurate. He also claims the ‘epistemic innocence’ of psychedelic experiences, meaning that although some may be imperfect cognitions, they nevertheless confer a significant epistemic benefit to the subject while at the same time there is no alternative cognition available that would deliver the same benefits without epistemic costs.

The preparation of the psychedelic tea ayahuasca in Peru. Photo taken by author.

Finally, he attempts to naturalize the ‘entheogenic conception’ which he defines as seeing “psychedelics as agents not only of epistemic benefit but also of authentic spiritual experience and transformation” (p. 196). He does this by arguing that the conception of psychedelics as agents of insight and spirituality does not contradict a naturalistic worldview. His last task in the book is to show how a view of psychedelics as agents that promote spirituality can be “understood and defended within a naturalistic framework” (p. 196). The main thrust of his argument is that the therapeutic effects of psychedelics are not due to the generation of mystical-type experiences or non-naturalistic beliefs but rather due to alterations in the sense of self or changes to self-representation. These can include acute psychological insights, increased mindfulness, and psychological flexibility and according to certain studies modulation of the default mode and salience neural systems. According to Letheby, a big part of this process is due to the rewiring or restructuring of the “predictive self” or the disintegration or dissolution of the individual self. What he means by this is how a person realizes during their psychedelic experiences that the self-model they had formed about themselves is just a construction and therefore malleable. People thus report gaining perspective and seeing themselves differently during the experience, replacing potential pathological self-models with new and healthier self-modeling or self-representation. This is consistent with the findings of my own research which are based on ethnographic data collected in the context of shamanic tourism in Peru, for which I interviewed Westerners participating in ayahuasca ceremonies in Peru (Fotiou 2020a). I found that one of the main motives that Westerns pursue ayahuasca experiences is self-transformation and my interlocutors have reported similar experiences and benefits as the ones described in Letheby’s book.

Although the role of culture is not explicitly discussed by Letheby, it needs to be acknowledged that the discussion in the book is from a Western perspective and only applies to psychedelic therapy in a Western context. If we included Indigenous uses of psychedelics in this discussion, making similar arguments would be problematic. To insist that psychedelic experiences are non-naturalistic and therefore epistemically false, would be to claim that the vast majority of Indigenous peoples that have used these substances suffer from delusions since their use is intricately connected with worldviews that include non-human persons such as spirits. From an anthropological perspective, which strives to understand the viewpoint of the “other,” such a conclusion would be unacceptable. Therefore, taking into account the cultural context of any practice or belief is important. The idea that culture and ideology affect and even shape the psychedelic experience has long been supported by anthropologists. In fact, psychedelics have often been used in Indigenous cultures to reaffirm cultural ideologies rather than challenge them. For example, these substances have been used in initiation and other rituals that reaffirm the cultural values of the group. The therapeutic use of psychedelics in the West seems to primarily challenge widely-held cultural constructs and ideologies.

In my own research on shamanic tourism, I found that “framing” was important in how the experience was perceived and discussed by participants (Fotiou 2020b). In other words, when an experience is framed by facilitators as spiritual, participants are more likely to perceive it as such. In addition, in my earlier work, I hypothesized that it is possible that people who ingest psychedelics share similar experiences which they then interpret based on previous experiences and cultural background (Fotiou 2010). Much of this has to do with previous experience with psychedelics as well as the ambiguity of the psychedelic experience itself. Shamans learn to navigate and interpret this ambiguity before arriving to a culturally-appropriate perspective, while less experienced Western participants will interpret it based on their cultural background, which is rife with very specific discourses about psychedelics, e.g., that they cause spiritual experiences or delusions—depending on who you ask.

The author with Peruvian shaman, Don Solon. Photo taken by author.

There is one more point from ethnography that I would like to bring into this discussion. Amazonian shamans who use ayahuasca not only train for years to learn to navigate and interpret their experiences, but they also make a distinction between visions that are true and visions that are false. They do not take all their experiences at face value and an important part of their training is to learn to distinguish between the two. This ability to discern is important for many reasons that I do not have space to discuss here. Suffice to say that shamans learn to distinguish between epistemically good and bad cognitions, and they shared with me that both are possible under the influence of ayahuasca.

I should add that Letheby does not seem to be oblivious to the influence of culture on the issues he discusses. He does argue for example that the current operational definitions of mystical-type experience are not specific to cosmic consciousness-type experiences. Instruments that have been widely used in the assessment of psychedelic experiences such as the Hood Mysticism Scale, the Mystical Experience Questionnaire and the Altered States of Consciousness questionnaires are much broader than that and include experiences that do not conflict with naturalism. Thus, it is entirely possible that certain cultural biases contribute to the proliferation of a certain discourse about the centrality of metaphysical experiences in psychedelic therapy.

Overall, the book touches upon some important questions in the field of psychedelic studies and should at least initiate some good scholarly discussions. My hope is that the issues it raises will inform what kinds of questions scientific inquiry asks about these important substances in the future. People who have had mystical experiences on psychedelics might find some of the arguments of the book unsettling; others might find comfort in the idea that the psychedelic experience does not have to be at odds with a naturalistic worldview. The author of this review remains agnostic.


Fotiou, Evgenia. 2010. “Encounters with Sorcery: An Ethnographer’s Account.” Anthropology and Humanism 35 (2): 192–203. https://doi.org/10.1111/j.1548-1409.2010.01066.x.

Fotiou, Evgenia. 2020a. “Shamanic Tourism in the Peruvian Lowlands: Critical and Ethical Considerations.” The Journal of Latin American and Caribbean Anthropology 25 (3): 374–96. https://doi.org/10.1111/jlca.12508.

Fotiou, Evgenia. 2020b. “The Importance of Ritual Discourse in Framing Ayahuasca Experiences in the Context of Shamanic Tourism.” Anthropology of Consciousness 31 (2): 223–44. https://doi.org/10.1111/anoc.12117.

Sanders, James W., and Josjan Zijlmans. 2021. “Moving Past Mysticism in Psychedelic Science.” ACS Pharmacology & Translational Science 4 (3): 1253–55. https://doi.org/10.1021/acsptsci.1c00097.

Smith, Huston. 2003. Cleansing the Doors of Perception: The Religious Significance of Entheogentic Plants and Chemicals. Boulder, Colo.: Sentient Publications.

Evgenia Fotiou is a cultural anthropologist researching Indigenous Knowledge Systems, which often encompass both medical and religious knowledge. Specifically, she looks at how these systems get appropriated and reimagined as they become globalized. She has a PhD in cultural anthropology and Latin American studies from the University of Wisconsin-Madison, where she completed doctoral research on Amazonian shamanism in Peru and its transformation through globalization and the formation of transnational tourist networks. Dr. Fotiou is an expert in medical anthropology, anthropology of religion, shamanism, Amazonian cultures, and gender and has taught courses on these subjects. Her current work urges scholars of all disciplines to reexamine assumptions about Indigenous knowledge systems and to engage meaningfully with non-western epistemologies.

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