21 April 2023

What Is Reality?

A Response to Chris Letheby

By John H. Buchanan, Ph.D.

MAPS Bulletin: Volume XXXIII Number 1 • 2023

I read with great interest Chris Letheby’s recent MAPS Bulletin article, “Philosophy of Psychedelic Therapy: Existential Medicine or Comforting Delusion” (Letheby, 2021b). By downplaying the metaphysical significance of psychedelic experiences, while at the same time affirming their psychological transformative power, Letheby offers a cogent defense of the psychotherapeutic use and benefit of psychedelics with an argument that is particularly effective for those who still ascribe to a conventional scientific worldview. To make this defense, however, Letheby relies upon scientific materialism for his philosophical touchstone and thereby undercuts some of the most important and interesting aspects of psychedelics for the journeyer. Obviously, this point of departure has significant implications for the interpretation of the kinds of extraordinary experiences that manifest under the influence of these substances.

More specifically, Letheby chooses to evaluate the reality of perceptions from psychedelic experience from the point of view of a physical or materialist “naturalism,” that is, from the belief “that the natural world studied by science is all that exists.” Not surprisingly, starting from a conception of the world as modern science understands it leads Letheby to the conclusion that “there is no cosmic consciousness, no spirit world, and no literally existing ‘disincarnate entities.’”¹ In the following, Letheby makes clear his reasons for working from this type of naturalistic standpoint: “First, naturalism is a simpler, more parsimonious views (sic) than alternatives which posit another reality. Second, there is no compelling evidence that disembodied entities or cosmic minds exist.” He goes on to say that a naturalistic approach to these phenomena can explain “the many strange and striking features of psychedelic experience that often prompt non-naturalistic interpretations.” In the remainder of this essay, I will argue that a broader understanding of naturalism—such as the kind found in the writings of Alfred North Whitehead—can provide a more interesting, illuminating, and sympathetic way of thinking about psychedelic experiences and evaluating the implications of the phenomena they reveal.²

¹ Unless otherwise noted, all quotes by Letheby are from his MAPS Bulletin article. Letheby initially refers to his position as “philosophical” naturalism, but quickly qualifies
this designation.

² Alfred North Whitehead, 1861-1947, was a mathematician, logician, philosopher of nature and science, mathematical physicist, metaphysician, and more. Whitehead co- authored the Principia Mathematica, devised an alternative theory of relativity, and created a new philosophical paradigm that he called the philosophy of organism, more widely known as “process philosophy.this designation.

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My own psychedelic experiences brought up many questions concerning perception, consciousness, spirituality, and the nature of reality in general: what Letheby calls the “Big Questions.” Although these extraordinary experiences gave me a deep “acquaintance” (as Letheby might have it) with these matters, they did not divulge how to coordinate these unorthodox insights with a rational conception of science or with my knowledge of the world more generally, nor tell me where I might fit into this new universe that had been revealed—or at least glimpsed. So while I would agree with Letheby that, even without the benefit of a metaphysical realignment, psychedelic experiences are often able to provide comfort for the dying, healing for the psychically injured, and creative inspiration; I think that it is a mistake to write off too quickly the most challenging and exciting metaphysical, epistemological, and cosmological implications of these substances. Consequently, I am not in favor of using the lens of scientific naturalism as the criteria for judging the empirical status of anomalous phenomena, be they related to psychedelic experience, parapsychology, mystical revelation, or anything else that doesn’t fit neatly into the current scientific worldview. It is essential to distinguish between science as an enterprise and methodology versus scientific naturalism as a belief system or worldview: a worldview that spurns metaphysical speculation when, in fact, it rests precariously upon its own unacknowledged presuppositions about the nature of reality. In short, rather than attempting to explain anomalous experiences, scientific naturalism is often used to explain them away based on its underlying—and generally unexamined—assumptions about what is actually possible.

Naturalism, more broadly speaking, is the position that there are no supernatural interventions in the processes of the universe. Letheby’s more qualified version of naturalism—namely, physicalistic or scientific naturalism—would fall under what David Ray Griffin has characterized as Naturalism-SAM, that is, a naturalism based on sensationalism, atheism, and materialism (Griffin, 2014).³ This form of scientific naturalism assumes: a) that sensory perception is the only valid source of information about a world outside us; b) that there is no Holy Reality; and c) that bits of inanimate matter—that is, matter devoid of experience or spontaneity—are all that exist. According to this view, all activity in the world is the result of mechanical interaction between these unfeeling bits. This worldview originally arose out of the philosophical innovations of Descartes and Galileo, centered around a radical division between consciousness and matter. (It should be noted that this mechanistic model was seriously challenged by competing animistic theories that included action at a distance; however, Descartes’ philosophy won out in no small part because of being championed by the Church, who saw it as less of a threat to its authority; Griffin, 2004).⁴ Over time, human consciousness or experience (and God) came to play an ever-diminishing role, resulting finally in Naturalism-SAM, where human experience itself is explained away as epiphenomenal or as identical to the physical brain. This represents a rather surprising development, since human experience was the one thing Descartes claimed could not be doubted as being real. But it is not surprising that it has proven so difficult to account for consciousness and extraordinary experience within a system that has evolved explicitly to deny the existence of anything other than inanimate matter.

If the only reason for questioning Letheby’s adoption of a naturalistic physicalism was that it shines a harsh light on the possibility of taking certain psychedelic experiences as veridical (i.e., as providing accurate perceptions of reality or actuality), this would be a difficult case to make even for someone enthralled with their psychedelic visions. However, as David Griffin emphasizes, physicalistic or scientific naturalism (Naturalism-SAM) is also unable to coherently account for many of the most fundamental ways we understand the world to be (Griffin, 2001). David Hume made abundantly clear that given only the data from conscious sense perception we cannot ascertain the reality of causation, temporality, the past, or even the mathematical basis of the scientific endeavor itself. On the other hand, a richer understanding of the nature of the universe, like that found in Whitehead’s process philosophy, helps us not only to understand the genesis of extraordinary experiences but also to affirm the real existence and efficacy of the external world, the passage of time, and other central features that define the world in which we live.

This understanding of the deeply relational nature of reality holds crucial implications for transpersonal psychology. Along with receiving a pronounced flow of neural feelings, the momentary events of the human psyche are also capable of directly receiving immediate experiential impressions from other human psyches (offering a potential channel for true intuition and telepathy)…

In sharp contrast to Naturalism-SAM, Griffin advocates for Naturalism-PPP (PPP standing for prehension; panexperientialism; panentheism). Whereas a physicalistic naturalism relies solely on perception from the sensory organs for information about the world, the first corrective offered by Naturalism-PPP involves recognizing a more primary mode of perception, what in process philosophy is called “prehension.” Whitehead also refers to this more fundamental means of access to the universe as “perception in the mode of causal efficacy,” in contrast to the clear, conscious perception of sensory data that scientific naturalism takes as its primary source of contact with the world. According to process philosophy, conscious sense perception is a derivative or secondary form of experience, which arises out of and is dependent upon a more basic and direct contact with reality. Some phenomena displaying aspects of this more basic mode of perception include intuition, short-term memory, and bodily sensations and feelings, all of which seem to flow directly into conscious experience and all of which have an immediate sense of derivation from past events.

That brings us to Griffin’s second corrective to a naturalistic physicalism: supplanting mechanistic materialism with panexperientialism. Panexperientialism is similar to many forms of panpsychism, but with some crucial differences. Where panpsychism often runs into trouble—for good reason, I think—is by (at least) implying that everything possesses consciousness. In contrast, with a Whiteheadian panexperientialism, aggregates like cars, rocks, and carpets do not possess unified feeling, much less consciousness. The universe is envisioned more as an ocean of feeling than as a field of pure consciousness. A Whiteheadian panexperientialism more cautiously allocates (mostly nonconscious) experience or primitive feelings to all fundamental events or “actual occasions.” Experience is the basic stuff; it is generated out of the reception of past feeling/data being synthesized into a new subjective event. As Whitehead says, “The creatures are atomic”: actual occasions are momentary bursts of intensive integrations of feelings from past events. (Whitehead & Griffin, 1985). These subjective events form into more large-scale organisms—like molecules, cells, animals—which often have their own guiding central events, such as those constituting the human psyche. The brain-body relationship is addressed by imagining the feelings of the neural cellular processes being in rapid interaction with a series of the much more complex experiential events, “dominant occasions,” that constitute the ongoing life of the psyche.

One of the greatest highlights of Psychedelic Science 2010 was a banquet event to honor the lifetime achievements of chemist Alexander “Sasha” Shulgin, Ph.D., and his lifetime partner, author and psychologist Ann Shulgin. Sasha Shulgin became best known for rediscovering MDMA (which was first synthesized in 1912), discovered hundreds of novel psychedelics, and together with Ann, co-authored the groundbreaking books PiHKAL and TiHKAL. The Shulgin benefit banquet fittingly coincided with MAPS’ MDMA-assisted psychotherapy for PTSD research, which had successfully expanded that year.

³ See especially pages 5-6 of David Ray Griffin’s incisive book on this subject, Panentheism and Scientific Naturalism.

⁴ See pages 11-17 of David Ray Griffin’s, Two Great Truths: A New Synthesis of Scientific Naturalism and Christian Faith.

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It is important to note that each new event grasps or feels (“prehends”) every past event to at least some slight degree and is then felt by all future events. This understanding of the deeply relational nature of reality holds crucial implications for transpersonal psychology. Along with receiving a pronounced flow of neural feelings, the momentary events of the human psyche are also capable of directly receiving immediate experiential impressions from other human psyches (offering a potential channel for true intuition and telepathy), from other entities more generally (furnishing access to the colorful array of entities encountered in nonordinary states), from a Divine actuality (fostering mystical and religious experiences), as well as from the simpler feelings inherent to the momentary events constituting nature in its many guises (providing a basis for intuitions related to animism and paganism).

Griffin’s third corrective step is replacing atheism with panentheism. Once we have seen how, via prehensive perception, veridical mystical experiences become real possibilities within Naturalism-PPP, it becomes more reasonable to credit the mystical experiences appearing in psychedelic states—and found throughout history—with more evidential weight than Letheby is inclined to grant them. One helpful image for panentheism is to see God as the soul of the universe, and the universe as God’s body. But while God is in everything and everything is in God, God is not everything. Panentheism thus differs from most pantheisms in that all momentary occasions and entities have their own moments of actuality, which are then felt by God. And God’s momentary experiences of the universe flood back into each newly arising occasion. This process of flooding back into provides an experiential mode of access to God’s being and guidance, as well as for a wide range of mystical experiences.

A Whiteheadian understanding of the transformative power of extraordinary experience might focus on the interruption and reorganization of self-structures, as does Letheby’s analysis. However, a process approach would highlight an increased flow of feeling from the unconscious disrupting the psyche’s habitual patterning and canalization of consciousness. These heightened feelings from the depths help facilitate access to repressed memories, blocked emotions, metaphysical insights, and even the possibility of encounters with transpersonal dimensions and entities. This Whiteheadian approach attributes these changes to effects related to shifts in neurological processes along with real changes in experiential psychic events. Letheby writes that, “On a naturalist view of the type that I favour, conscious experiences are real, physical events that occur within the brain and participate in causal relations, just as much as action potentials and alpha oscillations.” (Letheby, 2021a). While I applaud the spirit behind this sentiment, the idea that psyche-level experiences can be derived from Letheby’s kind of physicalistic naturalism seems to me incoherent, for all of the reasons presented above. Neither the “binding problem”—that is, the unity of conscious experience—nor psychic causality, nor the fact that subjective experience is the primary reality we know, can be adequately addressed by simply ascribing them to mechanistic cognitive processes in neural structures; nor can a materialist approach provide a rational account reconciling the existence of human subjective experience in a world made up solely of insentient matter. To better understand these fundamental issues—and to take seriously the powerful metaphysical insights arising from extraordinary experience—we need to broaden and deepen our notion of naturalism along the lines suggested by the title of one of David Griffin’s books: through a Reenchantment Without Supernaturalism.

This understanding of the deeply relational nature of reality holds crucial implications for transpersonal psychology. Along with receiving a pronounced flow of neural feelings, the momentary events of the human psyche are also capable of directly receiving immediate experiential impressions from other human psyches (offering a potential channel for true intuition and telepathy)…


Griffin, D. R. (2001). Reenchantment without supernaturalism: A process philosophy of religion. Cornell University Press.

Griffin, D. R. (2004). Two great truths: A new synthesis of scientific naturalism and Christian faith (1st ed). Westminster John Knox Press.

Griffin, D. R. (2014). Panentheism and scientific naturalism: Rethinking evil, morality, religious experience, religious pluralism, and the academic study of religion. Process Century Press.

Letheby, C. (2021a). Philosophy of Psychedelics: International Perspectives in Philosophy and Psychiatry. Oxford University Press.

Letheby, C. (2021b, December 28). Philosophy of Psychedelic Therapy: Existential Medicine or Comforting Delusion? Multidisciplinary Association for Psychedelic Studies—MAPS. https:// maps.org/news/bulletin/philosophy-of-psychedelic-therapy-existential-medicine-or-comforting-delusion/

Whitehead, A. N., & Griffin, D. R. (1985). Process and reality: An essay in cosmology (Corr. ed). Free Press.

Whitehead, A. N., & Russell, B. (1910). Principia Mathematica (Vol. 1–3). University Press.

John Buchanan, Ph.D.

John Buchanan, Ph.D. received his master’s degree in humanistic/ transpersonal psychology from West Georgia College, and his doctorate from the Graduate Institute of the Liberal Arts at Emory University. He has been trained and certified as a Holotropic Breathwork practitioner by Stan and Christina Grof. Buchanan has contributed a number of book chapters on his continuing interests in process philosophy and transpersonal psychology, and in 2020 was co-editor on Rethinking Consciousness: Extraordinary Challenges for Contemporary Science. His most recent work, Processing Reality: Finding Meaning in Death, Psychedelics, and Sobriety, was published in October, 2022. Dr. Buchanan also serves as president of the Helios Foundation.