# Philosophy of Psychedelics  ## Metadata - Author: [[Letheby, Chris;]] - Full Title: Philosophy of Psychedelics - Category: #books - Summary: insert summary - My notes: - Document Tags: [[psychedelic aesthetics paper]] [[psychedelics paper]] - Summary: Psychedelics promote well-being by disrupting the sense of self, allowing patients to access new perspectives. This therapy is not dependent on changes to metaphysical beliefs. The central mechanism of psychedelic therapy is the disruption and revision of mental representations of the self. Changes to self-representation are the common factor that connects the therapeutic benefits of psychedelics. The predictive self-binding account suggests that psychedelic therapy involves the temporary disintegration and subsequent revision of predictive models of the self. - Source File: Philosophy of psychedelics by Chris Letheby Oxford University Press (2021).pdf ## LLM Chats ## NotebookLM ## LLM Audio ## Highlights > Further anatomical and physiological facts suggest that the DMN plays a pivotal role in our mental economy. Its main nodes are pivotal ‘hub’ regions with unusually high levels of metabolic activity and anatomical connectivity. Evidence suggests that these hubs are involved in regulating or ‘tuning’ the activity and connectivity profiles of multiple far-flung neurocognitive systems throughout the brain ([Leech et al. 2012](#med-9780198843122-bibliography-1-bibItem-315), [Braga et al. 2013](#med-9780198843122-bibliography-1-bibItem-56), [Leech and Sharp 2014](#med-9780198843122-bibliography-1-bibItem-316)). Relevantly to our concerns, abnormal activity and connectivity of DMN hubs have been documented in multiple psychiatric pathologies ([Broyd et al. 2009](#med-9780198843122-bibliography-1-bibItem-621), [Whitfield-Gabrieli and Ford 2012](#med-9780198843122-bibliography-1-bibItem-582)). The activity and connectivity of these regions is also altered by meditation practices ([Fox et al. 2016](#med-9780198843122-bibliography-1-bibItem-164)). Notably, these regions are unusually rich in the 5-HT2A receptors that are psychedelics’ main molecular target ([Carhart-Harris et al. 2014](#med-9780198843122-bibliography-1-bibItem-72)). ([View Highlight](https://read.readwise.io/read/01jjgvz35zygt7tabt9w2btx6v)) - Tags: [[psychedelic aesthetics paper]] > As well as acute changes to the sense of self, modulation of the DMN has been linked to acute experiences of *insightfulness*. In the only neuroimaging study that I am aware of to probe the correlates of this specific psychedelic-induced experience, [Kometer et al. (2015)](#med-9780198843122-bibliography-1-bibItem-292) conducted electroencephalography (EEG) studies of healthy volunteers who received psilocybin or placebo, and quantified their subjective experiences using the 11D-ASC. Scores on the Insightfulness and Spiritual Experience sub-scales correlated strongly with lagged phase synchronisation of neuronal oscillations in the delta frequency band (1.5–4 Hz.) within a network comprising the parahippocampal cortex (PHC), the retrosplenial cortex (RSC), and the lateral orbitofrontal cortex. The RSC and the adjacent PCC are sometimes jointly described as the ‘posterior DMN’ ([Kaboodvand et al. 2018](#med-9780198843122-bibliography-1-bibItem-282), p. 2020). Moreover, the RSC and the PHC have both been hypothesised to facilitate information flow between cortical DMN nodes and memory-related structures in the medial temporal lobes, such as the hippocampus ([Ward et al. 2014](#med-9780198843122-bibliography-1-bibItem-572), [Kaboodvand et al. 2018](#med-9780198843122-bibliography-1-bibItem-282)). As Kometer et al. put it: ([View Highlight](https://read.readwise.io/read/01jjgw0v8wb6c8mvb54ajpj3p3)) - Tags: [[psychedelic aesthetics paper]] > Of course, the idea that psilocybin-induced insightfulness is associated with ‘increased retrieval and reattribution of autobiographic memories’ fits well with many of the items on the PIQ developed by [Davis et al. (2020)](#med-9780198843122-bibliography-1-bibItem-114) and discussed in [section 5.2.1](#med-9780198843122-chapter-5-div2-9) above. ([View Highlight](https://read.readwise.io/read/01jjgw26v89pn6dxnkyahtbk8b)) - Tags: [[psychedelic aesthetics paper]] > As we saw in [section 5.2.2](#med-9780198843122-chapter-5-div2-10), [Sampedro et al. (2017)](#med-9780198843122-bibliography-1-bibItem-477) found that mindfulness-related capacities for non-judging were increased in healthy volunteers two months after a single dose of ayahuasca. They also conducted neuroimaging scans of their subjects before and after the psychedelic experience. They found reduced levels of multiple neurotransmitters in the PCC, as well as increased functional connectivity at rest between (a) the PCC and the ACC, and (b) the ACC and medial temporal lobe structures involved in memory and emotion (including the hippocampus, a subcortical DMN node, and the amygdala, a subcortical SN node). These reductions in neurotransmitter levels and increases in functional connectivity correlated with the sustained increases in non-judging. ([View Highlight](https://read.readwise.io/read/01jjgw36r85yhz72vqjc0zc48c)) > The predictive self-binding account invokes key principles from the predictive processing (PP) theory of cognition. According to PP, the brain is an inference engine that builds hierarchical models of the world and uses them to predict its future inputs. These models are updated on principles of error detection and correction. Lower levels model more concrete perceptual features over smaller spatiotemporal scales, whereas higher levels model increasingly abstract features over larger scales. Each level attempts to predict the activity in the level below, and cognitive processing is driven by the imperative to minimise upward-flowing prediction error. On this view, conscious experience is a ‘controlled hallucination’—an internal virtual reality or world-simulation created by this modelling process. However, the mental models that constitute the furniture of our experiential worlds are *transparent*, meaning that they cannot easily be recognised *as* models. Phenomenologically, it is as though self, body, and world are simply, immediately, and unquestionably present (Metzinger [2003](#med-9780198843122-bibliography-1-bibItem-354), [2014](#med-9780198843122-bibliography-1-bibItem-359)). ([View Highlight](https://read.readwise.io/read/01jk35y42pznpz4vs4nze0v523)) - Tags: [[psychedelic aesthetics paper]] > According to the REBUS model, the most important and distinctive effects of psychedelics, especially at high doses, result from the weakening or relaxation of abstract, domain-general beliefs that reside toward the highest levels of the brain’s hierarchical predictive models. These fundamental beliefs, or high-level *priors*, are implemented in multimodal association areas such as the cortical midline hubs of the DMN and SN. In sober waking cognition, they structure and constrain the process of probabilistic inference that generates our phenomenal models of reality. Pharmacological disruption to these networks decreases the brain’s confidence in these foundational hypotheses, leading to an ‘unconstrained’ mode of cognition. ([View Highlight](https://read.readwise.io/read/01jk3635n3eybvems66m797cfe)) > The transparency noted above arises partly from the fact that our conscious reality-models or world-simulations inherit a high degree of structure, coherence, and volition-independence from the actual world that they seek to emulate. As Antti [Revonsuo (2006)](#med-9780198843122-bibliography-1-bibItem-450) puts it, our brains give us a thoroughly realistic and convincing ‘out-of-brain experience’: an experience as of simply being immediately present in a real, objective, extracranial world. The simulatory nature of our conscious reality is difficult to take seriously, other than as a merely intellectual proposition. Most of the time we cannot easily regard the constituents of our experiential worlds as virtual entities, or as products of a modelling process. Phenomenologically speaking, they simply appear as reality, and we automatically regard them as such: transparency in action. ([View Highlight](https://read.readwise.io/read/01hqj6zaw0ec5ntfhnwxqyb0mk)) > To say that consciousness is transparent, in this sense, is to say that we do not experience our mental models of the world *as* models: it is as though we look ‘through’ them and see only the world itself. This property of *phenomenal transparency* has been defined in many different ways; here, I adopt the following simple definition given by Thomas Metzinger:[2](#med-9780198843122-chapter-6-note-30) ([View Highlight](https://read.readwise.io/read/01jjyb6yx2ff0b820bqfhbgbq5)) > ‘Transparency’ refers to a property of conscious representations, namely, that *they are not experienced as representations*. Therefore, the subject of experience feels as if [they are] in direct and immediate contact with [the] content [of the representations]. Transparent conscious representations create the phenomenology of naïve realism. An opaque phenomenal representation is one that is experienced as a representation, for example, in … lucid dreams. ([View Highlight](https://read.readwise.io/read/01jjyb71jm42sm8zrqeepraajr)) > According to PP and related views, this transparency is profoundly misleading ([Metzinger 2003](#med-9780198843122-bibliography-1-bibItem-354), [Revonsuo 2006](#med-9780198843122-bibliography-1-bibItem-450)). All the furniture of our waking experience—the people, animals, plants, tables, chairs, and our own bodies and selves—is as thoroughly virtual, internally constructed, and simulatory as the fantastic creations of nocturnal dreams and psychotic hallucinations. The main difference is that, in normal waking consciousness, the contents of the models that populate consciousness are strongly constrained (hence ‘*controlled* hallucination’) by complex streams of multimodal sensory inputs from the actual extracranial world. (PP as a theory of cognition only makes sense on the assumption that there *is* an external world whose structure the brain must track in order to guide adaptive behaviour.) ([View Highlight](https://read.readwise.io/read/01jjyb7a8n580rn0wv5c6rq4br)) > Conflicting inputs are dismissed as unreliable noise, and the perceptual model settled on by the brain represents the object in a manner that we know, intellectually, to be inaccurate. In such cases, it becomes obvious that the contents of experience are determined by a fallible sub-personal process of probabilistic inference. Our phenomenal representations become somewhat opaque: we can, unusually, experience them *as* representations—at least to an extent. (Perceptually, of course, the illusion persists, despite our metacognitive awareness of its true nature.) ([View Highlight](https://read.readwise.io/read/01jk40vb1xjmt3vfajfv03pqxq)) > The example of the Hollow Mask Illusion illustrates another central aspect of the PP scheme: the process of error-driven model updating requires the brain to estimate the relative *reliability* of both its prior expectations and its various input channels.[3](#med-9780198843122-chapter-6-note-31) In the Hollow Mask case, the prior assumption that faces are convex is assigned such a high probability that it outweighs sensory evidence to the contrary. Such evidence, no matter how persistent, is never deemed sufficiently trustworthy by the brain to override such a well-confirmed prior belief. Indeed, the sensory evidence is deemed untrustworthy precisely *because* it conflicts with such a deeply entrenched assumption. In such cases, sub-personal mechanisms in the predictive brain engage in something analogous to David Hume’s refusal to countenance reports of miracles *qua* violations of natural law, on the grounds that our evidence for the inviolability of natural laws is sufficiently strong to outweigh any possible testimonial evidence for their violation. ([View Highlight](https://read.readwise.io/read/01jk40yykbk4jykkq6qv14mzdn)) > Prior knowledge is enabling because, without predictive models, we could not perceive anything at all. Models are needed to extract the signal from the noise of our sparse and ambiguous sensory inputs, to impose coherence and structure on what would otherwise be a buzzing, blooming confusion. ([View Highlight](https://read.readwise.io/read/01jk40zvtcx7e240d9c4vtj2mb)) > On the PP scheme, the networks targeted by psychedelics implement the highest levels of the brain’s generative model. This is to say that, among other things, they encode our most abstract, fundamental beliefs about self and world—our bedrock, largely unconscious, domain-general assumptions concerning space, time, and causality, the laws of logic, and the existence of the self. Philosophers have repeatedly noted the existence and significance of these foundational beliefs. Riding roughshod over important subtleties, we might liken them to Kantian categories, to Wittgensteinian ‘hinge’ or ‘framework’ propositions, to the constituents of a Kuhnian paradigm, or to the central nodes of a Quinean web of belief. In ordinary cognition, these ‘hyperpriors’ play a crucial role in constraining the brain’s hypothesis space, drastically limiting the kinds of world-models that it can generate, and thereby making the process of probabilistic inference computationally tractable ([Swanson 2016](#med-9780198843122-bibliography-1-bibItem-541)). ([View Highlight](https://read.readwise.io/read/01jk410r7fwd8qfr0zkz2df48h)) > Interestingly, the *noetic quality*—the feeling of certainty or direct knowledge—might also result from a weakening of the sense of separate selfhood. The idea here is that the sense of being an entity distinct from the object of knowledge is a prerequisite for conceiving of the possibility of error: with no sense of a distinct knowing subject, there is no sense of a fallible epistemic connection between that subject and a distinct object of potential knowledge. Hence, doubt is inconceivable. This principle is illustrated clearly by Michael Pollan’s report of his 5-MeO-DMT experience, which we encountered in [Chapter 3](#med-9780198843122-chapter-3): ([View Highlight](https://read.readwise.io/read/01jk413xje0t5gjs73wtfdvgch)) > I felt a tremendous rush of energy fill my head … and then … ‘I’ was no more, blasted to a confetti cloud by an explosive force. I could no longer locate [myself] in my head, because it had exploded that too, expanding to become all that there was. Whatever this was, *it was not a hallucination. A hallucination implies a reality and a point of reference and an entity to have it. None of those things remained.* ([View Highlight](https://read.readwise.io/read/01jk414d6m4j78a3cfvh6cad76)) > By disrupting the neurocognitive substrates of the brain’s high-level beliefs, psychedelics can change this situation transiently but dramatically. They diminish the brain’s confidence in its deepest assumptions about reality, including about the self, and thereby weaken the influence of those beliefs on the contents of the phenomenal world. This has two important effects. First, subjects experience new phenomenal worlds inconsistent with, and previously precluded by, those beliefs. Second, as a corollary, the beliefs themselves become phenomenally *opaque* as their representational nature becomes vividly apparent. Through radically altered forms of self-experience, subjects discover the contingency, mutability, and simulatory nature of their own sense of identity and habitual modes of attention. They learn directly that there are other ways of being, and other ways of seeing, because their ordinary ways of being and seeing result from a malleable modelling process. ([View Highlight](https://read.readwise.io/read/01jk38rxra8rsyagzrjyxbbxy8)) - Tags: [[psychedelic aesthetics paper]] > The answer, in brief, is that when mental contents are unbound from the self-model they can attain a degree of *phenomenal opacity* that is closely related to mindfulness-related capacities and psychological flexibility. As we have seen, predictive models in general exhibit the property of phenomenal transparency: they are not experienced as models, but simply appear, phenomenologically, as reality itself. This applies at least equally to the self-model. The all-important substantial entity posited by the predictive brain does not appear to us as a model or a story. Rather, we experience it as nothing more or less than our own immediate, unproblematic existence. In Metzinger’s words: ([View Highlight](https://read.readwise.io/read/01jjpntvpb5f94c21vq1jyd5wn)) - Tags: [[psychedelic aesthetics paper]] > Indeed, Metzinger posits that transparency is a *defining* feature of a phenomenal self-model (PSM): to the extent that a cognitive system operates with an opaque model of its own functioning, it will not have the phenomenal experience of ‘being someone’, which can only result from the ‘naïve-realistic self-misunderstanding’ ([Metzinger 2003](#med-9780198843122-bibliography-1-bibItem-354), p. 333) involved in transparent self-modelling. This connects with an important observation from the phenomenology of mindfulness meditation: to see thoughts and feelings as *mere* thoughts and feelings is ipso facto to disidentify with them ([Albahari 2006](#med-9780198843122-bibliography-1-bibItem-8), pp. 63–64; cf. [Wright 2017](#med-9780198843122-bibliography-1-bibItem-590), p. 71, [Sierra-Siegert and Jay 2020](#med-9780198843122-bibliography-1-bibItem-509)). To the extent that elements of the self-model become phenomenally opaque, they no longer form part of a self-model proper, because they are experienced as objects in awareness, rather than as the subject who is aware of those objects. The induction of phenomenal opacity into mental models, especially self-models, has been described as a central aim of traditional Buddhist meditation practices ([Metzinger 2003](#med-9780198843122-bibliography-1-bibItem-354), p. 566, [Lutz et al. 2019](#med-9780198843122-bibliography-1-bibItem-330)). ([View Highlight](https://read.readwise.io/read/01jjgvcv4znsfh3tzz3eaybg9c)) > My suggestion is that it can go both ways. On one hand, rendering thoughts and feelings phenomenally opaque by watching them calmly and non-reactively in meditation, seeing them as ‘*just* thoughts and feelings’, can lead to disidentification with them. On the other hand, disidentification with such mental contents, induced by psychedelic unbinding of the self-model, can confer an ability to watch them non-reactively. By reducing the brain’s confidence in its hypotheses about who, what, and where ‘I’ am, the phenomenal unit of identification can be expanded, contracted, shifted, or rendered ambiguous, such that it no longer determinately includes many of the thoughts, feelings, and perspectives with which we usually identify. These mental contents can then enter an open, spacious, non-goal-directed attention in the phenomenal guise of *mere* thoughts and feelings. No longer identified with so strongly, they evoke less defensiveness and reactivity. And if the control of attention is itself decoupled from self-representation, then the normal motivations for avoiding, suppressing, or rationalising uncomfortable thoughts and feelings may not wield their usual influence. ([View Highlight](https://read.readwise.io/read/01jjgvd70fd9dtxje4nrhxh67e)) - Tags: [[psychedelic aesthetics paper]] ## New highlights added February 13, 2025 at 9:50 AM > While these foundational assumptions are deeply entrenched, the sub-personal process of probabilistic inference will never settle on a model of a spaceless, timeless, selfless, unitive world. It will never settle on a model of a world in which distinct objects stably occupy the same spatial position, or human faces are concave. ([View Highlight](https://read.readwise.io/read/01jkz7qpma8nvawsabsbz1y68w)) > With regard to their potential therapeutic use, we propose that psychedelics work to relax the precision weighting of pathologically overweighted priors underpinning various expressions of mental illness. We propose that this process entails an increased sensitization of high-level priors to bottom-up signaling … and that this heightened sensitivity enables the potential revision and deweighting of overweighted priors. ([View Highlight](https://read.readwise.io/read/01jkz7n50vmzte2gqs7ygqs4py)) ## New highlights added February 13, 2025 at 11:08 AM > Hyperpriors constrain cognition by deeming many logically possible (and, indeed, logically impossible) worlds so improbable that they become cognitively and phenomenologically impossible. By diminishing the brain’s confidence in its foundational axioms, psychedelics expand the phenomenological possibility space (cf. Metzinger [2003](#med-9780198843122-bibliography-1-bibItem-354), [2011](#med-9780198843122-bibliography-1-bibItem-356)). ([View Highlight](https://read.readwise.io/read/01jkzcb78tdx1rgvbqz6bkdpbd)) ## New highlights added February 17, 2025 at 7:43 PM > This weakens the constraining influence of those priors on the process of probabilistic inference, thereby expanding the space of phenomenologically possible worlds. We have seen, in brief outline, how this model might explain some key phenomenological features of the psychedelic state. But what does it have to tell us about the therapeutic mechanisms of psychedelics? ([View Highlight](https://read.readwise.io/read/01jmajg89hhrerpaqgd7etxmgb)) > Moreover, several other classes of high-level beliefs disrupted by psychedelics seem like poor candidates. It is hardly plausible, for instance, that patients’ mental health is improved by adopting new beliefs about the nature of space and time, or by rejecting the law of non-contradiction.[7](#med-9780198843122-chapter-6-note-35) ([View Highlight](https://read.readwise.io/read/01jmak6a90nd53pd2arhyp0e6y)) > [7](#n0895) I know of no evidence that dialetheists are, on average, more mentally healthy than monoletheists. ([View Highlight](https://read.readwise.io/read/01jmak5tb3r4r55me7b64qaf10)) ## New highlights added March 13, 2025 at 8:46 AM > Visual parables and metaphors constitute an alteration to perceptual experience, but also an experience of apparent *insight* (a phenomenon we will return to shortly): they engender novel understanding or comprehension, or at least feelings thereof. ([View Highlight](https://read.readwise.io/read/01jp75qkvmdrzt8qaj3yrdxe5w)) > Alan Watts went so far as to single out time dilation and ego dissolution as the two definitive effects of psychedelics: ‘there are certain types of change which are usual enough to be considered characteristic of psychedelics: the sense of slowed or arrested time, and the alteration of “ego boundary” ’ ([Watts 1964](#med-9780198843122-bibliography-1-bibItem-575)). An example of time dilation is provided by the British MP Christopher Mayhew, who took mescaline on live television: ([View Highlight](https://read.readwise.io/read/01jp7642rkg05bdaksk3ptdvg8)) > There were profound feelings of unity, first with a red tulip, and then with a rose of the same color. When looking at the rose as an object, it seemed to come alive before my eyes. Its petals seemed to breathe as, slowly and gracefully, they unfolded, seeming to express the ultimate in beauty. Fascinated, I watched these movements of cosmic gentleness until, suddenly, I *knew* the rose; that is to say, I somehow became One with the rose, no longer existing as an ego passively viewing an object in its environment. Although in the objectivity of my critical mind I knew there were no physical changes in the flower, subjectively I seemed to see it in a totally new perspective, one which elicited tears and deep feelings of reverence. The rose seemed to stand out in naked beauty, as though it were the only thing existing in the world. Supporting the ancient monistic school of thought, I expressed the philosophical insight that ‘we are all the same thing’. Once I sought to express my experience by speaking of ‘becoming one with the very essence of Roseness.’ Another time I commented that, ‘There is more to beauty than we know.’ ([View Highlight](https://read.readwise.io/read/01jp76d6py8qaksp4v9rvefdw9)) > Taken at face value, such reports seem to demonstrate clearly that there can, indeed, be ‘totally selfless’ states of consciousness (Millière 2020)—that is, phenomenally conscious mental states that completely lack any sense of self. However, the interpretation of such reports is controversial. I will return to these issues in [Chapter 7](#med-9780198843122-chapter-7). ([View Highlight](https://read.readwise.io/read/01jp77318rg8xz8wqpjrv82bxw)) > Another important point is that ego dissolution is not a monolithic affair, because self-consciousness is not monolithic. On a broad level, recent theoretical discussions recognise a distinction between ‘narrative’ and ‘minimal’ forms of self-awareness ([Gallagher 2000](#med-9780198843122-bibliography-1-bibItem-174), [Lou et al. 2017](#med-9780198843122-bibliography-1-bibItem-328)). Narrative self-awareness refers to the autobiographical sense of being a temporally extended entity with a specific history and personality, whereas minimal self-awareness refers to the bare feeling of being a subject of experience at a moment in time. On some accounts, minimal self-awareness arises from basic sensorimotor processes, particularly *interoceptive* processes that represent the internal condition of the body (Damasio 1999, [Seth 2013](#med-9780198843122-bibliography-1-bibItem-499)). ([View Highlight](https://read.readwise.io/read/01jp773kqm54x8zdw3mwzjdb73)) > Early clinical accounts of psychedelic states recognised this distinction, distinguishing the loss of ‘bodily ego feeling’ from the loss of ‘mental ego feeling’ under LSD ([Savage 1955](#med-9780198843122-bibliography-1-bibItem-482)). More recently, [Girn and Christoff (2018)](#med-9780198843122-bibliography-1-bibItem-191) have offered a more fine-grained (but non-exhaustive) taxonomy of aspects of self-consciousness affected by psychedelics. They include (i) the sense of ownership over the body and thoughts (feeling that *this is my body* or *this is my thought*), (ii) the sense of agency over actions and thoughts (feeling like the one who has initiated or authored the action or thought), (iii) the sense of self-location (the feeling of ‘being located at a particular point in space’), (iv) the minimal self (the bare feeling of being a subject of experience), (v) autobiographical or narrative self-awareness, (vi) body image and body representation, and (vii) the sense of bodily boundaries ([Girn and Christoff 2018](#med-9780198843122-bibliography-1-bibItem-191)p. 133; cf. Millière 2020). ([View Highlight](https://read.readwise.io/read/01jp7753gxce1kkbnjjva6qaqv))