Studies have shown that both serotonin and glutamate receptor systems play a crucial role in the mechanisms underlying drug-induced synesthesia. The specific nature of these mechanisms, however, continues to remain elusive. Here we propose two distinct hypotheses for how synesthesia triggered by hallucinogens in the serotonin-agonist family may occur. One hypothesis is that the drug-induced destabilization of thalamic projections via GABAergic neuronal circuits from sensory areas leads to a disruption of low-level, spontaneous integration of multisensory stimuli. This sort of integration (...) regularly occurs when spatial and temporal attributes match. Destabilization of feedback loops, however, can result in incongruent experiences or binding of random thalamus activation with sensory input in a particular sensory modality. The second hypothesis builds on embodied cognition, cases in which visual images of external stimuli activate task-related neural regions. On this proposal, binding processes that do not normally generate awareness become accessible to consciousness as a result of decreased attentional discrimination among incoming stimuli. (shrink)

Induced by intake of the psychedelic substances LSD, psilocybin, DMT and mescaline, psychedelic experiences have been extensively described by subjects as entailing a most unusual increase in the scope and quality of their consciousness. Accordingly, psychedelic experiences have been widely characterised as an “expansion of consciousness.” This article poses the following question, as yet unaddressed in contemporary philosophy and the tradition of phenomenology: to what exactly does “expansion of consciousness” refer as a general characterisation of psychedelic experiences, and what (...) role might attention play therein? On the basis of Aron Gurwitsch’s phenomenology of attention, the following thesis is presented: (a) “expansion of consciousness” refers to a particular restructuration of consciousness in psychedelic experiences. (b) This occurs by means of certain extreme transformations in direction, scope, mode and degree of attention. In order to explicate this thesis, the characteristic features of psychedelic experiences that pertain to expansion of consciousness and attention are first systematically identified from a survey of subject reports. Second, it is demonstrated that the few previous attempts to understand expansion of consciousness in terms of attention as a filter/reducing-valve, spotlight or zoom-lens each fail to explain how consciousness is structured in psychedelic experiences. Third, it is argued that psychedelic expansion of consciousness is a general restructuration of consciousness by means of extreme attentional transformations. In conclusion, brief consideration is given to the question of whether psychedelic expansion of consciousness can have epistemic and ethical value for life. (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)

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)