Thomas Metzinger Minimal Phenomenal Experience The ARAS-model theory: Steps toward a minimal model of conscious experience as such This manuscript provides a short summary of an interrelated set of ideas presented in my third Carnap Lecture, given on 9 March 2018 at the Ruhr-Universität in Bochum, Germany. The current manuscript is only for purposes of discussion, it will not be submitted to any peer- reviewed journal; but all comments, relevant phenomenological case-studies, and constructive criticism are welcome. Some parts of it, together with new material, will be submitted in 2019, to a new academic open-access journal titled Philosophy and the Mind Sciences edited by Sascha Fink, Wanja Wiese, and Jennifer Windt (see for example Dresler & T. Metzinger, in preparation; Gamma & T. Metzinger, forthcoming; T. Metzinger, 2019, submitted). A simple 80-minute video of the original talk with slides is electronically available. The current manuscript is a work in progress and part of a larger research project. 1. Introduction In 2009, Olaf Blanke and Thomas Metzinger asked two questions: What are the minimally sufficient conditions for the appearance of a phenomenal self, that is, the fundamental conscious experience of being someone? What are necessary conditions for self- consciousness in any type of system (Blanke & T. Metzinger, 2009, p. 7)? One of their results was that bodily agency is a causally enabling, but not a constitutive condition, for phenomenal selfhood (Blanke & T. Metzinger, 2009, p. 13). Blanke and Metzinger then introduced the concept of “minimal phenomenal selfhood” (MPS), the central defining features of which are, (i) a globalized form of identification with the body as a whole (as opposed to mere ownership for body parts), (ii) spatiotemporal self-location and (iii) a weak, geometrical first-person perspective (1PP). This paper develops a related strategy for “minimal phenomenal experience” (MPE; this term was originally introduced in Jennifer M. Windt, 2015). It will take not full-body illusions, but the specific phenomenology of “pure consciousness” in meditation as a new entry point. One assumption is that MPE lacks, (i) MPS or other forms of self-consciousness, (ii) time representation, and (iii) a spatial frame of reference. More generally, here it is not the global phenomenology of identifying with the body as a whole that constitutes the empirical starting point, but all reports in which subjects claim that they have actually had an experience of consciousness as such. Is there really something like the simplest form of conscious experience? If yes, what are minimally sufficient conditions for MPE in neurotypical humans, and what are necessary conditions for the experience of consciousness as such in any type of system? There are five reasons that make MPE interesting: It could be the common phenomenological denominator that is always present whenever there is conscious experience at all, however rich or limited; second, a concerted attempt to isolate this hypothetical common denominator could lead to interdisciplinary unification by connecting different domains and experimental approaches in a new way; third, by aiming at a minimal model explanation (cf. Section 2) we could arrive at an entirely new theoretical model of conscious experience itself, 2 providing us with a fresh perspective and possibly even a new understanding; fourth, the MPE-approach could lead to unification within philosophy of mind itself, by elevating comparative and transcultural philosophy of mind to a new and more systematic level; and finally, reports about “pure consciousness” experiences are a neglected empirical phenomenon worth studying in itself. If – as many traditional theories claim1 - a minimal form of phenomenal experience is present in all forms of phenomenal content and functionally underlies all types of conscious experience, then developing an evidence-based minimal model of MPE would amount to solving the problem of consciousness as such. We could use its neural correlate as a marker for consciousness (T. Metzinger, 2000). Let us call this assumption the “fundamentality constraint”: If there really is an all-pervading but mostly implicit kind of phenomenal character which can at times be made explicit and which underlies all other forms of phenomenal experience, then it follows that the minimally sufficient neural correlate of MPE must be functionally integrated with that of all other conscious states. Put differently, we would then expect “computational bridging principles” connecting information processing in the physical correlate of MPE with all other types of conscious experience. On the other hand, MPE would be the only form of phenomenal content that could in principle be functionally autonomous and perhaps sometimes appear in isolation. I do not endorse the fundamentality constraint at this point. It is an open empirical question if MPE exists and if it satisfies this constraint in neurotypical human beings. All I want to do point out at this stage is a) that the idea has rich precursors in Indian philosophy of mind, and b) that, if true, it would open a completely route for empirical research programs on consciousness. If this background assumption could be demonstrated to be true, then it could lead to theoretical unification both within empirical consciousness research and across disciplines by connecting different domains and experimental approaches in a new way. Second, a minimal model would also provide a novel and deeper understanding of consciousness because the specific “representational ideals” governing the construction, analysis, and evaluation of theoretical models under the proposed strategy of minimalist idealization provide us with a new and more parsimonious perspective on the target phenomenon (Weisberg, 2012; section 6.2). At the same time, solving the problem of pure awareness would also be of highest relevance for comparative and transcultural philosophy: “Pure consciousness” has played a significant role in non-Western philosophy of mind, in particular, Advaita Vedanta and Buddhist theories of mind (cf. section 4 and 5.2). Traditional philosophical claims about an “empty” or “contentless” form of experience raise a problem for the currently leading kind of theories about consciousness, namely Representationalism: If this conscious state is not about anything, then there is an experience that is not defined by its content; therefore, Representationalism would be false. Here, first steps towards an investigation of minimal phenomenal experience are provided together with a defence of Representationalism. Thus, on a purely metatheoretical level, a more fine-grained conceptual model of MPE would, by integrating existing philosophical theories across cultural contexts, possess great heuristic and innovative potential. 3 The central empirical hypothesis of this discussion paper is as follows: For neurotypical human beings, the minimal form of conscious experience is constituted by the content of a predictive model serving to control and regulate the global signal of the Ascending Reticular Arousal System (ARAS), which in turn determines the brain’s general level of activation. Specifically, the ARAS-signal plausibly is not only the strongest internal source of free energy (Friston, 2010), but at the same time it also mediates cortical arousal which has long been known to be the major causally enabling factor for the instantiation of phenomenal states. The ARAS- model theory says that on its most fundamental level, conscious experience is a model of the hidden cause of the ARAS-signal. However, as explained in sections 2 and 8.2, terms like “ARAS”, “ARAS-signal”, or “ARAS-model” are here used as placeholders, with each of them specifying a whole range of potential empirical research programs. On a conceptual level, the main claim of this paper is that what has sometimes been called “pure” consciousness – i.e., the hypothetical “essence” of phenomenal awareness as such – is really a statistical hypothesis, a non-conceptual representation, dynamically modelling the hidden cause of the ARAS-signal (see figure 10 on p. 32). It has an intentional object. “Pure” consciousness really is a representational state, but, interestingly, one that instantiates a unique type of phenomenal character which is typically described as “empty” or non- representational. Part of the idea is that carefully relating the traditional problem of pure consciousness to current work in philosophy of mind and computational neuroscience may give us a new entry point, a fresh perspective on the problem of consciousness. Therefore, one goal is to gain a deeper phenomenological understanding of what, over the centuries, has often been reported as “bare awareness” or “consciousness as such” (and also why it has often been falsely reported as lacking content). A second goal is to find out whether the philosophical problem of defining “minimal phenomenal experience” (MPE) can be approached by conceptually developing a novel multidimensional construct. We need a new and more fine-grained psychometric instrument targeting the experience of “pure” consciousness – which, in humans, is implemented by what was provisionally called the ARAS- model above. In addition, the ARAS-model theory is not simply another initiative towards a classical reductive explanation for the specific phenomenology of pure consciousness. The third epistemic goal behind the current proposal is to test a new explanatory strategy for the problem of