Modeling Strawson's Thin Subjects Using Category Theory Anand Rangarajan (Computer/Information Science, University of Florida, Gainesville, FL ) C11
In recent years, we have argued that Strawson's thin subject--a subject of experience (SoE) which coheres and dissipates like a physical particle--is tailor made for solving the hard problem. A key issue in Cartesian dualism has always been the mismatch between the unchanging "thick" subject and the physical world. In sharp contrast to Cartesian thick subjects, a thin SoE can potentially be accommodated in an expanded physicalism because its limited spatio-temporal nature is much more in sync with physical events and even more crucially, with phenomenology. But, accommodated how? To first get a handle on how SoEs can lead us in a fundamentally new direction, consider the competing narratives of emergence and panpsychism. Emergence would have us believe that systems at a certain level of complexity are accompanied by experience. The details are rarely spelled out leaving intact the tacit commitment to complex systems. Panpsychism--after rejecting this view--wants us to accept that nature has interiors "all the way down" with pan proto-psychism perhaps being a feature of elementary particles. Neither approach has any space within itself for SoEs which are more akin to particles than systems (thereby repudiating emergence) and/or for these particles to be composites rather than elementary (thereby repudiating panpsychism). In fundamental physics, particles are related to fields via second quantization--the theory which explains how and when waves (or more technically, fields) act like particles--as opposed to first quantization wherein particles act like waves. The field-particle relation is well understood in theoretical physics with the standard model repeatedly leveraging it to produce fermionic and bosonic particles from their respective fields. But more formally--and this does not seem to be widely appreciated in consciousness circles--second quantization is merely an instance of a mapping between categories (as in category theory). What this suggests is that we should consider using category theory to model the relationship between (expanded) foundational physical structures and SoEs with the nature of the relationship deciding between competing philosophical doctrines such as epiphenomenalism, panpsychism, materialism, emergence, naturalistic dualism, platonism and holism. Since we cannot expect much familiarity with category theory, we first review its mathematical underpinnings with an eye toward consciousness studies. Category theory is basically a story about compositionality. If a mapping exists between "low-level" categories and "high-level" categories, the high-level categories can be seen as composites or wholes with law-like relationships to lower levels. Such mappings between categories are called functors. Similar to equivalence relations, we have the concept of the equivalence of categories in category theory. (A necessary condition for equivalence, for example, is the existence of inverse functors.) Armed with this vocabulary (while relying on the machinery), we suggest that SoEs form a category and that there exists a functorial relationship between SoEs and the (expanded) physical. To the best of our knowledge, this approach is new. It has the attractive feature of being a mathematical model, prior to competing interpretations which we argue is a needed development in consciousness studies.