Materialism/Philosophical—Overview

Materialism is the claim that consciousness is entirely physical, solely the product of biological brains, and all mental states can be fully “reduced” to, or wholly explained by, physical states—which, at their deepest levels, are the fields and particles of fundamental physics. In short, materialism, in its many forms and flavors, gives a completely physicalist account of phenomenal consciousness.

Empirical and Scientific Support

Overwhelmingly for scientists, materialism is the prevailing theory of consciousness. To them, the utter physicality of consciousness is an assumed premise, supported strongly by incontrovertible empirical evidence from neuroscience (e.g., brain impairment, brain stimulation). This is “Biological Naturalism,” as exemplified by philosopher John Searle (Searle, 2007a, 2007b). It is a view that, to a first approximation, promises, if not yet offers, a complete solution to Chalmers's hard problem.^[1]

To neuroscientist Susan Greenfield, the nonmaterialist view that consciousness might be irreducible is “‘a get-out-of-jail-for-free card,’ that is to say, whatever I did, whatever I showed you, whatever experiments I did, whatever theories I had in brain terms, you could always say ‘consciousness has the extra thing,’ and this extra thing is the thing that really counts and is something that we brain scientists can't touch.” She adds, “If reduction is a ‘dirty word,’ we can say ‘explicable,’ ‘interpretable,’ or ‘understandable,’” but explaining consciousness must always and solely be in brain and body terms (Greenfield, 2012).

Compared to some of the consciousness-as-primary theories that follow, Materialism Theories can be counted as deflationary (which doesn't make them wrong, of course, or even unexciting). To physicist Sean Carroll, consciousness is “a way of talking about the physical world, just like many other ways of talking. It's one of these emergent phenomena that we find is a useful way of packaging reality, so we say that someone is conscious of something that corresponds to certain physical actions in the real world.” Carroll is unambiguous: “I don't think that there is anything special about mental properties. I don't think there's any special mental realm of existence. I think it's all the physical world and all the manifold ways we have of describing it” (Carroll, 2016).

Nobel laureate biologist Gerald Edelman agrees. He does not consider the real existence of qualia to be an insurmountable impediment to a thoroughly materialistic theory of consciousness. “To expect that a theoretical explanation of consciousness can itself provide an observer with the experience of ‘the redness of red’ is to ignore just those phenotypic properties and life history that enable an individual animal to know what it is like to be such an animal. A scientific theory cannot presume to replicate the experience that it describes or explains; a theory to account for a hurricane is not a hurricane. A third-person description by a theorist of the qualia associated with wine tasting can, for example, take detailed account of the reported personal experiences of that theorist and his human subjects. It cannot, however, directly convey or induce qualia by description; to experience the discriminations of an individual, it is necessary to be that individual” (Edelman, 2003). While Edelman's honest assessment may give Materialism Theories their best shot, many remain unpersuaded. After all, still, we wonder: what are qualia? Literally, what are they!

Philosophical Positions

Even among philosophers, a majority are physicalists (but just barely). In their 2020 survey of professional philosophers, Bourget and Chalmers report 51.9% support Physicalism; 32.1%, Non-physicalism; and 15.9%, Other (Bourget & Chalmers, 2023, 2014).

Chalmers provides “roughly three ways that a materialist might resist the epistemic arguments” by mitigating the epistemic gap between the physical and phenomenal domains, where “each denies a certain sort of close epistemic relation between the domains: a relation involving what we can know, or conceive, or explain.” According to Chalmers, “A type-A materialist denies that there is the relevant sort of epistemic gap. A type-B materialist accepts that there is an unclosable epistemic gap, but denies that there is an ontological gap. And a type-C materialist accepts that there is a deep epistemic gap, but holds that it will eventually be closed” (Chalmers, 2003).

A subtle way to think about Materialism Theories recruits the concept of “supervenience” in that “the mental supervenes on the physical” such that there cannot be a change in the mental without there being a change in the physical. One such subtlety is the modal force of the connection or dependency, parsing among logical necessity, metaphysical necessity, factual or empirical necessity, as well as among explanation, entailment, grounding, reduction, emergence, ontological dependence, and the like. For this Landscape of explanations of consciousness, we leave “supervenience” to others (McLaughlin & Bennett, 2021).

Similarly, the relationship between introspection and consciousness is an intimate one, linking the epistemology of self-knowledge with the metaphysics of mind. For several theories of consciousness, introspection is essential (e.g., neurophenomenology), though for most, it is a non-issue (Smithies & Stoljar, 2012).

Scope and Subcategories

Two major theories of consciousness are Integrated Information Theory and Global Workspace Theory. Both are important, of course, and perhaps by situating them on the Landscape, they can be evaluated from different perspectives. In what may reflect my personal bias, I [RLK] situate Global Workspace Theory under Materialism's Neurobiological Theories, while Integrated Information Theory fits under Information as a separate category (where Information is the primary ontological reality, as opposed to information in the Computational/Functionalism subcategory under Materialism where information is descriptive but not ontologically fundamental). All of this reflects my sense of the nature of their mechanisms, not my opinion of the truth, or even relative truth, of their claims.

In also reflecting my personal sense, to understand consciousness at this point should not be limited to selected ways of thinking or knowing but should rather seek expansive yet rational diversity. Certainly, one can make assessments among and between theories, but to single out two, or five, or even 20, is, to me, a narrowing too soon.

I group Materialism Theories into thirteen subcategories: Philosophical Theories, Eliminitive/Illusionism Theories, Mind-Brain Identity Theories, Neurobiological Theories, Electromagnetic Field Theories, Computational and Informational Theories, Homeostatic and Affective Theories, Embodied and Enactive Theories, Relational Theories, First-Order Theories, Higher-Order Theories, Language Relationships, and Phylogenetic/Evolution Theories.

While many of the following theories under Materialism Theories proffer to explain what happens in consciousness, or what causes consciousness, in that they describe alternative critical processes in generating consciousness, the question always remains, are they even acknowledging, much less addressing, the question of what consciousness actually is?

In picking out multiple materialist theories and principles, many overlap or nest, obviously, but by presenting them separately, I try to tease out emphasis and nuance. The list cannot be exhaustive.

Note that this Philosophical subcategory both presents theories that are central tenets of Materialism and houses methodological positions in the naturalistic orbit.

Footnote

[1]. In producing and hosting Closer To Truth over the years, I have interviewed David Chalmers and John Searle multiple times. One of my favorite Closer To Truth TV episodes is a retrospective of three interviews I did with Dave and John over a period of 15 years: 1999, when Dave and John were together on the same panel during the first season of Closer To Truth (roundtable format); 2007 (some months apart); and 2014, both at the 20th anniversary of the “Toward a Science of Consciousness” Conference in Tucson, Arizona (Chalmers & Searle, 2014).