Dualisms—Overview

Dualism is the theory of consciousness that requires two radically distinct parts: a physical brain, obviously, but also, in addition, a separate, nonphysical substance that is not only independent of the brain but also not of the physical world (as presently conceived). This would mean that reality consists of (at least) two ontological categories—physical and nonphysical, whether substances, properties, aspects, dimensions, or planes of existence. Dualism is often called “substance dualism” to distinguish it from “property dualism,” which is ontologically different. In general usage, “dualism” means substance dualism.

For dualism to be true, what follows must be that the physical world, at its most fundamental level of fields and forces, is not in some way causally closed, and that mental properties play a causal role in affecting the physical world. This perspective, often called interactionism, provides that physical states cause phenomenal states, and phenomenal states cause physical states, and whatever psychophysical laws there may be will operate in both directions (Chalmers, 2003).

Core Definition and Interactionism

Common forms of dualism identify the essence of the person with a nonphysical “soul,” generally an immortal soul. This kind of “soul-centered dualism” is also the theory of consciousness most widely believed by the vast majority of the world's population, largely implicitly via acculturation to belief systems, whether organized religion or folk traditions. Dualism (substance dualism), certainly, is the default doctrine in the Abrahamic religions of Judaism, Christianity, and Islam.

Dualism is largely rejected by philosophers, at least by most professional philosophers in the West^[1] (PhilPapers Survey, 2009, 2020). Dualism has fallen out of philosophical favor for at least four reasons. (i) No Interactions: Given the scientific understanding that the physical world is a causally closed system in that every event has a prior, physically efficient cause, how could anything outside such a closed system affect it? (Goff, 2020). (ii) Not Parsimonious: Two kinds of world stuff seem excessively complex; Occam's razor cuts unnecessary entities in explanations. (iii) No Knowledge: Souls are slippery; how to know anything about how they work? (iv) Fading Divine Creator: With God less prominent in academia, there seems to be one less way to create or allocate souls.

Critiques and Variations

In trying to characterize souls (assuming for a moment that souls do exist), we ask questions. Are all souls exactly the same, as all electrons in the electron quantum field are the same? Are souls undifferentiated (everyone gets the same “starter kit”), or specially tailored to each individual? Are souls created by God? Or are souls the inevitable, automatic product of a set of deep psychophysical laws? In other words, given specific, complex structures of atoms, do souls pop into existence? Or are souls always existing, part of a cosmic consciousness—journeying, reincarnating, transitioning, transforming, reincarnating …?

Notably, because consciousness, under dualism, would require both a non-physical substance and a physical brain (somehow working together), it is conceivable, following the death of the body and the dissolution of the brain, that this nonphysical substance by itself could maintain some kind of existence, conscious or otherwise. (Although this nonphysical substance is traditionally called a “soul”—a term laden with theological burdens—a soul is not the only kind of thing, or form, that such a nonphysical substance could be.)

Philosopher Dean Zimmerman reviews “a spectrum of dualisms” resulting from different meanings of “nonphysical.” Are souls simple, with no parts, or composite, with internal components (whether fixed or flexible)? To pose an extreme, could souls be abstract objects, outside of space and time, necessary existents? Most dualists would have souls as concrete, nonphysical objects. Some would even have souls extended in space, sharing the same special coordinate system as bodies (Zimmerman, 2005).

Philosophical Responses and Contemporary Views

David Bentley Hart welcomes confrontation by claiming that most early modern scientists were better able to understand the mind-body problem than are many in the sciences today. The 17th-century solution to the seeming irreconcilability of mind and matter was “to adopt a casual and contented dualism, allowing the mental and the physical each its own discrete autonomous sphere: nature, not being teleological or intentional in any way, is nothing like mind; mind, not being composite, purposeless, and impersonal, is nothing like nature.” The two can somehow interact, probably, Hart suggests, through the sheer power of God, but “neither is reducible or even qualitatively similar to the other.”

Hart recognizes the inherent problems in describing “any kind of coherent ontological, causal, or epistemological continuity between the two spheres”—Hart himself is a monist—“it [dualism] was nowhere near so magnificent a disaster as the later, materialistically monistic attempts to reduce mental events to mechanical [processes] have so far proved” (Hart, 2019a, 2021a).

To Galen Strawson, “Dualists who postulate two distinct substances while holding that they interact causally not only face the old and seemingly insuperable problem of how to give an honest account of this interaction. They also face the (even more difficult) problem of justifying the claim that there are two substances.” To think that dualism has anything in its favor, Strawson asserts, “is simply to reveal that one thinks one knows more about the nature of things than one does—and it has Occam's razor (that blunt, sharp instrument) against it” (Strawson, 2008). The dualism theories that follow in this section challenge this denial.

Jaron Lanier says, “You've got two choices. Either you know everything [about consciousness], or you organize your ignorance in some intelligent and organized manner. Dualism is the most honest manner of organizing your ignorance, okay?” (Lanier, 2007b).

As noted, Closer To Truth viewers regularly send me diverse theories related to consciousness, some just ideas, some elaborate systems, and occasionally they are hard to classify. For example, a consciousness system operating independently of the central nervous system, constituted by “a Material B” (exhibiting “coupling properties” beyond the boundaries of physics) and explored by “memory-related thought processes” and “illogical nonlinear-thinking”^[2] (Ma et al., 2023).

It is well known that mental causation is a vexing problem for dualists. By what conceivable mechanism could nonphysical stuff affect physical stuff? This is not a primary issue for this Landscape, but it is for Dualism.

Again, the purpose of this section on Dualisms as a theory of consciousness is to describe various kinds of dualism, not to argue in favor or against (a self-imposed hurdle on which I occasionally trip).

Footnotes

[1]. The first PhilPapers Survey of philosophy faculty and PhDs, conducted in 2009, reported: Accept or lean toward: Physicalism, 56.5%; Non-physicalism, 25.9%; Other, 16.4%. (Bourget & Chalmers, 2009; PhilPapers Survey, 2009). The latest Survey in 2020 showed a modest but meaningful shift away from Physicalism (51.93%) and toward Non-physicalism (32.08%); Other, about the same (16.56%) (Bourget & Chalmers, 2023; PhilPapers Survey, 2020).

[2]. The three Chinese scientists are, inclusively, from Mainland China, Taiwan, and the USA. It is good that consciousness can catalyze harmony.