Dual-Aspect Monism

An illustration of dual-aspect monism in which the two shadows symbolize consciousness and physics. Note that it is not logically possible to alter or remove a shadow directly since its state is determined by the cylinder.

Dual-Aspect Monism as defined in this wiki is the claim that physics and consciousness are two aspects of the same underlying phenomenon. As such, their relationship is like that between the edges and faces of a cube, or between two shadows cast by a cylinder from different angles. Crucially, this relationship is a logical consequence of the structure of the universe, rather than a fact governed by an explicit set of laws.

Causality and Science

The coupling between conscious and physical states implies that any conscious property, state, or causal event has a physical analog. In other words, it makes consciousness a valid target of scientific study. As an example, the conscious event "I felt an itch and decided to scratch it" may have the physical analog "nerve fibers in my body sent signals to my brain, which issued motor commands to my hand to scratch the itch". The fact that the relationship between consciousness and physics is fixed means that finding such analogs constitutes progress toward a complete theory.

The flip side is that incorrect theories may be rejected due to violating this coupling. An example is the causal discontinuity that results from the binding criterion of Integrated Information Theory. That said, most proposals are not formalized enough to construct similar arguments.

Completeness

A crack on the right side of the cylinder doesn't affect either shadow, implying that both shadows are incomplete "aspects" of the cylinder. That said, note that this example is only included to help explain the concept of completeness; the illustration does not make a claim about completeness of consciousness or physics in our universe.

If one accepts dual-aspect monism, it begs the further question whether the two aspects are complete, i.e., describe the underlying system fully. Mathematically speaking, this question determines the type of mapping between both aspects. There are several possibilities, e.g.:

• If both aspects are complete (one-to-one mapping), any change to the physical aspect causes a change to the consciousness aspect and vice-versa.
• If only the physical aspect is complete (many-to-one mapping from physics to consciousness), several physical states may correspond to the same conscious state, but different conscious states always correspond to different physical states.

Any functionalist would likely privilege the second option since several physical systems can implement the same algorithm. Conversely, the first option may be considered the most elegant (see also the section on metaphysics), though it implies a degree of panpsychism since the conscious aspect can only be complete if all physical structures are at least minimally conscious. Note that if both aspects are complete, compatibility with dual-aspect monism becomes a necessary and sufficient criterion for a theory of consciousness to be correct.

Other possibilities (like only the conscious aspect being complete, neither aspect being complete, or completeness varying across contexts) are conceivable but rarely discussed.

Relationship of Dual-Aspect Monism to Other Views

For the following discussion, note that dual-aspect monism is defined entirely as a claim about causality (plus Consciousness Realism, i.e., the claim that frame-invariant consciousness exists). Other definitions of dual-aspect monism will rarely disagree with the one given here but might include additional metaphysical claims. In those cases, the findings from the following discussion may no longer hold. Importantly, note that the causal claim is sufficient to identify consciousness as a valid target of scientific research.

The views discussed here can be considered approaches to the Mind-Body Problem. More precisely, they are different approaches to explaining how consciousness can fit into a universe that appears to obey a set of laws that don't explicitly mention consciousness.

Illusionism/Eliminativism

Dual-aspect monism implies consciousness realism and is thus incompatible with theories disputing realism.

Epiphenomenalism

Dual-aspect monism claims that the relationship between physics and consciousness is logically entailed by the underlying phenomenon, which epiphenomenalism explicitly disputes. Under epiphenomenalism, a complete description of the universe requires laws about how consciousness arises from physics, which are laws above and beyond the laws of physics themselves. In his book The Conscious Mind, David Chalmers has called these Psychophysical Laws (p. 127, emphasis added):

Where we have new fundamental properties, we also have new fundamental laws. Here the fundamental laws will be psychophysical laws, specifying how phenomenal (or protophenomenal) properties depend on physical properties. These laws will not interfere with physical laws; physical laws already form a closed system. Instead, they will be supervenience laws, telling us how experience arises from physical processes. We have seen that the dependence of experience on the physical cannot be derived from physical laws, so any final theory must include laws of this variety.

In particular, the philosophical zombie (a person that exhibits no consciousness despite being physically identical to a human) is a coherent thought experiment under epiphenomenalism but a logical impossibility under dual-aspect monism.

Interactionism

Wikipedia defines interactionism as "the theory [...] that matter and mind are two distinct and independent substances that exert causal effects on one another". Dual-aspect monism claims that consciousness and physics are part of the same substance, and thus, it is generally considered incompatible with theories that identify them as different substances. That said, identifying consciousness as a separate substance doesn't explain how causality works for that substance. If the substance is itself lawful, one is again confronted with the problem of placing consciousness within a system that can be explained without invoking consciousness. In other words, one must still solve the mind-body problem, just restricted to a smaller domain.

Note that David Chalmers made the same point in his book (p. 158):

Some might object that psychons (or ectoplasm, or whatever) are entirely constituted by their phenomenal properties. Even so, there is a sense in which their phenomenal properties are irrelevant to the explanation of behavior; it is only their relational properties that matter in the story about causal dynamics. If one objects that still, they have further intrinsic properties that are causally relevant, we have a situation like the one that arose above with phenomenal properties intrinsic to physical entities. Either way, we have a sort of causal relevance but explanatory irrelevance. Indeed, nothing especially is gained by moving away from the causal closure of the physical. We still have a broader causal network that is closed, and it remains the case that the phenomenal nature of entities in the network is explanatorily superfluous.

Thus, although this framing is nonstandard, interactionism is more appropriately defined as the claim that consciousness operates outside the current laws of physics, with the causal behavior of that substance left unspecified. In other words, one is forced to choose between a dual-aspect vs. epiphenomenalist view for consciousness either way, which makes interactionism technically compatible with dual-aspect monism. That said, note that QRI explicitly holds that consciousness operates within the laws of physics and thus disagrees with interactionism regardless.

Panpsychism

As defined by the Stanford Encyclopedia of Philosophy, panpsychism is "the view that mentality is fundamental and ubiquitous in the natural world", which is compatible with the causal claim of dual-aspect monism. Note that it's possible for consciousness to technically exist everywhere but usually not being bound together, which would imply that most of the universe consists of many disconnected bits of qualia (sometimes called "mind dust"). In this case, one can start from a panpsychist ontology but recover a universe in which globally bound pockets of qualia – i.e., unified conscious systems – are rare.

Idealism

Wikipedia defines idealism as the claim that "[...] most fundamentally, reality is equivalent to mind, spirit, or consciousness" (which is similar to the definition by the Stanford Encyclopedia). As such, idealism is also compatible with dual-aspect monism (see the section on metaphysics for an elaboration on this point).

That said, "idealism" is also an overloaded term that can vary along two axes. The full specification for the concept referred to in the paragraph above would be ontological objective idealism, where

• ontological idealism is distinct from epistemological idealism, which is a claim about knowledge that's independent of consciousness; and
• objective idealism is distinct from subjective idealism, which is the claim that the universe is fundamentally consciousness, plus the additional postulate that external objects don't exist independently of minds. (QRI rejects this additional claim.)

Property Dualism

Wikipedia defines property dualism as follows:

Property dualism describes a category of positions in the philosophy of mind which hold that, although the world is composed of just one kind of substance—the physical kind—there exist two distinct kinds of properties: physical properties and mental properties. In other words, it is the view that at least some non-physical, mental properties (such as thoughts, imagination and memories) exist in, or naturally supervene upon, certain physical substances (namely brains).

While this definition is compatible with dual-aspect monism, other definitions sometimes emphasize the logical irreducibility of mental properties, in which case the principles become incompatible. In this case, logical irreducibility means that the mental properties (i.e., the "consciousness aspect") do not logically have to accompany the physical aspect, or in other words, that it would have been possible to have the same physical properties with different mental properties. This distinction is crucial both for the theory's implications for science, as well as for its complexity, and thus, its plausibility given Occam's Razor.

E.g., the Stanford Encyclopedia writes:

[...] The irreducible language is not just another way of describing what there is, it requires that there be something more there than was allowed for in the initial ontology. Until the early part of the twentieth century, it was common to think that biological phenomena (‘life’) required property dualism (an irreducible ‘vital force’), but nowadays the special physical sciences other than psychology are generally thought to involve only predicate dualism. In the case of mind, property dualism is defended by those who argue that the qualitative nature of consciousness is not merely another way of categorizing states of the brain or of behaviour, but a genuinely emergent phenomenon.

Thus, property dualism may be compatible with dual-aspect monism but becomes incompatible if logical irreducibility is included in its definition. As always, it ultimately depends on one's interpretation of the concept.

Physicalism

QRI defines physicalism as the claim that the laws of physics fully describe the causal behavior of the universe. However, the term is more commonly defined as the claim that "everything is physical". This definition is too vague to make a definitive claim about its compatibility with dual-aspect monism, although compatible interpretations are certainly more common than incompatible ones. Some uses of the term primarily indicate a rejection of functionalism, which QRI agrees with.

The Core Idea and its Ontology

As illustrated in the preceding sections, the philosophical terminology around consciousness is not a clean decomposition of the hypothesis space, but a historically path-dependent swamp of concepts that frequently overlap, tackle separate aspects of the problem, and often have substantial ambiguity. Conversely, the position described in this article comes down to a simple idea: if one assumes that

• frame-invariant consciousness exists (i.e., one rejects Illusionism); and
• consciousness is causally active (i.e., one rejects epiphenomenalism); and
• consciousness is lawful (i.e., one rejects Libertarian Free Will along with any other proposal that postulates an inherently unlawful universe),

then it must be possible to (1) experience consciousness, and (2) describe it externally, where the relationship between both is not arbitrary but inherent from the nature of consciousness. This combination of (1) and (2) is enough to capture the core of the concept, and the different but compatible philosophical labels discussed in the previous section can be viewed as different expressions of the idea.

An alternative formulation that avoids philosophical labels altogether is given in the book The Mind Illuminated by John Yates et al. (p. xv):

[...] There is only one kind of “stuff,” and both mind and matter are mere appearances. When looked at from the outside, this “stuff” appears as matter, and as such has been the object of scientific investigation. But when examined from the inside, this exact same “stuff” appears as mind. Non-duality, as realized through direct experience in meditation, completely resolves this dilemma. [...]

Out of all available concepts that are compatible with this idea, dual-aspect monism makes the fewest metaphysical assumptions, and because of this, it is the label of choice throughout this wiki. However, if any external description of consciousness appears non-mental purely by virtue of being an external description, then it is arguably unnecessary to explicitly postulate two separate aspects. Instead, the existence of two aspects follows automatically from the fact that consciousness can be described from the inside and outside. Thus, if one wants to answer the ontological question in addition to the causal question, idealism may be the most philosophically satisfying view. If so, it may also be considered an argument for both aspects being complete.