Chalmers and McQueen’s Quantum Collapse

Philosophers David Chalmers and Kelvin McQueen readdress the question of whether consciousness collapses the quantum wave function. Noting that this idea was taken seriously by John von Neumann and Eugene Wigner but is now widely dismissed, they develop the idea by combining a mathematical theory of consciousness (Integrated Information Theory) with an account of quantum collapse dynamics (continuous spontaneous localization). In principle, versions of the theory can be tested by experiments with quantum computers. The upshot is not that consciousness-collapse interpretations are clearly correct, but that there is a research program here worth exploring (Chalmers & McQueen, 2022).

Chalmers and McQueen draw parallels between our understanding of quantum mechanics and consciousness. On the one hand, “One of the hardest philosophical problems arising from contemporary science is the problem of quantum reality. What is going on in the physical reality underlying the predictions of quantum mechanics?” On the other hand, “Another of the hardest philosophical problems arising from contemporary science is the mind-body problem. What is the relation between mind and body, or more specifically, between consciousness and physical processes?”

Collapse Models and Dualism

The authors argue that, “where consciousness is concerned, there are reasons to take dualism seriously”—notwithstanding the fact that dualism is dismissed by a large majority of philosophers. One common reason, according to Chalmers, “is that physical theories explain only structure and dynamics (the so-called ‘easy problems’ of behavior and the like), and explaining consciousness (the so-called ‘hard problem’) requires explaining more than structure and dynamics” (Chalmers, 2003; Chalmers & McQueen, 2022). These reasons need not lead to substance dualism, they say, “on which consciousness involves a separate nonphysical entity akin to an ego or soul, but they have led many theorists to adopt a form of property dualism where consciousness is accepted as a fundamental property akin to spacetime, mass, and charge.”

As Chalmers and McQueen observe, “the most common reason among philosophers for rejecting property dualist theories of consciousness is an argument from physics. This argument runs roughly as follows: (1) every physical effect has only physical causes, (2) consciousness causes physical effects, so (3) consciousness is physical. The key first premise is a causal closure thesis, supported by the observation that there are no causal gaps in standard physics that a nonphysical consciousness might fill.”

Here, the authors posit, not without controversy and opposition, that “wave function collapse in quantum mechanics appears to be precisely such a gap, and consciousness-collapse models are at least not obviously ruled out by known physics.” They note the irony: “The situation is that many physicists rule out consciousness-collapse models for philosophical reasons (they are dualistic), while philosophers rule out property dualist models for physics-based reasons (they violate causal closure).”

The upshot, Chalmers and McQueen claim, is that “a central reason to reject the consciousness-collapse thesis (it leads to dualism) and a central reason to reject interactionist property dualism (it violates the causal closure of physics) provide no reason to reject the two views when taken together.”

Chalmers and McQueen offer a disclaimer, lest their claims seem too grand. “We are not trying to solve the hard problem of how physical processes give rise to consciousness. We are giving an account of the causal role of consciousness that can be combined with many different approaches to the hard problem. Our approach is consistent with both materialist views, on which consciousness is identified with a complex physical property, and dualist views, on which consciousness is a primitive property that correlates with physical properties.”

Compatibility with Materialism

The authors stress that “the consciousness-collapse thesis need not lead to dualism. It is compatible with materialist views on which consciousness is a complex physical property. For example, let us suppose a materialist version of integrated information theory on which consciousness is identical to ɸ, the property of having integrated information above a certain threshold. Then the consciousness collapse theory will say that the version of integrated information theory on which consciousness is identical to ɸ causes collapse. This interpretation of quantum mechanics will involve a fundamental physical law saying that under the conditions specified by ɸ, collapse is brought about according to the Born rule. A fundamental law involving a complex physical property may be unlike familiar physical laws, but it involves nothing nonphysical” (Chalmers & McQueen, 2022).