Cartesian dualism has been a point of contention in philosophy since at least, well, Descartes. The dispute is whether the mind is a separate, immaterial entity from the physical body. Problems have plagued the dualist view since the time of Descartes, primarily how it is that the immaterial mind and material body interact.
Now days when people think of the soul they think of it as a separate, immaterial entity inhabiting the physical body. This wasn’t always the case. Philosophers like Aristotle and Thomas Aquinas viewed the soul as a formal cause of the person. It was that thing which we would identify as the animating aspect of an organism, but it wasn’t necessarily some ghostly entity inhabiting a body, but a part of the body itself. Even plants and animals had souls, though of a lesser kind. Plants had a nutritive soul, wherein they sought out nutrients; animals had a nutritive and sensitive soul, having the faculties of sensation added; humans had a nutritive, sensitive, and rational soul, wherein they had the extra faculties of reason.
Descartes wasn’t the originator of the separate, immaterial soul, but his philosophy of methodological doubt and its conclusion of cogito ergo sum made it a hot philosophical issue in the west. Opposed to this view are materialists, who think that all that exists is physical, material substance – that the mind is just the coordinated firing of neurons. Just as Cartesian dualism has its issues with the interaction of immaterial and material substance, the materialist view has the problem of explaining such phenomena as qualia and the hard problem of consciousness. Of course, dualism doesn’t necessarily answer these questions, merely pushing it back a level, but materialism has yet to explain it either, generating a sort of infinite regress of homunculi.
Materialism also has the problem of explaining how there can be multiple instantiations of a mind. Minds can emerge from differently patterned neural configurations, which means it’s not purely the precise configuration of the physical substrate of the brain that determines the existence of the mind. This is true between different people, but also within the same person – a person F at time t1 has a different brain pattern than the ‘same’ person F at time t2 due to neural plasticity, yet they will identify themselves as the same person (multiple instantiations in a single person).
A sort of middle ground, proposed by Douglas Hofstadter in his 1979 opus “Gödel, Escher, Bach” is the idea of downward causation. Using ideas of self-reference, such as a code that contains the instructions for changing itself, Hofstadter thinks that the mind is the brain’s ability to change itself.
The mind is a sort of epiphenomenon that emerges from the complexity of the brain which is able to sort of ‘reach down’ back to its constituent substrate to alter it. The neurons in the brain, upon thinking, are a closed system. Yes, there is input from senses, but if it were just sense-stimulation to behavior, there would be no need of consciousness. The epiphenomenal mind can reach into its own memories to pull forth Ideas for its own internal consideration.
In this middle ground conception, the mind is still dependent on a physical substratum, the way something simpler like ‘shape’ requires there to be a physical existence which is the shape. The shape itself an emergent property of the configuration of atoms and molecules from which the object is composed. The mind is just a much more sophisticated emergent property than mere shape, being an emergent property of a complex dynamic system like the brain. Since the mind can’t be extracted or measured, it is an immaterial entity.
If this recursive conception of the mind-body problem is true, what implications might it have for artificial general intelligence (AGI)? I think it could give us more confidence that an AGI is conscious. It obviously would do away with the problems of dualism, where one would have to wonder how a material and non-material entity come together – in other words, would a machine be instilled or imbued with a soul once it reached some sufficient criteria of intelligence? I think the emergent property conception of the mind is also a possible solution to the hard problem of consciousness that arises from strict materialism – dynamic complexity of particular kind is sufficient for the emergence of consciousness.