Part 1 - What is Cartesian dualism?
In Naming and Necessity, Kripke evokes Cartesian dualism by stating: "a person or mind is distinct from his body since the mind could exist without the body." This argument rests on the plausibility of the existence of a compelling story, that takes us from imagined to the logical possibility of a disembodied mind. Once this is established, necessary identity makes the argument for the distinction valid1. In the following text, I'll show how Descartes2 resorts to the real possibility of a disembodied mind while building up to the argument about the nature and substance of mind and body. I'll end with considerations about the plausibility of the disembodied argument.
In Meditations II, devoided of all knowledge that could be doubted3, Descartes starts his first-person construction of a true set of premises, evading the illusions of the evil demon and reasoning only by the 'Natural Light'. He entertains the possibility that he might not have eyes with which to see or even a body at all, that everything body related might be a dream and that the senses could be telling a story that doesn't match reality at all. These possibilities strip him of every certainty other than he exists and that he's a thinking thing. This, he states, is what can be truly known about the nature of mind.
External objects, illusory as they may be, constitute further evidence that he exists. In meditation VI he establishes the nature of the body as a separate substance and further clarifies how God would aid him in the construction of a disembodied mind. Referring to faculties like imagination and contrasting it with the innate understanding of the mind, he states: "I can clearly and distinctly understand myself as a whole without these faculties; but I cannot, conversely, understand these faculties without me." Given this and his God-given propensity to believe in external corporeal things, he conjectures as to the best explanation, that the body truly exists. Still holding that he can't claim any certainty through the senses about these external objects, he can however reach certainties when they are perceived as mathematical concepts. Further evidence for the dualism of mind and body is that the mind is a whole and not divisible, while the same doesn't hold for the body - matter is capable of being separated. Once he establishes substance dualism, he addresses the conceivability objection by evoking God - just because we can not come up with a coherent narrative about how to separate mind and body, given that these things are different and that things which are not the same can be separated by God, at the very least He would be capable of settling the issue.
Accepting the possibility of disembodiment is controversial. It's hard to picture how mental states would leave physiological states unaccounted for, so much so that Descartes ends up placating these considerations by having to evoke God. Even if we accept this strategy, however, once body and mind are established as different substances, this raises the interaction problem - how can we establish causal relations between one and the other?
Part - 2 Can one reasonably be a dualist in this day and age?
Carl Sagan once referred to science as a candle in the dark, the only tool we have to dimly illuminate our way out of ignorance. The body of knowledge about the brain we have acquired in recent years fuels our hopes of cracking the age-old question about the nature of the mind. Still, at every step of the way, philosophers have to grapple with a set of intuitions that keep popping up: how does something that feels so distinctly private and immaterial, be reconciled with this very concrete set of facts we're learning about the brain?
This work will go through several takes on the mind-body problem. How some tried to reframe it as a category error, how some physicalist descriptions leave out our strong intuitions about the mind, claims about the identity of mind and brain and how we could rescue dualism from these claims. Finally, we'll look at whether or not science can make claims about the mind-body identity or if it is left completely unable to address it. To answer the question "Can one reasonably be a dualist in this day and age?", we will not look at an exhaustive description of the different types of dualism. Instead, we'll focus on the ongoing conversation between a scientific rationale that looks for objective descriptions, and the personal intuitions about the qualitative nature of thoughts, sensations and others, that challenge being captured this way.
Descartes captured the intuitions about the distinct nature of body and mind in Meditations VI as follows: "I have a clear and distinct idea of myself, in so far as I am simply a thinking, non-extended thing; and on the other hand I have a distinct idea of body, in so far as this is simply an extended, non-thinking thing". This duality between mind and body still has a tight grip on philosophical discussions about the nature of mind, to this day.
Framing body and mind as separate entities, leaves us with a few hurdles to clear - how are these things supposed to interact with one another, and is one reducible to the other? This is otherwise known as the mind-body problem which, stated in another way - how can you have a causal account of how mental and physical events interact with each other, if there doesn't seem to be an overlap regarding their properties?
One option is to reframe the issue. In Descartes Myth (Ryle, 1949), the author dismisses Cartesian dualism as the "Dogma of the Ghost in the Machine" and that the split was actually a category mistake. Ryle doesn't try to deny the mental, just that saying: "there occur mental processes does not mean the same thing as there occur physical processes." Therefore, he concludes, reducing one to the other would make no sense. According to Ryle, Descartes being a man of faith had a reactionary take against the zeitgeist of the day, namely, Galileo's mechanistic account of the physical world.
A modern view of physics points us in the direction of there being a complete story of the brain based on neural events, that goes from sensory input to behaviour. This explanatory narrative, which derives from the causal closure of physics, leaves outside the picture our strong intuitions about how thoughts, wills and wants drive our behaviour. Some state that this sort of folk psychology explanation erroneously attributes volition to entities that otherwise have none. Churchland in "Eliminative Materialism and the Propositional Attitudes", (Churchland, 1981), even draws the following comparison: "In primitive cultures, the behaviour of most of the elements of nature were understood in intentional terms." The Eliminativist take is to downright deny that mental contents can have really no causal power.
Under this brand of physicalism, the absence of the subjective mind - qualia and the content of thoughts - sticks out like a sore thumb. Epiphenomenalism addresses half the problem, establishing one way causation - stating that the mental emerges from neural activity but that it has no causal power over the physical. Jackson in "Epiphenomenal Qualia" (Jackson, 1982) illustrates this point with the story of Mary, who after having lived in a black and white room all her life studying colours exhaustively, is left wondering what sort of magic a colour TV is, when she first sees one. The story illustrates what proponents of qualia swear by: once you describe all the facts about a mental phenomenon, there still is a residue that can not be captured with descriptive knowledge. If you accept that there was indeed something that Mary didn't know, you opened the door to the "Ghost in the Machine."
One way to deny dualism is to accept the type-identity theory, which is another physicalist take on the mind-body problem. Kripke in Naming and Necessity, (Kripke, 1972) rescues Descartes' intuitions from a modern scientific audience, which should have had no issue with identifying mental events with brain events. His argument rests on there being a possibility of these two things being distinct, and can be summed up as follows: given that you can imagine a disembodied mind, this should serve as a guide for conceivability and therefore (if you accept that) the logical possibility of them being distinct. Given this logical possibility, you could have a world where there was a given mind without its (actual world) body. According to Kripke, given that the identity between these two things is a case of necessary identity, the logical possibility of a disembodied mind makes the relation between the two only a case of contingent identity.
This road from imagined possibility, to conceivability and possibility, opens up an attack vector on Cartesian dualism. Descartes himself ends up having to resort to God to settle this point, stating that if these two things can be conceived as being distinct, then it doesn't matter how difficult it is to imagine how they could be split and exist separately. Given that they are distinct, then at the very least, God would be able to split them. Understandably, however, this doesn't sit too well with a modern scientific and contemporary take on the subject.
Christopher Hill in "Imaginability, Conceivability, Possibility and the Mind-Body Problem", (Hill, 1997) addresses precisely the issue with going from imagined possibility to an actual logical possibility, resorting to Thomas Nagel's views on sympathetic and perceptual imagination. He argues that because we imagine brain states using perceptual imagination and mental states using sympathetic imagination, we can apparently see no contradiction in imagining one without the other. Because of this, Hill argues, imaginability shouldn't serve as a guide for logic possibility in this instance.
Maxwell in "Rigid Designators and Mind-Brain Identity" (Maxwell, 1978) has another take on Kripke that tries to conserve type-identity theory. Starting off from agreeing with Kripke on the necessary identity of pain and mental events, he states that there is an "illusion of contingency" between the two that explains why a mental event and the correlated brain event would not appear necessarily identical. Quoting Maxwell: "After God created b76 [a given brain event], ... [that] was the creation of pain39 [the mental event respectively correlated] for 'they' are the same event. What was a substantive task for the Deity was to give pain39 (alias b76) the kind of (contingent) neurophysiological causal role that it has." After addressing Kripke's criticism he follows up by saying that this is not even the main issue with type-identity theory. In his view, the main issue would be: how can properties of mental events differ significantly from properties of physical events? The phenomenal experience of a continuous patch of red can find no physical equivalent in the brain that is both red and continuous. He argues that although neurophysiology offers the best explanations of the neural causal networks, we're pretty much in the dark regarding the "intrinsic" properties of individual brain events and, "Thus the possibility is entirely open that some of the brain events just are our twinges of pain, our feelings of joy and sorrow…", offering that eventually, science will be best suited to close this gap.
Other authors suggest otherwise, stating that science will forever be in the dark, that even if we uncover the whole story about the causal structures of brain events, that will always leave intrinsic aspects unaccounted for. Chalmers in the Conscious Mind, (Chalmers, 1996) proposes that the logical conceivability of philosophical zombies provides us with a guide for the possibility of this type of scenario. While consciousness supervenes on the brain, due to the causal closure of physics, all we will always have is an extensive description of neurophysiology. Qualia and the causal power of mental events will remain unaccounted for.
Perhaps the version of dualism proposed by Descartes, with the mind being "a thinking thing" and the body this separate "extended" thing, won't find much expression in today's scientific circles. However, as we have seen, given the elusive nature of consciousness that defies being probed by the best scientific theories, a case can be made that there will always be an aspect of the mind that remains ineffable, impossible to be captured as mere descriptive knowledge. Therefore, the apparent substance distinction can always find a way to be reframed.
1 Mind and body would be necessarily identical if they were identical in every possible world. A real possibility of them being distinct means that there is at least a possible world where that is not the case, voiding necessary identity and making the distinction argument valid.
2 Based on Meditations on First Philosophy II and VI.
3 Referring the method of systematic doubt here.
- Robinson, Howard, "Dualism", The Stanford Encyclopedia of Philosophy (Fall 2020 Edition), Edward N. Zalta (ed.), URL = plato.standford.edu - dualism.
- Robb, David and John Heil, "Mental Causation", The Stanford Encyclopedia of Philosophy (Spring 2021 Edition), Edward N. Zalta (ed.), URL = plato.standford.edu - mental causation.
- Chalmers, D.J., 2002, Philosophy of Mind: Classical and Contemporary Readings.
- Chalmers, D.J., 1996, The Conscious Mind.