Descartes’ theory of dualism that the mind and body are independent of each other, yet can interact together, is ultimately unconvincing as a result of three main limitations. While his explanation for how the mind and the body communicate is excessively vague and impractical, it also violates the law of the conservation of energy and neglects a scenario where if the brain is damaged, our mental powers could be compromised, despite the mind and brain’s being separate to each other. This essay, in essence, will explain the logic behind Cartesian dualism before discussing how all these three criticisms render it false.
Descartes argues that the world is made up of two distinct classes; those which are extended in space and those which have no extension in space. Whereas the body, including the brain, would qualify as the former, the mind would be classified as a thinking substance which cannot be extended in space. The body is material, observable and unconscious while the mind is non-observable, non-spatial and conscious. Furthermore, there is interaction between both the mind and body, as each one can exert influence over the other. According to Descartes, this is possible due to the pineal gland in the brain, the locus for mind-body interaction. There is evidence for both the mind and body’s being separate entities. Mental and physical realms do, after all, have very distinct properties. Mental events involve subjective qualities; sensations which cannot be considered physical. There exists no area in the brain which can be true or false yet our thoughts can be just that. It would be impossible to decipher what we were thinking by simply looking at brain waves and, as such, Descartes’ theory that the mind is detached from the body, at first, seems plausible. Additionally, his view of mental causation does accord nicely with common sense. We are surrounded every day by scenarios which alternate between physical and mental events continuously. As an example, were I to play some music (physical event), I may feel pleasure (mental state), prompting me to sing loudly (physical event), potentially irritating my friends in the same room (mental event). Such a sequence could continue further but the obvious relationships between physical events and mental events that occur within our lives serve to justify Descartes’ view that mind and matter are two individual substances, able to exert causal effects on one another.
Despite this position of mental causation appealing to our common senses however, Descartes’ view is overly simple and is extremely difficult to validate based upon any empirical evidence. While he does not suffer when explaining body-body causation as it is clear bodies can cause change to each other through impact, Descartes does have an issue in explaining mind-body causation. If the mind is separate from the brain, we have no clear way of understanding how they are able to interact with one another due to a gap in between them. There exists no physical property such as force which can justify interaction between the mind and body, like there is with interaction between two bodies. Cartesian dualism suffers in this respect, as it requires an explanation for how something without any physical properties has physical effects. If the mind cannot exist in the physical realm, it is unclear how it could possibly communicate with the brain, a material object. A sensation that I feel in my mind, for example the pleasure from playing music as described earlier, is not spatially locatable. This pleasure is not observable so where the interaction between the mind and the body takes place lacks clarity. Ducasse (1961, 88; cf. Dicker pp. 217-224) Gilbert Ryle
Even if it were said that the feeling of pleasure from listening to music were taking place within the brain, this would also be incoherent due to the fact that it is my ear rather than my brain which notices the sound. In defence of Descartes, the fact we do not completely understand mind-body interaction does not necessarily mean it is impossible. Although Cartesian dualism cannot explain exactly how minds and bodies interact, this does not discredit the theory completely, rather just proves that dualists do not know everything about metaphysics. Even so, the absence of an explanation for mind-body causation results in Cartesian dualism becoming a much less persuasive argument. Despite not discrediting it completely and with empirical evidence, the interaction problem does highlight Descartes’ theory as overly simple and vague, itself lacking the evidence required to be convincing.
In contrast, Cartesian dualism is actually scientifically unacceptable as it violates the principle of the conservation of energy. We live in a world which is a causally closed system and, consequently, every event in the material world is caused by another material event. As a result, although energy and mass may be converted, the total amount of both must remain constant. Therefore, this hinders Descartes’ theory for any interaction concerning an immaterial mind and a physical object as it would involve an increase in energy, despite the scientific affirmation that it can neither be created or destroyed. Such an increase would be necessary since it takes physical energy to do physical work. For a mind to have an impression on the physical universe, it would either have to introduce energy from its own non-material realm or use some from the physical realm for itself. Yet, as energy is strictly only transferrable, the mind would never have any to utilise. (Lycan, 1996, 168) Heil, Philosophy of Mind, p. 26
Potentially, it could be the case that the mind does effect change on the universe, contributing energy to the physical world but by such a negligible quantity that this could not be detected. However, such an argument is close to denying completely the principle of the conservation of energy, a principle already too well-established to truly be doubted. Instead, from a dualist’s perspective, it would be more appropriate to argue that the law of the conservation of energy solely applies to material interaction and is not relevant to how mind might interact with matter. In a similar case, if God were to exist, would we question his ability to create miracles simply as they violate certain physical laws such as thermodynamics? Keith Campbell 1970 p 54
However, like with a dualist’s response to the interaction problem, this relies on an assumption which cannot be proven yet is critical to the theory of Cartesian dualism’s being plausible. Thus, Descartes’ theory has another limitation which drastically reduces its validity and, unlike the interaction problem, this critique of dualism is close to empirical evidence against it.
Another weakness of Cartesian dualism is that, if a brain became damaged, the mental properties of a person would change or be compromised. However, if the mind is distinct from the body and brain, as explained by Descartes, how can the mind be injured as well as the brain? It does not seem possible, if both the mind and body are ontologically independent, that a physical injury to the brain could result in sizable effects on mental states such as memory. It could be claimed by a dualist that such a case would just be the result of the brain failing to communicate properly with the mind. Perhaps the brain is just an information router which is no longer be able to send inputs from the body to the mind and receive transmissions from the mind to send to the body as successfully. This example would preserve the idea that the mind is not actually damaged but the brain, defending Cartesian dualism. However, for it to simply be a ‘communication problem’ seems insufficient. The connections between brain damage and the mental effects which follow it lead to a much more conclusive explanation than there being just a communication problem, for which the method of communication a dualist has no ability to prove. As such, the argument from brain damage also contributes to Descartes’ theory’s being false.
To conclude, Cartesian dualism suffers from being unable to explain how and where the mind and body interact. However, while this weakens the argument considerably, dualism’s failure to respond to the argument from brain damage as well as the argument from physics means it can be considered incorrect. It ignores the fact that it violates the law of the conservation of energy and offers no sufficient explanation for how mental states can also change in the case of brain damage. As a result, the theory becomes scientifically unacceptable and has no explanation for certain, not uncommon, scenarios. For this reason, Cartesian Dualism is false.