George Moe — Fall 2020
This is an essay I wrote about Descartes' mind-body dualism for my philosophy tutorial.
As you peruse these lines, you might become aware of the experience of your reading: you seem to control your gaze as you scan the page and perceive characters forming comprehensible thoughts, and you seem to be able to mull and consider these thoughts more deeply at command. On top of it all, you feel this from a first-person perspective that is uniquely yours. This experience is what we may identify as the mind.
But what about animals? Do our pets feel the same awareness when they greet and play with us? Do insects feel “intent” as they scurry about their day? Could even simpler lifeforms, from worms to bacteria, have subjective experience?
Through his anatomical explorations, Descartes theorized that humans were the union of a mechanical “organic body” and a non-physical, soul-like “mind.” Could animals fit into one of these categories: mind, body, or mind-body union?
Although Descartes’ framework will serve as a starting point for our inquiry, I will argue that animals are not satisfactorily explained by any of these categories. I will motivate a better explanation: that they have minds which exist as a physical process of the body. This model will simply and directly explain behaviors which confound the Cartesian categories. So, I will press that we accept it as the best explanation.
The remainder of this paper is divided into five sections. In Section 1, I will detail Descartes’ concepts of mind, body, and mind-body union. In Section 2, I will show why animals are not satisfactorily explained by any one of these. In Section 3, I will motivate my alternative solution: mind as a process of the body. In Section 4, I will evaluate this solution against the evidence and consider an objection. Finally, in Section 5, I will close with a brief discussion of interesting upshots.
Descartes believes that humans are composed of two distinct things: the mind and the organic body (which I will refer to as just “body”). Based on anatomical studies, he concludes that the body is a purely physical, mechanical thing, while the mind is some non-physical, soul-like thing. He believes that humans are unique among all life as a union of the two, where the mind is intimately intertwined with the body.
To Descartes, the body is a supremely intricate machine—but just that, a machine. He writes: “I suppose the body to be nothing but a statue or machine...We see clocks, artificial fountains, mills, and other such machines which, although only man-made, have the power to move of their own accord in many different ways” (ap. 100 p. 99). Descartes is unimpressed by the body’s autonomy. Even man-made objects can move in response to input: wind-up toys can scurry around and even spring surprises at the push of a button. The body is easily as soulless as these clockworks.
In fact, Descartes is very open-minded about the capabilities of a soulless body because it is a sublime machine designed by God. He continues: “But I am supposing this machine to be made by the hands of God, and so I think you may reasonably think it capable of a greater variety of movements than I could possibly imagine in it, and of exhibiting more artistry than I could possibly ascribe to it” (ap. 100 p. 99). When we think of a machine, we imagine a limited device. It would be challenging for us to design a robot that could brush its teeth, pull back from a dangerous flame, catch a ball, cook a meal, and all the rest. But with God as the engineer, of course the body is fully capable of all these wonderful movements with which we are so familiar.
Yet, there is something the body lacks just as a machine lacks without its driver: a motivating soul. Descartes compares the body to a mechanical fountain, where its essential functions like breathing are as automatic as “the movements of a clock or mill, which the normal flow of water can render continuous” (ap. 141 p. 101). However, to change or direct these functions in a non-automatic way requires an extra force, “like the fountain-keeper who must be stationed at the tanks to which the fountain's pipes return if he wants to produce, or prevent, or change their movements in some way…” (ap. 141 p. 101).
That is exactly the role of the mind: to provide what the body lacks—reason, understanding, and the will. According to Descartes, the mind is “A thing that thinks...A thing that doubts, understands, affirms, denies, is willing, is unwilling, and also imagines and has sensory perceptions” (CSM 83, 28). The mind is the thing which animates the mechanical body towards an intentional goal. Pulling your hand away from a fire is merely a reflex; it takes the mind to hold it there for warmth. Staying alive, seeking food, and breathing are all automatic activities of the body; it is the mind which directs these energies towards greater projects (like philosophy).
Descartes thinks humans are an inseparable mix of mind and body. To him, it’s obvious we have a thinking mind that controls the body. However, he shows that they are not independent: I am not merely present in my body as a sailor is present in a ship, but [...] I am very closely joined and, as it were, intermingled with it, so that I and the body form a unit. If this were not so, I, who am nothing but a thinking thing, would not feel pain when the body was hurt, but would perceive the damage purely by the intellect, just as a sailor perceives by sight if anything in his ship is broken. (CSM 116, 81) Our mind is not just along for the ride; it has a very real stake in the well-being of the body. Damage to the body manifests as suffering to the mind, and likewise, the needs of the mind direct the course of the body. This intimate relationship is what we mean by “mind-body union.”
Descartes has raised three categories: beings of pure mind, pure body, or mind-body unions. Do animals fit into any of these? I will present evidence to show that none of them are completely satisfying. This should motivate us to find an alternative solution.
First, animals are not beings of pure mind. We don’t even believe that we are beings of pure mind. We know this on the basis of perceiving our body and perceiving that other humans have bodies. We see this of animals too, such that we have no reason to think that we have bodies while animals don’t. Because animals must at least have bodies, they cannot be beings of pure mind.
Animals also aren’t quite beings of pure body, at least in the strong Cartesian sense. The Cartesian mind is indivisible—the mind can’t be conceived as independent parts (CSM 120, 86). So, if animals lack minds, they must lack all of the faculties reserved for the mind. This struggles to explain why some animals exhibit intelligent behavior, such as puzzle-solving. In humans, puzzle-solving is guided by conscious mental effort engaging will, reason, and understanding—the faculties of the mind.
New Caledonian crows demonstrate puzzle-solving abilities. In a 2019 study, the birds completed multi-step puzzles requiring them to use a tool to retrieve a second tool, which would finally access the food reward (Gruber et al., 2019). Figure 1 illustrates the tasks.  For example, in Experiment 1-A, the crow needed to retrieve stick I to poke-out stone II-left while avoiding the useless task of getting stick II-right. Only once the crow had the stone could she drop it into box III to release the food reward. The crows were able to solve this puzzle. To test whether the solutions were rote, the researchers later switched up the steps so that previously successful tasks became useless tasks. For instance, in Experiment 2-C, the crow must retrieve the stone and directly place it into the final box. Using an intermediate step would consume the tool and make the puzzle impossible. The crows solved this, too. Because they realized the shortcut without simply repeating past solutions, it seems that the crows understand the role of the sticks and stones in the puzzle. This suggests that the crows have built a mental model of the puzzle and employ the faculties of the mind to solve it: the will to pursue an unseen goal, even across multiple steps; the understanding of each task; and the reasoning needed to piece these steps together.
If we thought animals were just mindless automata, then we would not expect them to solve puzzles like this without extensive trial and error. If they were acting from reflex alone, they would require conditioning to learn each step. Notably, they would easily be tricked by distractor steps which trap them into misapplying their conditioning. The crows’ success eludes this expectation, so the pure Cartesian body is an unsatisfactory explanation.
But what if we extend Descartes’ notion of body to be so featureful that it captures intelligent behavior without necessitating mental experience? This position denies that puzzle-solving requires any of the faculties we’ve reserved for the mind. So, perhaps when the crows encounter food, it triggers an enormously complex series of reflexes in the body which drive them to inspect the layout, accumulate information, and execute a pantomime which happens to solve the puzzle—all without using some workspace afforded by the mind.
The problem with this view is that it struggles to explain why we use mental faculties for puzzle-solving if animals don’t. This is challenging because, although animals differ from us in superficial appearance, most underlying systems like the nerves and the brain are quite similar to ours because they have common evolutionary origins. Without evidence that animal brains approach information processing in a fundamentally different way, this extended pure-body view raises more questions than it answers. That makes it unsatisfactory.
There is one remaining category: Could animals be Cartesian mind-body unions? Again, this is subject to the indivisibility of the Cartesian mind. So, if animals were mind-body unions, they should have all mental faculties available to them. Assuming their minds are coupled to their bodies in the same capacity as ours, we should expect animals to think and behave just like us. Using our intellect, humanity has built culture and civilization. We should at least see hints of these developments in animals: dogs chatting about the news, birds conducting experiments on gravity, chimpanzees writing their memoirs. As fellow sapients, they should also want for us to acknowledge them as peers (if only to halt the deforestation of their homes). However, we have not seen evidence for any of these, which makes this explanation doubtful.
What if their bodies were not paired in the same way as ours, such that their fully-capable minds are trapped in incapable bodies? This view is also problematic because it allows for extravagant possibilities. Perhaps my chair has a full Cartesian mind, but lacking a mouth it cannot protest as I sit and eat unhealthy snacks. Perhaps with each sip of water I inadvertently extinguish entire civilizations. The view that full minds can generally exist without means of detection leaves open the possibility that everything has a mind. That also seems doubtful.
If animals are not pure minds, pure bodies, or mind-body unions, then what are they? Let’s turn to science and try to update Descartes’ model.
We know that the mind is localized in the brain. This is because thoughts appear to be encoded by brain activity, such that there is a mapping of specific thoughts to specific brain states. Haynes et al. (2007) asked participants to decide freely whether to push a button with their left or right hand and to withhold that decision for some variable delay unknown to them. The researchers were able to use brain scans collected during this delay to successfully determine which hand they chose. This suggests that intent (the will) is stored in the brain. Other thoughts which comprise the mind could reside there as well.
We also know that brain activity precedes thought, such that there seems to be a causal connection between this activity and our conscious perception of ideas. Soon et al. (2008) asked subjects to press a button with their left or right hand whenever they wished, but immediately once they decided. Most subjects reported making their decision within one second of pressing the button. However, brain scans were able to predict which hand they would use up to 10 seconds before the act. This suggests that thoughts are physically originated by the brain long before the idea is consciously realized by the mind.
There are two ways we can update Descartes’ mind-body model with these observations.
Importantly, the physical brain is the primary driver in both models: its state encodes ideas, its state-transitions move ideas according to reason, and its interaction with memory forms understanding. This activity is then interpreted as consciousness in different ways by the two models.
We should accept mind-as-process. In both, the explanatory force comes from the brain, whose activity yields the intelligent behavior we externally observe and the mental experience we internally perceive. In mind-as-process, the brain is all there is. But in mind-as-soul, we retain an “observing soul” which serves no function. Things that have no function have no effects, and things that have no effects are unobservable. Since we want generalizable knowledge about the mind, we prefer testable theories—and an unobservable soul is not testable. Therefore, let’s adopt mind-as-process because it is the more direct explanation.
Mind-as-process neatly explains those animal behaviors which confounded the Cartesian categories. Unlike pure bodies, animals can display intelligent behavior if they have the right brain activity for that mental experience. Crows might combine neural regions that handle spatial imagination, causal reasoning, and memory to create a mental experience that can solve puzzles. Yet, unlike Cartesian mind-body unions, animals can have different mental experiences than humans. Since crows have different brains than us, their overall experience is different. Perhaps their first-person view is more primitive and hazy. Perhaps they have no concept of language, and only think in imagery. These could explain why they haven’t yet developed a civilization. In any case, mind-as-process offers flexibility in allowing physical differences to define behavioral differences, while also encouraging rigorous investigation as to why those differences impact behavior.
There’s one worry: if the brain completely explains intelligent behavior in animals, then why should we suppose they need minds? This objection marks the return of the pure-body nativist. They hold that any complex body is capable of complex behavior, but the human brain uniquely turns that into consciousness. Before, we tabled this position because it couldn’t identify what was missing in animals. But now that we’re making a positive account, we’re held to that same standard: why should we think that animals are capable of minds?
Accepting that animals have a first-person mental experience has far more explanatory power than seeing them as mechanical bags of reflexes. The latter view purports that our pets play with us simply because their bodies are stimulated in some way; that they engage in a game of fetch just because we’ve pushed the right buttons to load up an instinctual program. Although describing these behaviors as enormous sets of reflexes is certainly possible, they are much more easily explained if we see animals as willful agents, driven by subjective experiences like excitement and enjoyment. Because we know subjective mental states exist from our own experience, and because extending them to animals explains their behavior simply and directly, we should accept that animals can have mental states. This makes mind-as-process the best explanation available.
Mind-as-process means that animals have minds, insofar as it is a process of the body. This explanation rejects the traditional Cartesian categories because it allows animals to have mental experiences, but also doesn’t expect them to have a complete intellect stemming from an indivisible, unobservable soul. Since mental experience arises from brain activity, and because the brain is determined by the body, different types of bodies will result in different experiences of mind.
These experiences can vary widely in degree and diversity. We humans have no concept of echolocation, while dolphins and bats have dedicated structures for it. It’s possible that they have a unique mental experience associated with echolocation which, for all we know, could be just like “seeing.” At the same time, they don’t have the same prefrontal cortex that we do. So while we may naturally engage in an activity like playing chess—involving intense focus and step-by-step thinking—they might struggle to conceive of outcomes that are multiple steps into the future.
We originally set out to learn what animals are, but we’ve discovered a framework that can explore so much more. In raising questions about how animal biology relates to their behavior, we’ve challenged ourselves to examine our own experience and what it means to have a mind. We’ve learned that the mind is best explained as a physical process. This unlocks many interesting upshots. Perhaps machines could have the right software that leads to mental experience. Maybe minds can be frozen and stored. Maybe if the mind is just part of the body, teleporters are a safe technology. We will only learn more about these possibilities as we discover exactly how consciousness emerges from biology. But in the meantime, we at least know this: when Rover trots up to play, it’s because he’s genuinely happy to see us.
Descartes, R. (1998). Meditations on First Philosophy (J. Cottingham, R. Stoothoff, & D. Murdoch, Trans.). Cambridge University Press. (Original work published ca. 1641)
Descartes, R. (1995). The World And Treatise on Man (J. Cottingham, R. Stoothoff, & D. Murdoch, Trans.). Cambridge University Press. (Original work published ca. 1633)
Gruber, R., Schiestl, S., Boeckle, M., Frohnwieser, A., Miller, R., Gray, R. D., Clayton, N. S., & Taylor, A. H. (2019). New Caledonian Crows Use Mental Representations to Solve Metatool Problems. Current Biology, Volume 29 (Issue 4), 686-692.e3. https://doi.org/10.1016/j.cub.2019.01.008.
Haynes, J., Sakai, K., Rees, G., Gilbert, S., Frith, C., & Passingham, R. E. (2007). Reading Hidden Intentions in the Human Brain. Current Biology, Volume 17 (Issue 4), 323-328. https://doi.org/10.1016/j.cub.2006.11.072
Soon, C. S., Brass, M., Heinze, H., & Haynes, J. (2008). Unconscious determinants of free decisions in the human brain. Nature Neuroscience, Volume 11, 543-545. https://doi.org/10.1038/nn.2112