In philosophy, there exists a view known as dualism, where consciousness and the mind are believed to be fundamentally different from the physical. There is substance dualism, argued by Descartes, that declares that minds and bodies are two different substances entirely. There is also property dualism, argued by Brie Gertler, that declares that consciousness and therefore experience do not consist of merely physical properties. Then there are those views that are not dualist. Of these, I will be discussing D.M. Armstrong’s functionalism, which describes a mental state as “characteristically, the cause of certain effects and the effect of certain causes” (82). In this way, a mental state like hunger is characteristically an effect of lack of food, and characteristically the cause of getting up to find something to eat. I see functionalism as the most compelling because it handles such issues as solipsism, which Cartesian dualism struggles with, and mental causation, which property dualism struggles with by having to come to philosophically undesirable conclusions (epiphenomenalism, overdetermination, denial of causal closure) to understand it. Moreover, I see experience as not beyond the physical; if one was able to grasp all the physical, they would grasp the experience. A completely physically knowledgeable person may gain a new skill through doing something new, but they already know all there is to know about the experience.
First, we will begin with Cartesian dualism. Descartes comes to a dualist conclusion by setting off on an epistemological journey to set a firm foundation for all knowledge. The key to laying this firm foundation is to distill the things we think we know down to the things we are absolutely certain we know. Descartes does this through a series of doubts. In this series, Descartes goes through each of his foundational beliefs; if it can be doubted at all, it shall be put aside. After all these doubtable beliefs have been put aside, only the certain will remain, and that will be what we can build knowledge off of.
Descartes’ first type of foundational belief is that his senses give him accurate information about the world and what it is like. The doubts for this foundational belief are not difficult to find: sometimes one mishears things; sometimes one sees refracted light. In this way, one’s senses routinely deceive them. We now know sense-based perception is not certain and it can be put aside. That first belief is then altered to remove doubt, creating Descartes’ second type of foundational belief that at least in good conditions (nothing loud preventing you from hearing correctly, no water refracting light), the senses provide accurate information when working together. This too is easily doubtable, Descartes notes, given that dreams, hallucinations, and mental illnesses all cause the senses to work together, in good conditions, to deceive their users. The senses are put aside. Descartes continues the method, going now to his third type of foundational belief, that at least his intellect gives him knowledge of the general types of things, including conceptual truths like mathematical facts. Even this, Descartes argues, is doubtable. He conceives of an evil genius that could be deceiving him and leading him to believe inaccurate conceptual truths. Thus, the intellect’s ability to discern conceptual truths is put aside with the senses’ ability to discern environmental truths.
What is left of Descartes’ knowledge after the senses and the ability to see conceptual truths are gone? Only his mind. Descartes is only certain that he—a thing that thinks—exists. This thing that thinks that Descartes is sure exists is therefore a distinct type of thing, one that is knowable with certainty through introspection. It is also unextended, meaning it doesn’t take up measurable space. This kind of unextended, thinking thing, knowable with certainty via introspection shall be called a mind. Bodies, on the other hand, are things that are extended, unthinking, and knowable via perception (and therefore never knowable with certainty). Descartes’ view is aptly called substance dualism, as it recognizes two distinct substances: minds and bodies.
With substance dualism, there arrive some philosophical problems. I will be focusing on the two most glaring to me, the first being the issue of other minds. If minds are only knowable through introspection, what possible reason does one have to believe that anybody else has a mind? A situation where the existence of other minds is not certain is troubling not only because it challenges our existing views, but it also might cause moral dilemmas. If nobody else has a mind, shouldn’t the world bend to the satisfaction of my mind? I should steal what I want and kill who I want; nothing that is definitely thinking will suffer. The second most glaring issue is that of mental causation. If minds and bodies are so fundamentally different, how do they seem to interact constantly? When I’m hungry (an issue of the mind), I put my philosophy reading down and go get the Snickers sitting on my desk (undeniably an issue of the body). Cartesian dualism struggles with these two issues, solipsism and mental causation. Functionalism does not.
Armstrong presents his functionalism by first presenting identity theory. This is the theory that the mind is identical to the brain. Every mental state is just a brain state. Let’s use an example: there is a well-documented neurological connection between dopamine and joy. An identity theorist would therefore say joy is dopamine.[*] Armstrong sees this theory as a “perfectly intelligible one…once we achieve a correct view of the analysis of mental concepts” (82). Armstrong’s mission then is not to firmly rule on the correctness of identity theory, but rather to “make the way smooth” for it and make it seem plausible (82).
Armstrong is able to accomplish this by reconceiving of mental states as things that follow from certain inputs, and lead to certain outputs. He compares this to the meaning of the word poison. A poison is defined as any substance that causes certain effects, like hurting the body in a certain way enough to potentially kill a person. Similarly, hunger can be defined as “a state of a person or animal that characteristically brings about food-seeking and food-consuming behavior by that person or animal” (82). Any mental state can theoretically be defined in this way, as flowing from inputs to outputs. Take my anger at a friend of mine: it flows from the inputs of my perception of his doing something wrong, and it characteristically leads to me the output of confronting the friend. Inputs can also be brain states themselves. The mental state of utter despair a clinically depressed person feels is an effect of abnormal brain chemistry (an input) and the utter despair is also a cause for them to pick up the phone and text their friend to ask if he knows any good clinical psychologists (an output). Next, we will discuss a new kind of dualist, who has found an issue (or so she thinks) with functionalism: aren’t mental states more than just the effects of causes and the causes of effects? What of the experience of a mental state?
I will be using Gertler to stand for such dualists, known as property dualists. These dualists believe that the mental has different properties as the physical. In Gertler’s words, “conscious experience is neither constituted nor necessitated by structural-dynamic phenomena” (6). The structural-dynamic phenomena are enough to exhaustively constitute physical states, but “conscious experience” is of fundamentally different properties. Gertler is arguing for the qualitative nature of the mental. Since the mental is qualitative, she argues it cannot be understood exhaustively through the physical sciences. Having set up her thesis, Gertler begins to defend it with a couple thought experiments. For Gertler, both of these thought experiments come to the conclusion she is looking for: there is something about experience, even if we can’t put our finger on it, that isn’t structural-dynamic (or physical, as most people would say).
The first of these experiments is known as the knowledge argument. The thought experiment centers on Mary, a genius neuroscientist living in the future. Being so talented and futuristic, Mary has learned everything about color vision, but she has never seen any colors. She knows the wavelength of red, and she knows the neural effects of seeing red. Yet, as the example goes, she will learn something new when she sees red. She will likely even admit this, exclaiming “Oh, this is what it’s like to see red” (9). The second thought experiment asks us to imagine a zombie that has all the exact same physical characteristics of us down to every single atom, but isn’t conscious. The implication of the exercise is that we can easily imagine this, and we therefore conceive of consciousness as not merely physical.
I don’t like either thought experiment,[†] but the gist is easy to get. Each thought experiment is trying to get us to agree that consciousness is much more than the physical by taking the physical to the extreme. Just because all the physical is there, that doesn’t necessarily mean consciousness is, the zombie theorist tells us. Just because you know all the physical doesn’t mean you know the conscious experience, the Mary theorist tells us. Unlike Cartesian substance dualism, this property dualism seems able to handle the concept of other minds. However, it still struggles with mental causation, the issue of how the mental can cause the physical.
To understand the issue of mental causation, let’s look at the example we’ve already mentioned a couple times: hunger. A hungry person has a physical state of lacking, and a mental state of hunger. That person will then contract his muscles in the right way to go get food, and as he eats, he will feel satiated. Mental state #1 is hunger; physical state #1 is energy-deficient cells (and other physical features of hunger, maybe cortisol or adrenaline); mental state #2 is satisfaction; physical state #2 is cells beginning to produce energy from the food being processed (and other physical features, maybe dopamine releases). What caused physical state #2? According to the principal of causal closure, each physical event must be able to be fully explained by a physical cause, so physical state #1 must be to blame. What then of mental state #1? The identity theorist says that mental state #1 must then have been included in physical state #1. Armstrong’s functionalism is in line with this (or at least proves its intelligibility). What does the dualist say of mental state #1? The dualist has 3 options that maintain mental state #1’s distinctness from physical state #1.
- Mental state #1 had no physical effects, and mental states never have any physical effects (this is called epiphenomenalism).
- Mental state #1 caused physical state #2, but so did physical state #1. This is overdetermination.
- Causal closure is not a true idea.
Gertler essentially arrives at the third. She argues that causal closure relies on an “exhaustive” nature of physical causality. This is a much higher bar than just what scientists have arrived at in the study of structure and dynamics. Therefore, the physicalists require the same amount of armchair reasoning to defend their theses as dualists do theirs. The debate really comes down to what a person finds conceivable, she says. Dualists require conceptions of subjective consciousness and (seemingly) zombies. Physicalists require conceptions of the structural-dynamic as being able to exhaustively explain all physical phenomena, which has not yet been proven.
I stand with the functionalist, and I also happen to stand with the identity theory it supposedly enables, though I won’t get into the latter. Functionalism doesn’t struggle with the solipsism Cartesian dualism enables. Functionalism also handles mental causation nicely as it is literally defines mental states causally (the effects of certain causes and the causes of certain effects). By contrast, dualism’s handling of mental causation is not philosophically desirable in my opinion. Let’s go through the 3 options for a property dualist to understand mental causation while maintaining the distinctness of the physical:
- Epiphenomenalism goes against much of what we consider to be true, like that our hunger motivates us to eat or that our sadness causes tears. Epiphenomenalists may have good solutions to this, but at best it is an idea that runs contrary to everything most people believe about the mind and its ability to influence our actions.
- Overdetermination implies that only one of either the physical or the mental is really necessary. Without violating causal closure (meaning the physical is necessary), this renders the mental causally unnecessary. It may still have causality, but it doesn’t have importance. Again, this is unsettling. Shouldn’t hunger be the motivating force of us getting food? Not just an entirely needless feeling?
- Denying causal closure—if causal closure is denied, then the physical and the mental must both be needed for physical effects. This seems incorrect as well. Take hunger again: if food-seeking requires both physical lacking and hunger, then how come things that don’t have a mental (like bacteria) have so many food-seeking behaviors. Surely food-seeking doesn’t require the mental.
What about the thought experiments that prove dualism to be true, though? What about Mary and the zombie? The zombie experiment dies out if the assumption of conceivability doesn’t hold (and it doesn’t for me), but Mary is slightly more interesting, after we tweak the example. Let’s say there is a brilliant neuroscientist named Ann, living in a future where nearly everything is known about vision science, but cone transplants do not yet exist. Ann grows up in the normal world with normal colors, but she is just incapable of seeing red due to her not possessing the right cones. This hasn’t stopped her from being educated, and she has become a brilliant vision scientist who now knows everything physical there is to know about color vision. During Ann’s quest for tenure at the university she works at, she figures out how a cone transplant could be conducted. She finds an eye surgeon who is capable and has the transplant performed on her. Walking outside the clinic, she sees a stop sign. She is seeing red for the first time. However, I don’t believe she is learning anything new. She has gotten a new skill, the ability to see red, but I do not see what she learns. She experiences all the physical effects of seeing red for the first time, but she has expected all of them. All of the workings of her brain are just as her scientific models have predicted because she knew everything. The only thing that has changed is that she has gained the skill of seeing red and has now herself exhibited all the same physical effects of color vision that she had studied.
Cartesian dualism puts us in a place where we doubt the minds of others. Property dualism doesn’t struggle with this issue, but it does struggle with mental causation, forcing us to admit the ineffectualness of the mental, the needlessness of the mental, or the lack of physical without mental. All three of these are undesirable. Functionalism defines its mental states as existing in this causal chain, making mental causation easy while still avoiding the solipsistic potential conclusions of Descartes. The main worry about functionalism and identity theory is it leaves out the key nature of the mental as qualitative and beyond the reaches of science. The thought experiments that one could propose to prove the qualitative nature of experience involve assuming existing agreement on dualism (the zombie, who would be denied by identity theorists anyway) or the mistake of thinking that acquiring a skill is learning a fact (Mary, or even Ann). Thus, the functionalist view is the one I side with.
[*] They would probably be more sophisticated than this. A true type-type identity theorist might say something more like “joy is just the brain activity scientifically associated with joy and dopamine is clearly a part of that associated brain activity.” Upon the discovery of each new physical characteristic of the brain associated with feelings of joy, a type-type identity theorist would add that physical characteristic to her conception of joy.
[†] The Mary example makes no real sense to me. She is an incredible neuroscientist living in the distant future, in a time where literally everything physical about color vision is known. In fact, she literally knows the wavelength of red. How is it possible she hasn’t built a machine (or come across one thousands of years ago) that can produce colors based on wavelengths? We can produce many wavelengths today, and it’s quite easy to figure out which we can see by looking at them and seeing if they look like a color to our eyes. I struggle to understand this thought experiment, but I think her being unable to see red makes the whole experiment much more comprehensible. I will return to this example.
The Zombie example is even worse in my opinion. It relies entirely on the conceivability of this zombie. Conceivability is very subjective and I would doubt there is an identity theorist who would admit the conceivability of the zombie.