Cartesian Dualism: A Functionalist Critique

I would like to begin by saying that I have a lot of respect for Rene Descartes. He was one of the most brilliant philosophers of all time, and his emphasis on epistemological rigor is to be admired. However, this is not to say that his views were correct. In this post, his dualist belief in an immaterial mind that is separate from the body will be challenged. People in general have an intuitive belief that we are more than just our bodies or brains, and many have found dualism an appealing and convincing view for that reason. After examining his classic argument for dualism, I will examine some of the reasons that dualism is appealing, and why one should not be so quick to believe it.

Descartes laid out his case for dualism in his classic book Meditations on The First Philosophy. His main argument is found in the sixt meditation, but builds on arguments from previous meditations, particularly the second and third meditation. 

The gist of the argument is that it is possible for you to doubt that you have a body. However, it is not possible to doubt that you have a mind, because doubting is a type of thought and for you to be aware of thoughts makes it self-evident that you as a mind exist. Since the body  has the property of being doubtable, but the mind cannot be doubted, they possess different properties. Since they possess different properties, they cannot be said to be the same thing. So, Descartes concluded, the mind must be a separate entity from the body. This invokes a logical principle that later would come to be called the Indiscernibility of Identicals Principle by Gottfried Leibniz. Simply put, the principle states that if two things are identical then they are indiscernible from each other. Again, since the mind and brain appear to have different properties, they are discernible, and thus cannot be identical since identical things are indiscernible. Descartes said that mind is made of mental stuff, or res cogitans, and matter is made of res extensa.

The problem with this argument is that he concludes that just because the mind is conceptually distinguishable from the brain, that it is altogether a separate entity. Take the other organs besides the brain for example. Digestion is a different concept from the digestive system. Breathing is different from the lungs. Pumping blood is different from the heart. The functions of these organs are conceptually different from the organ that does them. Thinking is what the brain does, just as the other organs perform their functions. I agree with Descartes that the mind and the brain are conceptually different, but this conceptual difference does not make them separate entities no more than breathing is a separate entity from the lungs. It amounts to a misapplication of the indiscernibility of identicals principle.

How do we know that the brain and mind are so intimately connected? After all, couldn't the brain be the mechanism by which some immaterial mind or soul acts through? As is commonly known in modern times, brain damage or brain disease can severely affect the way you think. Damage to the Wernicke's or Broca's area can severely damage your ability to speak. Imbalances in neurotransmitters can cause various mental illnesses. Damage to the visual cortex can result in blindness despite perfectly healthy eyes. Just as well, we know that conscious awareness seems to come after brain activity, as shown by experiments from Benjamin Libit in the 1980s.¹ This shows that decisions were detectable in the brain milliseconds before there was conscious awareness. Milliseconds may not sound like much, but consider that nuclear explosions happen on an even shorter time scale of microseconds and make quick work of anything near the fireball. Besides, it is not how long brain processes occur before there is conscious awareness, but the fact that brain processes occur at all before conscious awareness that shows mental states are on metaphorical puppet strings, with the brain being the puppet master.

It follows then that the mind, or rather, mental states can be thought of in terms of what they do, or their function. Functionalism is technically agnostic on the ontological matter of whether or not mental states should be thought of as separate from brain states, in contrast to views such as type-type identity theory, or reductive materialism, which holds that brain states are identical to mind states, or eliminative materialism which is the radical thesis that there are no mind states and that our "folk psychology" terms (thought, feeling, belief, desire) are just names that were invented to describe behavior of people with ignorance to neuroscience. However, functionalism fits well with a materialistic view of the universe, and generated the dominant theory of cognition, the computational theory of mind. It might be worth noting that the computational theory is not a single theory, but rather an approach to generating theories of the mind. The computational theory of mind sees the mind as an information processing machine, and there are competing views of exactly how this computation works. 

In the functionalist view, different mind states can be seen as functional states of the brain that could conceivably take place in something besides a brain.² Research into artificial intelligence is a huge part of this; artificial intelligence research attempts to take the models of human cognition from cognitive psychology and implement them in computers. There has been limited success, such as the feats of the supercomputers Deep Blue and Watson. There are doubts however that a computer could ever be as complex as a human mind, or be capable of genuine emotion even if it could think.

Another reason for a materialist to support functionalism is the fact that different brain states can represent the same mind state, not just between different people who obviously have different physical brain states for an identical thought, but within the same brain. I myself took this as evidence of dualism previously, but now believe it to be compatible with materialism if one adopts a functionalist view.

You might be thinking hold on a minute! What about explaining qualia, or the first person, subjective awareness of the world? Philosophers of mind such as David Chalmers have proposed that even if we understood the computational aspects of the mind, and had a complete neuroscience, that we still would not be able to explain this phenomenological aspect of the mind. Chalmers refers to this as the "hard problem" in explaining consciousness. He has proposed that we must conclude there is more to the mind than just matter, and supports a different type of dualism from the substance dualism of Descartes called naturalistic dualism or property dualism.³ I do not think that proposing a dualism is a very helpful solution to the hard problem of consciousness. Concluding that there is an immaterial mind, or some mystical aspect of matter besides physical properties, is a cheap and quick solution, but it raises more problems in the end. Just as saying God created the universe or launched the big bang leads to more questions of what the nature of God is, how he accomplished such a feat, and where God came from, so too does the dualist answer to the hard problem raise questions such as how something immaterial could control something material, or how physical processes in the brain cause immaterial properties to emerge from matter. Rushing to a dualist solution then makes the problem unsolvable in principle, since immaterial things are by definition unobservable.

I also question the validity of the concept of immaterial substances. I believe, as per the pragmatic maxim, that the meaning of a word consists in its practical or observable consequences (this at least applies to nouns and verbs). To what exactly does the concept of res cogitans refer? If the idea of immaterial or mental substance refers to our phenomenolgical awareness, then that is tantamount to saying that mental substances are the mind, which is made of mental substance. It is rather circular. I agree with Thomas Jefferson when he wrote, "To talk of immaterial existences is to talk of nothings. To say that the human soul, angels, god, are immaterial, is to say they are nothings, or that there is no god, no angels, no soul."⁴ I do not think I can prove beyond a shadow of a doubt that only material things exist, but I think my objections to the concept of immaterial substances are sufficient to warrant accepting materialism as the best view of reality and of the mind. It is possible however for a functionalist to conceive of mental states as being an immaterial property of matter or one that "emerges" from the physical processes of the brain, but my main quarrel is with Cartesian or Substance dualism.

In conclusion, I have attempted to show that Descartes was correct in saying that the mind and brain are different, but only conceptually and not ontologically. I have also attempted to show that functionalism and the functionalist computational theory of mind are better ways to think about the mind-body problem and that being a materialist need not warrant an overly reductionist or eliminativist viewpoint. Finally, I have attempted to show that rushing to viewpoints that invoke concepts such as immaterial substances do little but make already difficult and mysterious problems such as the origins of the universe and the nature of consciousness that much harder, or perhaps impossible, to solve. It is better to admit of uncertainty and make incremental progress than to rush to quick and easy answers; as Neil DeGrasse Tyson said, “There are times, at least for now, when we must be content to love the questions themselves.”

References:


1. Libet, B., Gleason, C.A., Wright, E.W., Pearl, D.K. (1983). Time of conscious intention to act in relation to onset of cerebral activity (readiness-potential). The unconscious initiation of a freely voluntary act. Brain. 106 (3):623–642.
2. The Conscious Mind: In Search of a Fundamental Theory (1996) by David Chalmers 
3. A Historical Introduction to the Philosophy of Mind by Peter A. Morton, Chapter 11, pg 297-334
4. Jefferson's letter to John Adams, from Monticello, August 15, 1820.

Suggested Further Reading:
1. How The Mind Works by Steven Pinker
2. The Blank Slate by Steven Pinker
3. Descartes' Error by Antionio Damasio

4. Chapter 4 & 5 of A Historical Introduction to the Philosophy of Mind by Peter A. Morton