Philosophy

5

LECTURE: Introduction to materialism

The basic idea

We’ve looked in some detail at two versions of dualism, Aristotle’s and Aquinas’s hylemorphic dualism, and the Cartesian dualism of thinkers like Descartes and Malebranche. Now we turn to the main competitor to dualism, namely materialism. We might define it as follows:

Materialism: the view that that all reality is fundamentally material in nature, and in particular that all mental phenomena are reducible to (or at least supervenient upon) material phenomena (such as processes in the brain and nervous system)

Please forgive the technical term “supervenient,” but it has become common enough in contemporary philosophy of mind that a brief explanation is needed. To say that X is supervenient upon Y is to say that there couldn’t be any difference in X without some corresponding difference in Y. Materialism is sometimes formulated as the claim that mind supervenes on matter in the sense that there could be no difference in what is going on in a person’s mind without a corresponding difference in what is going on in his or her body.

“Materialism” here is obviously being used as a name for a metaphysical theory. It is different from “materialism” in the sense of an excessive interest in money and other material things (as in Madonna’s song “Material Girl”).

An anti-Cartesian anthem?

Sometimes philosophers who would traditionally be called “materialists” prefer the term “physicalism,” one definition of which would be:

Physicalism: the view that everything that exists or occurs can be described completely in the vocabulary of physics

Here, I guess, the theme song, for you fans of pop music history, would have to be that classic Olivia Newton-John tune.

“Let’s get physical!”

The idea of physicalism is to tighten up what the materialist means, or should mean, by saying that everything is “material.” Physicalism says that what is material is what can be defined in terms of the fundamental entities and forces that the science of physics, specifically, talks about: protons, electrons, gravity, and so on.

One problem with this is that it’s not clear what it rules out, since physics isn’t complete. Physicists don’t claim to know everything there is to know about the physical world. Maybe physics will one day reveal that the nature of matter is very different from what current physics says it is.

Another problem is that physicalism arguably turns out to be too restrictive. There are many things that are clearly real and yet cannot be described entirely using just the vocabulary of physics. For example, if you try to describe the differences between a dog and a dollar bill in terms of nothing more than the relationship between the particles that make them up (and without making use of specifically biological concepts or economic concepts), you will find it impossible. There is just more to even the material world than can be described solely in terms of particles in motion, etc.

For this reason, philosophers who would at one time have used labels like “materialist” or “physicalist” these days often prefer to go instead by the label “naturalist.” We might define the key term here as follows:

Naturalism: the view that everything that exists or occurs is part of the natural world studied by empirical science

The idea here is that what is real is what is part of the natural world, and what is part of the natural world is whatever science studies. It needn’t be physics, specifically, that reveals what is real, so the view isn’t as restrictive as physicalism. But, naturalism says, if something is real, its existence should be revealed to us by some empirical science, such as chemistry, biology, or what have you. (For our song here, let’s go with Aretha Franklin’s “A Natural Woman.”)

“You make me feel…!”

The basic idea, then – whether you want to call it materialism, physicalism, or naturalism – is that the mind is ultimately like hydrogen and oxygen, rocks and trees, dogs and cats and other physical objects studied by physics, chemistry, biology, etc. It is made of the same basic stuff and governed by the same basic laws. It is not an immaterial or non-physical substance like Descartes’ res cogitans. But exactly what kind of physical thing is the mind? Here materialists have given different answers.

Behaviorism

Behaviorism is the version of materialism that says that any mental state (such as a thought, a sensation, a memory, or whatever) can be entirely analyzed into patterns of bodily behavior or dispositions toward such behavior. There’s nothing more to a mental state than that.

For example, it holds that to have a sensation of pain is nothing more than to have a tendency or disposition to exhibit behaviors such as flinching, yelling “Ouch!,” crying, massaging an injured body part, and the like. To have the thought that it is raining is nothing more than to have a tendency to exhibit behaviors like saying “It’s raining,” going to the closet and grabbing an umbrella, etc. And so on for all other mental states. They can be entirely defined in terms of tendencies to exhibit various behavior patterns.

The reason this is a version of materialism might be obvious. If we think of behavior as just bodily movements, then to reduce the mind to a set of behavioral tendencies is to reduce it to a set of physical properties of a physical object, the body. (OK, one more theme song, this time from Björk.)

“Human behavior!”

“Behaviorism” is a term you might also have heard in a psychology class, and the view we’re talking about here is related to that, but not exactly the same. In psychology, behaviorism is primarily a matter of methodology – it says that the way to study the mind is to focus on what everyone can observe, which is people’s behavior. In philosophy, behaviorism is a view about metaphysics – it claims that all that exists where the mind is concerned is what everyone observes, which is behavior.

Behaviorism has long been out of favor with materialists. There are a number of problems with it, some technical. One objection that both common sense and philosophical critics alike would raise against it is that it seems obvious that there is more to mental states than just the behavior associated with them. There are also what we called, earlier in the semester, the qualia associated with conscious experience – the subjective, first-person features of an experience directly knowable only “from the inside,” as it were.

For example, when you are in pain, in addition to the behavior you exhibit, there is the feel of the pain. If someone is a good enough actor, he or she might actually be feeling no pain at all, but behave, perfectly convincingly, like someone who is in great pain. Or he or she might be feeling great pain but behave, perfectly convincingly, like someone who is in no pain. So, the qualia associated with pain are something over and above just behavior.

The identity theory

The “identity theory” is the sort of view people usually think of when they think of materialism, and while it too is not the currently most popular view among materialists, it is worth looking at in some detail. The view can be defined as follows:

The identity theory: the view that mental states and processes are identical with physical states and processes within the brain and central nervous system; in short, the mind = the brain

It’s important to understand what this view is saying, because it’s a bolder claim than you might realize. The identity theory is saying that your thought about what you had for dinner last night (for example) is identical to the firing of a cluster of neurons. But it isn’t just saying that a cluster of neurons firing caused your thought about dinner. That would not by itself be enough to make the view a version of materialism. After all, Descartes would agree that a thought might be caused by neurons firing.

No, the identity theory is making a much stronger claim than that. It is saying that your thought is exactly the same thing as the cluster of neurons firing. Thus, if you could observe the firing of the neurons, you would literally be looking at a thought. That’s what a thought really looks like. That should sound strange; the identity theorist admits that it sounds strange, but claims that we should accept it anyway.

This is your brain on drugs. And this is your mind on materialism.

Arguments for the identity theory

Why? There are at least five considerations often raised in defense of the identity theory:

1. Causal interaction between mental states and physical states is better explained on the hypothesis that mind and brain are identical than on the hypothesis that they are distinct

The idea here is that Cartesian dualism faces the interaction problem, which arises because Descartes takes mind and body to be two radically different kinds of substance. But if we think of the mind as the same thing as the brain, then the mind can be said to interact with the rest of the body the way any other two physical objects might interact, and the interaction problem disappears.

2. The detailed correlations between mental phenomena and neural processes that neuroscience has uncovered are just what we would expect if the identity theory were true

Here the claim is that if the mind was an immaterial res cogitans, as Descartes says it is, then we wouldn’t expect that changes to the brain (such as drunkenness, brain damage, etc.) would have as dramatic an effect on the mind as they do.

3. Individual human beings appear to have purely material beginnings and to develop via purely material processes; so the end result, including the mind, must be purely material

4. Animal species, including human beings, appear to have purely material beginnings and to develop via purely material evolutionary processes; so, the end result must be purely material

These two arguments appeal to the idea that you can’t get more out of a process than you put into it. Now, the identity theorist claims that human beings, both as individuals and as a species, have origins that are entirely material (a fertilized ovum in the case of the individual, and primitive biochemical processes in the case of the ancestors of the species). Furthermore, the argument says, the path through which we got from these origins to mature human beings is also purely material (cell division and the like in the case of the individual, mutation and natural selection in the case of the species). So, the outcome of these processes – including our thoughts, experiences, etc. – but be purely material.

5. Ockham’s razor favors materialism as the simpler hypothesis

This is really the key argument. The first four arguments don’t decisively show that the mind is material (and are not claimed to show that). They at most increase the plausibility of the claim that it is. The crucial question is whether there is any aspect of the mind that cannot even in theory be explained in materialist terms – such as qualia, intentionality, or rationality (which, as we saw earlier in the semester, are the aspects of the mind that philosophers tend to argue about the most).

If materialism can indeed explain all three of these aspects of the mind, then, the argument goes, we would not need to postulate a non-physical res cogitans or the like. And the principle of “Ockham’s razor,” which tells us to cut away needless hypotheses, would then tell us to opt for the identity theory over any form of dualism.

So, the debate over the identity theory – and over materialism more generally – is ultimately going to be a debate about whether materialism really can explain all three of those problematic aspects of the mind. We’ll see how materialists have attempted to explain them as we look at materialism in more detail over the next few weeks. In the meantime, here are some optional YouTube videos explaining in more detail some of the main concepts we’ve been talking about:

John Wilkins on Physicalism and Materialism:

https://www.youtube.com/watch?v=8Xn5w_KcdII

Closer to Truth on Is the Person All Material?:

https://www.youtube.com/watch?v=gjhx7k0T2J8

Identity Theory:

https://www.youtube.com/watch?v=owkDAtUsvSA