Doctrine of Man (Part10): Refuting Reductive and Non-Reductive Physicalism

March 11, 2020

Refuting Reductive and Non-Reductive Physicalism

In our last session we completed a look at the biblical data supporting a dualistic view of anthropology. Today I want to say something by way of a philosophical defense of dualism-interactionism. Rob Koons and George Bealer in their book The Waning of Materialism have pointed out that the physicalist view of the mind has been waning in recent years among professional philosophers. They're beginning to realize the many problems with a materialistic anthropology and are starting to move away from it. In order to appreciate the problems that materialism faces it will be helpful to draw some basic distinctions in the philosophy of mind.

Beginning with the mind, there are two fundamentally different accounts of the mind. One would be physicalism (or materialism) and the other will be dualism. Physicalism holds that there is no immaterial constituent of human being – that human beings are simply material organisms. Physicalism comes in two versions. One would be reductive physicalism and the other is non-reductive physicalism. Reductive physicalism holds that mental states are identical to physical brain states. So far as the mind is concerned, there is just the brain and its physical states. All of our supposed mental states are reducible to brain states. By contrast, non-reductive physicalism holds that while the soul or our mental states are not reducible to the brain or to physical brain states nevertheless the soul is not a real thing. Mental states are mental properties that supervene on the brain states and are ontologically dependent upon them. We can distinguish two types of properties in this regard. On the one hand there are the physical base properties that are ontologically the ground of these higher supervenient mental properties. Once all the physical properties are in place, the claim is that the supervenient properties just automatically come along as part of the package. A good illustration of this sort of supervenience is the wetness of water. Water, as you know, is H2O – just hydrogen and oxygen. But neither hydrogen nor oxygen is wet, right? So when hydrogen and oxygen are combined as H2O the property of wetness supervenes on the hydrogen and the oxygen. The view of non-reductive physicalism is that all that really exists is the brain but mental states or properties supervene on the material brain somewhat in the way that wetness supervenes on H2O. Any causal powers of the water are not due to the supervenient properties. The causal powers are due to the underlying base properties of the oxygen and the hydrogen to cause and bring about certain things. Similarly, the causal properties of the brain are its physical properties, not its mental properties.

What might be said about these two forms of physicalism? Philosophy of mind is not my area of specialization, so let me draw upon the work of a very fine philosopher of mind Angus Menuge and his paper, “Why Not Physicalism?”[1] Menuge lists several problems confronting a materialist or physicalist philosophy of mind. Menuge says,

Reductive or eliminative forms of physicalism fail to account for our mental lives. But . . . the varieties of non-reductive physicalism also fail to account for mental causation. If these [non-reductive] theories are faithful to physicalism, then supervening or emergent mental properties cannot add anything new that was not going to happen anyway, as a result of their physical base properties. If we want to account for consciousness, mental causation and reasoning, we need some entity over and above the body. This entity must be simple, have thoughts as inseparable parts, persist as a unity over time, and have active power. That sounds like a soul . . .

Let's break this paragraph down a bit. Here Menuge distinguishes between two types of physicalism. First is reductive or eliminative physicalism. Reductive or eliminative versions of physicalism are increasingly unpopular. They just don't seem to account, as Menuge says, for our mental lives because the brain on this view as a physical substance has only physical properties such as a certain volume, a certain mass, a certain density, a certain location, a certain shape, and so on. But the brain on this view doesn't have any mental properties. The brain isn't jubilant or sad. The brain isn't in pain. When your back hurts and you are in pain, it's not the brain that is in pain even though the brain is involved in the neural circuitry that gives you the experience of pain. Reductive physicalism therefore cannot account for our mental lives. Take the phenomenon of fear, for example. When you have fear, undoubtedly there is brain activity that is correlated with the experience of fear. The dualist-interactionist agrees with that. It's not as though the soul operates independently of the brain. Rather, there is an interaction with the brain in the experience of fear. But the brain itself isn't afraid. You can't reduce fear to a physical brain state even though it is correlated with neural activity in the brain. So reductive physicalism is obviously untenable. It cannot be reconciled with our mental experience.

This has led many thinkers to affirm some sort of non-reductive physicalism. The brain gives rise to supervenient or sometimes called epiphenomenal states of awareness like jubilance or sadness or pain. But there isn't any thing – there isn't any soul or mind – that has these properties. Rather the brain is the only thing that really exists and these mental states are grounded in the brain. Menuge identifies a number of problems with this view.

First of all, he points out that it's incompatible with self-identity over time. Think about it. The brain endures from one moment of time to another; the brain thus has identity through time. But it's states of awareness don't endure from one moment to the next. There is no enduring self – no “I” (capital-I) that endures from one moment to the next. This view of the self or the “I” is rather like the Buddhist view of the self. The Buddhist says that the soul or the self is something like the flame of a candle. The candle and the wick endure from one moment to the next, but the flame doesn't endure. There is a different flame at each moment of the candle’s burning. The flame exhibits a sort of continuity in that the candle doesn't go out while it's burning, but there isn't really any identity of the flame from one moment to another over time. The situation is similar on non-reductive physicalism with states of awareness. Every state of the brain at different times has a different state of awareness associated with it, but there isn't any enduring self or “I” from one moment to the next. This leads a naturalistic philosopher like Alex Rosenberg to affirm the radical position that there is no enduring self on atheism. The existence of the self, he says, is an illusion. In his book The Atheist’s Guide to Reality, Rosenberg affirms “I do not exist.” Similarly, it's an illusion that you are the same person who walked into class this morning. In fact, you are not the same person because there is no personal identity over time. If you do believe that you exist and that you are the same person who came into class this morning then you ought to reject a non-reductive physicalist view of the self.

Secondly, intentional states of consciousness don't seem to make sense on non-reductive physicalism. The property of intentionality is the property of being about something or of something. For example, I can think about my summer vacation or of my wife. Physical objects don't have these sorts of intentional properties. The brain is not about something any more than a chair or this podium is about something or of something. It is only thoughts which are of something and so have aboutness or intentionality. But on non-reductive physicalism there is no self which has states of intentionality. So intentionality is, in effect, an illusion. Again, Rosenberg bites the bullet and he says we never really think about anything. It's just an illusion that we have intentional states. He acknowledges that without intentionality sentences aren't about anything because a sentence is just a bunch of ink marks on a piece of paper and therefore not about anything. They are just meaningless marks. So he says that every sentence in his book is meaningless including that sentence! He says what good does a book like this do? Why even write it? His answer is that if looking at these ink marks on paper causes certain neural firings to take place in your brain such that your activity is altered then the book will have achieved something. But of course that achievement can't be Rosenberg's purpose in writing the book because on his view no one has any purposes for anything. I think at best he could say that he was determined to write it, and you are determined to react to it in the way that you do, but it's difficult to see here any sort of overarching purpose or significance to it. In any case, the denial of intentional states is not only contrary to experience – I mean, after all we are thinking about Rosenberg's argument, aren't we? – but this is actually self-refuting. For what is an illusion? An illusion is always an illusion of something. So an illusion is itself an intentional state. An illusion of intentionality is an intentional state. You are having any illusion of something. The view that intentionality is merely an illusion is literally self-refuting and incoherent. Again, if you think that you ever have thoughts about anything or of something then you ought to believe in the reality of the soul and to reject non-reductive physicalism.

Thirdly, free will seems impossible to reconcile with either reductive or non-reductive physicalism. On these views there is no causal connection between the sequential states of awareness. Mental states are not causally connected. The only causality is purely on the physical level and that is completely determined by the laws of nature and the initial physical conditions. There just isn't any room for freedom of the will. On this view, again, free will is an illusion. You never really do anything freely. And that flies in the face of our experience of ourselves as free agents. I can freely choose to think about certain things or to freely do certain things. I'm not simply determined by my brain states. So if you believe that you ever do anything freely then you have good reason to believe in the reality of the soul and to reject these reductive and non-reductive views of physicalism.

Menuge also points out that if we want to provide an account of reasoning we need a soul. If there is no self who reasons from premises to conclusions then we are just like a pocket calculator which is such that when you press the buttons 2, +, and 2 and then hit the equal sign button, the calculator reads 4. But the calculator doesn't reason to arrive at that conclusion. There's no reasoning going on there at all. It's just electronic circuitry firing. Again, if you think that you ever reason to arrive at a conclusion then you ought to think that you are more than just a moist robot; that in fact you are a self who does this reasoning.

Finally, fourthly, the last phenomenon that Menuge points to is mental causation. Notice that on these non-reductive physicalist views, the only arrow of causation is from brain states to brain states (represented by B and the causal connection by the arrow) and from brain states to correlated mental states (represented by the letter M).

The only causation that exists among these states is from brain state to brain state and from brain states to the correlated mental states. But the epiphenomenal mental states themselves don't cause anything. There are no causal connections between the mental states nor do they have a sort of reverse causation on the brain states. They are utterly, causally impotent. So there is no return causality from states of awareness to the brain. Why? Because there is nothing there. There is no soul. There is no mind that can exert a causal influence on the brain. On this view the arrow of causality goes only in one direction – from the brain to these epiphenomenal states as well as from physical brain state to brain state. This is incompatible with my introspective grasp of my ability to cause things. I can cause my arm to go up. I can raise my arm by thinking about it. I can do other things through thinking and therefore bring about causal effects. Menuge also discusses the fact of what's called neuroplasticity according to which thinking can actually affect the brain. If you think in certain ways it produces brain effects. There is even a kind of cognitive therapy that in some cases is more useful than drugs in changing people's behavior. If you can alter the way that the patient thinks about something, this will affect the patient physiologically. It will actually bring about different brain states through thinking. This seems to me highly significant because in his book Rosenberg says that if you find all of this depressing (that there is no self, there is no identity over time, there is no intentionality, there is no free will) he says, well, there's always Prozac. He's serious! I mean, what else would a materialist say? He says take drugs. If you take brain-altering drugs then you'll feel better. Just how sinister that advice is, I think, is shown by Menuge’s point that we don't always need to resort to drugs. Sometimes there are cognitive therapies whereby changing your thinking you can actually alter the brain and get better.

In all of these ways it seems to me that Menuge is right – that we ought to reject these physicalist views in favor of some sort of dualism-interactionism; that is to say, we are composites of soul and body, and the soul and the body together (in particular, the brain) work together to think.


Student: It seems interesting that the discovery of things like neuroplasticity would seem to lend more evidence to something like the soul, the causal impact of the soul, and yet you see simultaneously a pull in the direction of physicalism.

Dr. Craig: Yes, though, as I say, physicalism is not as popular as it used to be. The point of Coons and Bealer is that a good many thinkers today are challenging physicalism, and this neuroplasticity would be just one piece of the evidence.

Student: Speaking broadly about this and about the nature of man, it certainly seems that (and I'm generalizing) to define man we have to find out what separates us from the other animals or creatures or other things – this part or definition in philosophy. Where I come from is that man has a mind and a rational faculty that is the ability to reason. There's another view, what I would call the biblical view, that he was the only one inspired or God-breathed – that God breathed life into him. I don't know how that translates into our having a mind and the ability to do math or chemistry. Why is there such a concerted effort to turn that off and come up with ridiculous statements? I mean, it seems like Rosenberg went out of his way to be ridiculous and it's because he's abandoned reason. Why is that? Why have they not said that we can look at logic and reason and embrace it?

Dr. Craig: That's a great question. I think that probably dualism is typically associated with theism. A dualistic view of human beings as composed of body and soul fits much more comfortably in a theistic worldview than in a naturalistic worldview, and so that's why Rosenberg says that his book is a guide to reality from the atheist view. He wants to show what reality looks like from atheist presuppositions. If he were to change his view of the mind, he might be obliged to adopt theism, and that is something that he's probably not willing to do.

As I said the other day when someone asked me whether or not if I were an atheist I would reject dualism, and I said I don't see how I could. It seems to me that these sorts of arguments are so powerful and the alternatives are so incoherent and contrary to our experience that it would be more plausible to be an atheist and a dualist even though that is a very uncomfortable fit. I think that view is becoming more popular, as I said, but nevertheless the alliance between theism and the reality of the soul is such that admitting the reality and existence of an immaterial soul seems to open the door a crack for theism.

Student: Just anecdotally, he could be asked – does he have a watch? Rosenberg. Does he have a watch? A calendar? Is he going to an event where he's going to debate you, does he buy a plane ticket? It sounds very much like the argument that Krauss had when you debated him that had the shirt that says “two plus two equals five for very large values of two.” I was wondering if Arizona State paid him 80% if he would consider that equal.

Dr. Craig: I think what several of you are underlining is the unlivability of this naturalistic worldview. Even if you come to the belief that we have no free will, that I never think about anything, indeed that I do not exist, you can't live that way. So everyday you give the lie to your worldview. And I do think you're quite right about that. It’s really unlivable.

Student: Where does that leave them? I know you can say if you're truly an atheist and you totally embrace that, you're committed to that, you're a card-carrying atheist, and you realize that this is the materialistic viewpoint – that's part of it, I guess – and the only thing that exists is physical, where do they go with the realization of the mind? You're saying it's becoming more popular to not be a materialist, that means then they have to have an alternative of recognizing the brain or the mind and yet not lead that to the assumption of a spiritual realm that could . . .

Dr. Craig: That's sort of the compromise position of non-reductive physicalism. They want to admit there are these mental states of awareness and so forth, but they don't want to go all the way to say that there is therefore an immaterial substance or soul that has these. Then they have all of the difficulties that attend that kind of halfway house. I think it would be better, as I say, for the atheist to just give up on physicalism and become a dualist, but then that opens the crack to theism because if there can be these finite immaterial substances – mental substances, minds – connected with these bodies then why couldn’t there be an unembodied mind who is the creator and designer of the universe?

Student: So the atheist you debate basically just leave it as we don't know? I know you debate a lot of atheists; I'm just curious because they have a following that is extensive and it seems to me questions would arise that they need to have some sort of answer for.

Dr. Craig: I usually don't debate these subjects because, as I say, this isn't my area of specialization, but it did come up in the Rosenberg debate that I had at Purdue University. I faithfully represented his positions here this morning, and if you go on YouTube you can see that debate and his floundering, I think, to try to defend his naturalism as well as to offer any good critique of theism. Someone mentioned Krauss – in our dialogues in Australia, what Krauss affirmed was that there is no free will, that we're just determined to do everything by physical causes, but he said those physical causes are so complex that we have to act as though we have free will because I could never predict what you're going to do tomorrow based upon physical causes. They're too complex. As I pointed out to Krauss, that doesn't affirm that we really have free will; that's just to say we can't predict the outcome of these physical causes. But nevertheless everything really is determined. And he agrees with that.

Student: What would the materialists do with non-material things like rules of logic or mathematics that seem to exist outside of any material basis?

Dr. Craig: That's a tough one. It's very interesting that the leading naturalist and physicalist philosopher of the 20th century, Willard Quine at Harvard University, believed in the reality of abstract objects. He said that modern science and the success of our scientific theory commits us to the reality of mathematical objects and similarly things like the truth of the rules of logic and other things of that sort. Even though Quine was a naturalist, he was a Platonist and believed that there are these non-physical, transcendent, abstract objects that are essential to the truth of modern science. But how he could account for this sort of bifurcated view of reality, I don't know he never did. Certain theists like my colleague J. P. Moreland have severely criticized Platonists who want to be atheists because it's just as difficult to admit into your ontology these abstract objects which are immaterial transcendent things as it would be to admit finite immaterial substances called souls.

Student: So this is just one of those uncomfortable positions?

Dr. Craig: Yeah, another one of these uncomfortable positions.

Student: Why can’t you just be a deflationist and a nominalist about abstract objects then?

Dr. Craig: That's what I would say you should do. That's my own view – I'm an anti-realist about abstract objects. He was asking about, I think, whether or not you could have a naturalistic view of reality and yet also affirm the reality of these immaterial things like souls. I was just pointing out there's some precedents for that in these Platonists. But by no means is my suggestion that the atheist is committed to Platonism. Quite the contrary.

Student: But do you think they can be committed to things like logic, as he mentioned for example?

Dr. Craig: Yeah, I think that they could probably offer, as you say, an anti-realist view and a deflationary view of truth. I think that that's defensible.[2]


[1]           This was a paper delivered at the Evangelical Philosophical Society panel for the Society of Biblical Literature, San Francisco, CA, November, 2011.

[2]           [2]Total Running Time: 35:17 (Copyright © 2020 William Lane Craig)