We want to believe in equality, human dignity, value and worth, and the possibility of human flourishing and the common good. But these ideas make sense only if we have a shared human nature that makes us all the same and equally valuable. This shared human nature is not part of our physical dimension (our physical “substance”), but is part of our immaterial dimension (our immaterial “substance”). Therefore, Substance Dualism is the only way to ground and defend these ideas.
Since so much is at stake in our view of what it is to be human, are there any good reasons to believe we may be made up of a duality of body and soul? I think there are. I’ll offer three reasons this week, and another three next week.
Reason #1: Scripture Assumes we are a Body and a Soul
For believers who look to God’s Word for guidance, Scripture clearly assumes we have a body throughout, in such passages as I Cor. 12:12. This is also affirmed in God himself becoming incarnate (literally “in flesh”). Finally, believers look forward to the final resurrection where we will receive a new body (2 Cor. 5:1-5).
Scripture also clearly assumes we have a soul. God creates us in His image (Genesis 1:26-27). We know God is immaterial, so His image “in” us must also be immaterial. Furthermore, Jesus warns in Matt. 10:28 to “not fear those who kill the body but are unable to kill the soul; but rather fear him who is able to destroy both soul and body in hell.”
Therefore, believers who have a high view of Scripture have one very good reason to embrace Substance Dualism—Scripture clearly teaches that we are composed of body and soul.
It has become popular as of late for some Christian scholars (at some Christian colleges and evangelical seminaries) to deny Substance Dualism. Some try to make a form of property dualism ("Non-Reductive Physicalism") consistent with Scripture. In post 4 of this series I’ll discuss this view more and why it fails. Others go so far as trying to make Physicalism consistent with Scripture, maintaining we are essential material beings with no immaterial/spirit/soul at all! For an excellent treatment of these arguments and responses see John Cooper’s Body, Soul & Life Everlasting: Biblical Anthropology and the Monism-Dualism Debate.
Reason #2: That We Are More Than Our Bodies is Self-Evident
We just know we are more than our bodies, and so the burden of proof is on the one who wants to deny this. Even our ways of talking indicates this—we refer to our physical dimension as “our” bodies, indicating two things: (1) a soul, which has (2) a body. We just know intuitively that we are not identical to our bodies, but rather we are a soul that has a body.
David Hume, one of the leading skeptics and Physicalists of the “Enlightenment,” betrays this as he argues we have no soul. He says that when he pokes around in his consciousness and examines all his experiences he never finds an “I” (a self, a soul). But then what does he even mean by saying it is “his” consciousness and “his” experiences”? And how does he know whose experiences to “poke around in” in the first place? It is simply impossible to consistently deny we have a soul. Our language itself betrays that, even when trying to argue against the soul’s existence!
If the skeptic wants to abandon the notion of a soul, and thus of Substance Dualism, she must offer a view that is equally plausible. Furthermore, she must do so without any reference to herself as a self that is making that argument—it can’t be “her” argument! (I’ll develop this more next week.)
Reason #3: Mental Events Can’t Be Reduced to Brain Events
There are a number of human abilities that only make sense if we possess an immaterial dimension. These abilities cannot be reduced to material functions (functions of the brain).
First is “intentionality.” Notice that when we think we always think about something. We are thinking about the game last night or about the date I have tomorrow. It makes perfect sense to speak in this way, and everyone understands what we mean. A central property of our minds is this property of intentionality.
However, it doesn’t make any sense to say a purely physical thing is thinking about something. We don’t say rocks think about the game last night or that a magnetic field is thinking about what will happen tomorrow. This is simply not a property that physical things have! Since the brain is a material thing, it is equally odd to say the brain is thinking “of” or “about” something. It does not have the property of intentionality.
Therefore, since the mind has a property the brain does not have, it follows that the mind and brain are different things—that the mind cannot be reduced to the brain. In other words, it shows we have both immaterial and material dimensions—that we are two substances.
“But wait, there’s more!” A second property of the mind that is not reducible to the brain is the ability for those thoughts to be rational. I won’t say more about this here, as I’ve offered this argument against Materialism/Physicalism here. There I also show how other mental properties such as emotions, desires and choices cannot be reduced to brain events. Therefore the mind (soul) is distinct from, and cannot be reduced to the body (brain).
Unfortunately the assumption of Physicalism has pervaded our culture, and so it has become commonplace to speak as if the brain has these mental properties and capabilities. When someone is intelligent we say, “She’s got brains.” We speak of “neural pathways” as if that is all there is to having a thought. We say a memory, an emotion, or a desire exists in a certain region of the brain. Even Christian thinkers are tempted to speak in these ways, often without realizing the implications of such reductionism. There are two logical errors underlying this reductionism.
The first error is not understanding the nature of identity, and therefore not realizing the logical fallacy of saying mental events are identical to (the same as, nothing but, reducible to) brain events. It is important to understand the law of logic known as Leibniz’ Law of the Indiscernibility of Identicals. This law holds that if two things are identical, they will share all their properties in common. If Stan Wallace is identical to the writer of this blog, both will necessarily have all properties in common. If you can show they share all properties, you will prove they are (necessarily) identical. Conversely, if you can show that Stan Wallace is 6’ 5” tall, but the writer of this blog is 5’ 11” tall, you will show (necessarily) that Stan Wallace and the writer of this blog are different people, because they differ in at least one property.
So this law helps to prove two things are necessarily identical (when they share all properties in common), as well as prove two things are necessarily different (if one has one or more properties the other doesn’t have). Showing the mind has even one property that the brain doesn’t have proves the mind and brain are necessarily different things. Understanding this law of logic shows the fallacy of reducing the mind to the brain.
The second error, related to the first, is confusing constant conjunction with identity. A Substance Dualist is quick to note that the mind uses the brain to accomplish certain activities. Yet this is not the same thing as the mind being the same as the brain.
This is akin to the way I (my self, soul or mind) use my hands to type these words. Note that it is not my hands that are responsible for the text, but my thoughts (mental events). Yet my hands have to be involved to get it typed—my mind must use my hands as instruments to accomplish the activity of writing this blog. As a result, the two always come together when I want to blog—a thought exists, and hands are used to get it typed. But just because the two always come together doesn’t mean they are identical—the thought is not the same thing as my hand typing. No, my hands are the tools my mind uses.
In the same way, though the mind uses the brain to accomplish certain tasks (such as storing a memory or processing a calculus equation), it is the mind that is doing the “heavy lifting,” and using the brain as needed. Yet because they always come together (the mental event and brain event in the act of thinking), some are tempted to say this constant conjunction is the same as identity. It is not (see discussion on the nature of identity above).
Next week I’ll offer three more reasons to believe we are a soul and body—three more reasons to be a Substance Dualist. Until then, grace and peace.
For further reading I suggest Philosophical Foundations For A Christian Worldview by J.P. Moreland and William Lane Craig; Chapter 11: “The Mind-Body Problem”