Substance Dualism Is Not the Only Option for Christians

Unfortunately, most Christians are taught, or somehow assume, that substance dualism is true. Often, substance dualism is the view that humans have two separate, distinct, and complete entities: the soul and the body. Historically there have been other positions, but oftentimes this position is either taken for granted or taught as if it’s the only position available to the Christian. Take this passage of an article from a professional, peer-reviewed article:

“The proposition that we as humans have, in addition to our physical bodies, a non-material component is referred to in philosophical circles as substance dualism. It is also known as Cartesian dualism . . .” —John R. Baumgardner and Jeremy D. Lyon, “A Linguistic Argument for God’s Existence,” in Journal of the Evangelical Theological Society vol 58, no. 4 (December 2015): 779.

This statement claims, if implicitly, that the only position (“the position”!) that allows for an immaterial aspect to a human’s existence is that of substance dualism. This is in a peer-reviewed, professional journal. Such a statement is intellectually irresponsible as there are other positions on the soul being immaterial other than substance dualism. However, this is often how this issue is dealt with, i.e., by stating that if one is a Christian he must hold to substance dualism. After all, the soul and body are different. This is certainly a very popular position. It has been around at least since Plato, and was made popular by Descartes (as the article points out). It is popular in lay-level teaching in the Church because many hold (as Plato and Gnosticism did) that the soul is the true person, and/or that matter is evil.

An Explanation of Substance Dualism

The substance dualism in question is popularly known via Descartes. He wanted to start fresh in trying to discover what can be known without any chance of doubt. Since the senses can fool us, we can’t use them. Further, we sometimes think we are awake but are really sleeping. We must start with something that in itself cannot be doubted. This indubitable starting point was that he could not doubt he was doubting. And if he were doubting, he must be thinking. If he was thinking, he must exist. Thus his famous, “I think therefore I am.”

In his quest to arrive at what can be known with certainty, he argued that the soul is a complete substance apart from the body. While he claimed that he couldn’t doubt that he was doubting, and that therefore he must exist he had to deduce the existence of God, the physical body, and the material world. But if the body required further deduction from the soul (or mind), then it must be a complete substance in itself as well. Thus, the soul/mind and body are each complete substances in themselves. Since each substance is complete, this theory is known as substance dualism.

Problems With Substance Dualism

Apart from there being no biblical support for substance dualism (this in itself does not exclude the possibility as the Bible does not explicitly teach against it), it has serious philosophical problems. The main problem was recognized by Descartes himself. If the soul/mind is a complete substance apart from the body, and it is immaterial while the body is material, then how do they relate to each other? This is known as the mind-body problem. Substance dualists have attempted to solve this problem ever since it was conceived, with no clearly satisfying answer. Physical substances have no clear relation to immaterial substances.

An Alternative: Hylomorphism

An often forgotten and ignored position is that of Aristotle: hylomorphism. This has a rich tradition in Christian teaching, especially through Thomas Aquinas. Instead of arguing that the soul and body are complete substances in themselves, hylomorphism teaches that the soul and body form a complete unity. Neither the soul nor the body are complete in themselves. The unity is the person. Without the soul the body is not a complete substance, and vice versa. In this view the soul and body work together. The soul “informs” the body and makes the body what it is. This is not a spatial filling of the body, but a metaphysical “making the body to be of a certain kind.” In Aristotle’s language the soul is the formal cause of the body.

This avoids the mind-body problem and better accounts for the biblical data since the body is resurrected. Why have a bodily resurrection if the soul is a complete unity and is the real person anyway? Further, the body is not said to be evil in contradistinction to the soul, nor is the soul ever hinted at being the real person. The person as a whole is the real person. Once we reject Descartes’ reasons for holding this theory there is no good reason for being a substance dualist.

As a Thomist I am often asked how we overcome the mind-body problem. For an Aristotelian/Thomist, there is no mind-body problem. We reject the starting points of Descartes and thus don’t have his problems. As a rationalist he rejecting external reality as a starting point and thought he had to prove it was there. As empiricists, we start with the extra-mental world as the foundation of all knowledge.

The point of all this is that substance dualism is not the only option if one wants to maintain the existence of the soul. In my opinion it is not even the best option. Hylomorphism is simpler, avoids the mind-body problem, and makes sense of the biblical data.