What is Christian Physicalism?
The dominant view in the history of Christian thought has been some version of dualism, according to which, in addition to the physical body, there is an immaterial soul. Descartes held that the soul was neither extended nor located in space, while Augustine and Kant maintained that the soul was fully present throughout the body, but present in a different way from a physical entity. And while Descartes thought that the soul was itself a substance in the sense of a thing with its own independent essence, Aquinas saw the soul as a subsistent life-giving organizing principle that informs the human body. But the consensus was that the soul could exist independently of the physical body.  This was not viewed as ideal, since God clearly intended us to be integrated wholes. Each person is created as a union of body, soul and spirit (1 Thessalonians 5: 23). Yet as a result of sin, we physically die (Romans 6: 23), and the soul is separated from the body. So that it is the same person who dies that is raised to new life, as scripture clearly teaches (Job 19: 26-27; 2 Corinthians 5: 4; Revelation 6:9-10), it was held that God in His mercy maintained the soul in existence until the resurrection.
Fairly recently, some Christian thinkers have argued that this understanding of anthropology is incompatible with a modern scientific worldview, and is not required on scriptural or sound theological grounds. For many, the increased evidence of the local dependence of mental functions on specific regions and activities in the brain is best explained by the idea that we are fundamentally physical creatures (physicalism). More specifically, it is typically claimed that while the mind is something more than the brain, still the former cannot exist without the latter.
For example, according to Lynne Baker and Kevin Corcoran, the person is “constituted” by a physical body. A typical analogy is with a statue of David and the lump of marble it is made of. The marble constitutes the statue, but if the marble were pulverized, it would continue to exist, but the statue would not. Likewise, having a body is a necessary condition for being a person, but one only qualifies as a person if one also has the capacities for first-person awareness and intentional states. So, if these capacities are lost through disease or brain damage, we may have a human body, but not a person. Thus, constitution is not identity, because persons and bodies have different “persistence conditions”: a human body may persist even though a person does not.
Alternatively, on Nancey Murphy’s view, we can say that higher mental states emerge from the brain, thereby bringing novel causal powers into the world; but still the mind is entirely dependent on the brain. The idea of emergence is typically motivated by examples. A single H2O molecule does not exhibit liquidity, but liquidity emerges when we have enough molecules at the right temperature as they are then able to move freely (unlike the frozen state) without separating (as in the case of gas). John Sperry also gave the analogy of a wheel of molecules: no individual molecule can roll by itself, but the ability to roll emerges when molecules are configured as a wheel. On Murphy’s view, the right kind of brain gives rise to higher order mental states, like conscious beliefs, desires and decisions, that act back on the brain and body. This is known as downward (mental-to-physical causation).
Christian physicalists typically argue that nothing is lost by eliminating the traditional soul. On the contrary, it is claimed that the soul is a liability, because it conflicts with the causal closure of the physical world, would violate laws of physics (especially energy conservation), and has been made redundant by the amazing advances of empirical neuroscience. It is further argued that central Christian teachings on the resurrection and incarnation can still be affirmed, and so there is no reason for Christians to fear a physicalist anthropology.
In subsequent posts, I will consider some of these arguments, starting with the claim that a modern scientific worldview has made the soul untenable, and then exploring foundational philosophical and theological issues.
For a fuller account of the history of thought about the soul, see Stewart Goetz and Charles Taliaferro, A Brief History of the Soul (Malden, MA: Wiley Blackwell, 2011).
Kevin Corcoran, Rethinking Human Nature: A Christian Materialist Alternative to the Soul (Grand Rapids, MI: Baker Academic, 2006) and Lynne Rudder Baker, Persons and Bodies: A Constitution View (Cambridge: Cambridge University Press, 2000).
Nancey Murphy, Bodies and Souls, or Spirited Bodies? (New York: Cambridge University Press, 2006).
[Angus Menuge is professor of philosophy at Concordia University Wisconsin and President of the Evangelical Philosophical Society. His research interests include philosophy of mind, philosophy of science, apologetics and C. S. Lewis. He earned his Ph.D. in philosophy from the University of Wisconsin-Madison, and a Diploma in Christian Apologetics from the International Academy of Apologetics, Evangelism and Human Rights, Strasbourg. He is editor of C. S. Lewis: Lightbearer in the Shadowlands, Christ and Culture in Dialogue (Crossway, 1997), Reading God’s World (Concordia Academic Press, 2004) and Legitimizing Human Rights (Ashgate, 2013). With Joel Heck, he is co-editor of Learning at the Foot of the Cross (Concordia University Press, 2011), and he is author of Agents Under Fire: Materialism and the Rationality of Science (Rowman and Littlefield, 2004).]