The Single Best Argument Against Philosophical Materialism?
by R.P. Ritchie
Filed under Atheism
A Dilemma for Materialists
In my experience, it's often difficult for my intelligent atheist friends to seriously consider arguments for the truth of Christianity. An argument from the resurrection of Jesus remains implausible because their worldview fundamentally excludes this sort of event. In light of this, I'd like to engage one popular form of this worldview, namely philosophical materialism.
Thus here’s my dilemma for materialists:
1. Either subjective experience, in its capacity as subjective experience, is relevant in the explanation of behavior or it is not.
2. If subjective experience is relevant in the explanation of behavior, then materialism is absurd (more than that, it is unambiguously false).
3. If subjective experience is not relevant in the explanation of behavior, then materialism is absurd.
4. Therefore, materialism is absurd.
The conclusion necessarily follows from those three premises, if all are true, so let's examine each premise one at a time.
Premise (1): A Philosophical Axiom
Premise (1) is obvious and uncontroversial. It appeals, in philosophical jargon, to the “law of the excluded middle”, which holds that for any assertion X, either X is true or not-X is true. One example of this axiom is that either Barack Obama is a horse or he is not a horse. There can be no “middle” position wherein he is somehow neither of those two possibilities. Premise (1) is simply another example of the same axiom where “subjective experience, in its capacity as subjective experience is relevant in the explanation of behavior” is used instead of “X” or “Barack Obama is a horse”.
Premise (2): A Definitional Point
“Materialism” is a term used somewhat inconsistently by philosophers. However, materialists of every stripe are at least committed to the “causal closure of the physical domain.” For this reason, the truth of materialism and the explanatory relevance of subjective experience are mutually exclusive.
Perhaps most commonly, “materialism” is used interchangeably with “physicalism” as the view that everything including people consist of nothing by physical matter and that a person’s mental states just are (or at least are reducible to) physical states of their brains. But I am using the term in a broader sense to encompass the position known as “dual aspect theory” (or sometimes “property dualism” or “non-reductive materialism”) as well.
Dual aspect theorists are willing to admit that mental states are something distinct from physical states and that they are not reducible to physical states. This means, as the dual aspect theorist David Chalmers has put it, that our mental states are such that they could not be explained by anything we could reasonably apply the term “physics” to. Rather, on this theory there are as-of-yet undiscovered “psychophysical laws, specifying how [mental states] depend on physical properties.”
Importantly, however, both physicalism and dual aspect theory (and any other theory that could reasonably come under the term “materialism”) is committed to what may be called “The Causal Closure Thesis." This thesis holds that there are no non-physical causes that operate on the physical level. This does not rule out the possibility—important to some theories of quantum mechanics—that some physical events are uncaused and random. But it does mean that even though the dual aspect theorist admits that non-physical mental states exist, he denies that they have any effect on the physical domain.
As Chalmers puts it, “the physical domain remains autonomous,” and “the view makes experience explanatorily irrelevant.” Rather, the true explanation of behavior may be diagrammed as follows:
The sole explanation of the behavior in question (reaching for an apple) is the antecedent physical cause of that behavior. There may be an arrow from a physical state of affairs to the mental state of desiring an apple, but there could never be an arrow from that or any other mental state to a physical result. Stephen Hawking is a materialist and demonstrates his commitment to this position in his recent book The Grand Design:
“Recent experiments in neuroscience support the view that it is our physical brain, following the known laws of science, that determines our actions, and not some agency that exists outside those laws...It is hard to imagine how free will can operate if our behaviour is determined by physical law, so it seems that we are no more than biological machines and that free will is just an illusion.”
Therefore, if materialism is true, then subjective experience, as Chalmers has put it, is “explanatorily irrelevant”; Premise (2), in other words, is sound.
Premise (3): Why Materialists Can’t Employ an Evolutionary Theory of Knowledge
It is tempting to jump to an overly simple objection to the materialist position at this point. Physics is governed by physical laws, not reason. As Victor Reppert has put it, when there is an avalanche the rocks do not move as they do because they think it would be a good idea to do so, but because they “blindly” obey non-rational physical laws. Why should we expect the atoms in our brain to behave any differently? Shouldn’t they too blindly follow non-rational physical laws? And, if so, why should we expect the result of such non-rational behavior would be rational and trustworthy? And, of course, the materialist must, to avoid absurdity, think his mental states are rational and trustworthy or else he could have no reason for believing materialism to be true in the first place.
C.S. Lewis used this as the basis for an argument for the existence of God in his book The Case for Christianity:
"Supposing there was no intelligence behind the universe, no creative mind. In that case, nobody designed my brain for the purpose of thinking. It is merely that when the atoms inside my skull happen, for physical or chemical reasons, to arrange themselves in a certain way, this gives me, as a by-product, the sensation I call thought. But, if so, how can I trust my own thinking to be true? It's like upsetting a milk jug and hoping that the way it splashes itself will give you a map of London. But if I can't trust my own thinking, of course I can't trust the arguments leading to Atheism, and therefore have no reason to be an Atheist, or anything else. Unless I believe in God, I cannot believe in thought: so I can never use thought to disbelieve in God."
But haven’t we made that dangerous inference Richard Dawkins is always warning us about from the appearance of design to the existence of design? And, in this case, like so many others, shouldn’t we look to Darwinism to set us straight? William Hasker provides a nice summary of the position:
“The central idea of Darwinist epistemology; is simply that an organism’s conscious states confer a benefit in the struggle to survive and reproduce. Such responses as discomfort in the presence of a chemical irritant, or the awareness of light or warmth or food, enhance the organism’s ability to respond in optimal fashion. For more complex animals there is the awareness of the presence of predator or of prey, and the ability to devise simple strategies so as to increase the chances of successful predation or of escape therefrom. As the organisms and their brains become more complex, we see the emergence of systems of beliefs and of strategies for acquiring beliefs, and the strategies that lead to the acquisition of true rather than false beliefs confer an adaptive advantage. Natural selection guarantees a high level of fitness, including cognitive fitness.”
But though this Darwinist sort of reasoning is quite convincing as an explanation of the apparent design of certain physical attributes of living things (such as the warm coat of arctic animals or the beaks of finches) it is unconvincing as an explanation of the reliability and rationality of mental states under a materialist worldview. This is because on such a worldview, as I noted above, subjective experience is utterly irrelevant as an explanation of one’s behavior. If this is true, then there is no survival advantage to proper thinking, meaning that evolution would be powerless to naturally select for proper thinking.
For example, if one person reacted to a vile of poison with the thought that poison is healthy and delicious and the physical state of running from the poison his thinking would be naturally selected over a person who reacted to the vile by thinking poison is poisonous and proceeded to take a sip. As Hasker puts it, on materialism “conscious experience is invisible to the forces of natural selection.” Or, in Chalmers’ colorful words “[t]he process of natural selection cannot distinguish between me and my zombie twin.”
In light of this, we can see that if subjective experience is not relevant in the explanation of behavior, then we have no reason for believing our thoughts to be true and, therefore, no reason for believing that subjective experience is not relevant in the explanation of behavior. Any position we might take under such conditions would be absurd, so Premise (3) is also sound.
A Religious Conclusion
Now we've reached the unavoidable conclusion that materialism is absurd. But so what? Thomas Nagel notes that we shouldn’t jump to the conclusion that Christianity or even theism is true from such an argument. He calls the “overuse of evolutionary biology to explain everything about life, including everything about the human mind...ludicrous.” And he admits that “the capacity of the universe to generate organisms with minds capable of understanding the universe… has a quasi-religious ‘ring’ to it.” But he concludes that “I think one can admit such an enrichment of the fundamental elements of the natural order without going over to anything that should count literally as religious belief. At no point does any of it imply the existence of a divine person.”
I think that Nagel is right about this. In fact, even C.S. Lewis provides further evidence for this position. Lewis converted from atheism in reaction to the argument above (or something very near to it). But he did not immediately convert to Christianity. Instead, he sought refuge in the philosophy of absolute idealism.
But such philosophies have problems, which is why you see so few absolute idealists today. And, in any event, once materialism is given up, the door for Christian apologetics is thrown wide open. A reassessment of the argument for the resurrection, for example, is warranted.
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