In their book, Philosophical Foundations for a Christian Worldview, Dr. J.P. Moreland and Dr. William Lane Craig define materialism as “the view that the only substances that exist are material substances.” In other words, Moreland and Craig are describing materialism as the belief that the only things that exist are things comprised of physical matter. Countless modernist ascribe to this worldview by incorrectly believing matter is the only thing that exists metaphysically. Consequently, these same people also believe the immaterial and supernatural worldviews are fictitious. Due to the vibrant imagery of the supernatural found in C.S. Lewis’ writings, one may find it difficult to grasp that during a period of his upbringing, Lewis believed in the metaphysical philosophy of materialism. However, Lewis eventually—through careful reflection and the realization that there were many learned people who rejected materialism—changed his metaphysical viewpoint on reality. In fact, after his conversion to theism, Lewis articulated a powerful argument against the materialistic worldview. C.S. Lewis’ argument from rationality devastates the philosophy of materialism. The aim of this post is to examine C.S. Lewis’ thought regarding the problem of materialism by studying Lewis’ argument from rationality.
The initial premise to Lewis’ argument from rationality is this: for a proposition to be considered true, false or meaningful, then said proposition must have a rational source. Lewis argues, “if the solar system was brought about by an accidental collision, the appearance of organic life on this planet was also an accident, and the whole evolution of Man was an accident too.” Lewis contends if materialism is true, then the entire universe—and of course all of the matter within it—is merely “accidental by-products of the movement of atoms.” Lewis claims if materialism is true, then all things that exist—including thoughts and propositions—will find its foundational origins in nothing more than nonsensical atomic collisions. Clearly, there is nothing rational about random and accidental natural processes. Thus, Lewis’ first premise is seamless: if materialism is true, then propositions and thoughts cannot be considered rational, because their ontology is irrational.
The second premise of Lewis’ argument claims that no physical matter—or collection of solely material objects—can institute any kind of rational thought. To prove his point, Lewis cleverly, applies this materialistic philosophy to organic life and human thought. Lewis undoubtedly understood that materialism was synonymous with physicalism—the view that “human beings [are] completely physical.” Physicalism asserts there is no such thing as the soul or an immaterial self. Thus, it would be impossible for a person to create thoughts independent of the physical body. Given the all-inclusive philosophy of materialism and physicalism, it would also apply to all parts of the body—specifically the brain. Therefore, even if man’s thoughts are complex (and appear to be rational), on the materialistic worldview, these thoughts are nothing more than a collection of accidental molecular and atomic collisions. At this point, Lewis begins to drive the dagger of doubt into materialism.
Lewis draws on the intuition that inadvertent by-products of atomic collisions do not have the explanatory power to justify rational thinking. Lewis explains the materialist’s conundrum,
If so, then all our present thoughts are mere accidents—the accidental by-product of the movement of atoms. And this holds for the thoughts of the materialists and astronomers as well as for anyone else’s. But if their thoughts—i.e., of Materialism and Astronomy—are merely accidental by-products, why should we believe them to be true?
As mentioned earlier, materialism entails everything in the universe—including thoughts—are random and accidental processes. Here Lewis unveils the serious repercussions, which surface for holding to this worldview. The quote clarifies that if materialism is true, then “all our present thoughts are mere accidents.” Skillfully, Lewis rationalizes that this would also include the thoughts of the person who believes materialism is convincing. Here, Lewis supports the third premise of his argument: propositions made in a materialistic worldview would be mere accidental by-products and one would have no reason to believe them as true.
Let us examine Lewis’ claim for a brief moment. Consider for the sake of argument that a man’s thoughts are nothing more than physical matter, which resulted from random, and accidental means. What could we anticipate of this man’s thoughts? In principle, if the thought was material, a scientist could tell how much it weighed, where it was located or its dimensional size. However, one thing the scientist could not determine is if the man’s thoughts are true or false. Moreover, if thoughts are simply physical matter, it is no different than any other natural law. Take for example the law of gravity; scientists do not claim gravity to true of false, but simply a law that exists.
Consequently, Lewis claims that if our thoughts are purely material, it is nonsensical to claim them as either true or false. To prove his point, Lewis specifically highlights the following proposition: the philosophy of materialism is true. Even deprived of much reflection, one can begin to see the underlying problem. Namely, if materialism is true, then all thoughts and rational are neither true nor false, they are simply accidental by-products of colliding atoms. Thus, according to materialism, if thoughts are not true or false, why ought one think that the proposition the philosophy of materialism is true is actually factual? Lewis accurately explains there is “no reason for believing that one accident should be able to give [us] a correct account of all the other accidents.” In other words, for any worldview to be true, it must account for rational thinking. Problematically, materialism does not.
The idea that knowledge depends on valid reasoning is an overarching theme Lewis reflects upon. In his book Miracles, Lewis explains,
All possible knowledge, then, depends on the validity of reasoning. If the feeling of certainty which we express by words like must be and therefore and since is a real perception of how things outside our own minds really ‘must’ be, well and good. But if this certainty is merely a feeling in our own minds and not a genuine insight into the realities beyond them—if it merely represents the way our minds happen to work—then we can have no knowledge. Unless human reasoning is valid no science can be true.
If our thoughts are merely a feeling in our own brain and not an external proposition, which is either true or false; then it is impossible for anyone to have knowledge. However, for the sciences to operate, actual reasoning must take place. Brilliantly, Lewis attacks materialism by saying, “it follows that no account of the universe can be true unless that account leaves it possible for our thinking to be a real insight. Consequently, if the materialistic account of the universe is correct, then the rational thought “materialism is true” would not a real insight by its own definition. Therefore, Lewis correctly asserts that the materialist claims are, at their core, self-refuting. Thus, Lewis establishes the fourth premise to his argument: human reasoning is necessary for knowledge and cannot simply be the by-product of a purely materialistic process.
Therefore, we can summarize Lewis’ thought regarding the problem of materialism by reviewing his argument from rationality. First, for a proposition to be considered true, false or even relevant, then this proposition must have a rational foundation. Lewis demonstrated that if materialism were true, then all things that exist—including thoughts—would find its most basic origins in nothing more than nonsensical atomic collisions. Furthermore, Lewis argued physical matter alone could not constitute any kind of rational thought. Next, Lewis explained how propositions that are merely accidental by-products, have no reason to be believed as true or false. Subsequently, Lewis substantiates that human reasoning is necessary for any kind of scientific knowledge—including that which is needed to establish a materialistic philosophy—and thus materialism is essentially self-refuting. Hence, the conclusion of Lewis’ argument must follow that since rationality exists, materialism is false. By examining Lewis thoughts on materialism—specifically his argument from rationality—this post has demonstrated that Lewis was correct in determining that materialism is false.
Lewis explains in his autobiography the paramount reason he was a materialist was not based on scientific inquiry or after years of study but actually due to a dire need for independence. Lewis understood that in order to keep his atheistic worldview, he must hold onto materialism. For atheism, materialism is the only game in town. Lewis did not want God looking over his shoulder and causing “interference.” However, as soon as Lewis started honestly reflecting on the workings of materialistic philosophy, he realized it did not match what he knew to be true of reality. Yet, Lewis ultimately was not committed to being comfortable, for he “didn’t go to religion to make [him] happy,” but rather to follow what was true.
 William Lane Craig and J.P. Moreland, Philosophical Foundations for a Christian Worldview (Downers Grove: InterVarsity Press, 2003), 229.
 C.S. Lewis, Surprised by Joy: The Shape of My Early Life (Orlando: Houghton Mifflin Harcourt Publishing Company, 1955), 165-181.
 Ibid., 175.
 C.S. Lewis, God in the Dock: Essays on Theology and Ethics (Grand Rapids: Wm. B. Eerdmans Publishing Co., 1970), 52.
 Lewis, God in the Dock, 52.
 Craig and Moreland, Philosophical Foundations for a Christian Worldview, 229.
 Lewis, God in the Dock, 52.
 Lewis, God in the Dock, 52.
 Lewis, God in the Dock, 52-53.
 C.S. Lewis, Miracles (New York: HarperCollins, 2002), 218.
 Lewis, Surprised by Joy, 172.
 Lewis, God in the Dock, 58.