C.S. Lewis' "Argument From Reason"


C.S. Lewis. Credit: Wikipedia
C.S. Lewis is renowned among Christians in the United States and abroad for being a poetic and beautiful writer of prose and fiction while at the same time exploring and defending the Christian faith. He is a well-known apologist and fiction writer, the author of the Chronicles of Narnia series in addition to other works such as The Screwtape Letters and Mere Christianity. One of his crowning achievements in the eyes of many Christians is the "argument from reason" that he published in defense of his Christian faith, which he arrived at late in life, and we're going to debunk that argument today.



The argument from reason goes like this (grabbed from Wikipedia, since I have better things to do than find the original publication of this argument):


  1. No belief is rationally inferred if it can be fully explained in terms of nonrational causes.
  2. If naturalism is true, then all beliefs can be fully explained in terms of nonrational causes.
  3. Therefore, if naturalism is true, then no belief is rationally inferred (from 1 and 2).
  4. We have good reason to accept naturalism only if it can be rationally inferred from good evidence.
  5. Therefore, there is not, and cannot be, good reason to accept naturalism.
What Lewis tried to do is wrap "naturalism" in contradiction - not atheism itself, but the philosophy of naturalism, which is the idea that everything that we observe has a natural cause, rather than supernatural, and which rejects the idea of supernatural agents (it is nowadays considered synonymous with physicalism or materialism - a definition which I adhere to.)

Naturalism is not synonymous with "atheism" - so it is important to realize that Lewis was not trying to prove that atheists are contradictory in themselves. Let's look at the propositions we are handed by Lewis one by one.

The first proposition,

  1. No belief is rationally inferred if it can be fully explained in terms of nonrational causes,
is an attempt by Lewis to essentially state that if your thoughts are all determined by physical causes (i.e. brain chemistry, neurons in your brain going off, etc.), and these things are "nonrational," then no thoughts you have are rational. "Nonrational" is a term meaning something that is not based on reason. It is different from "irrational," which is something which contradicts reason and rational thinking. Nonrational things include things such as my scone - my scone is neither rational or irrational, it simply exists. Neurons and brain chemistry are nonrational things, and Lewis thinks this means that no thoughts we have in a naturalistic world could therefore be considered rational.

There are multiple mistakes just in the first proposition. Just because something is nonrational, such as the cause of something (like my brain chemistry determining my state of mind), does not mean that the outcome is nonrational (such as if I made an argument based on logic, because of my brain chemistry). "Rational" is a word that indicates something is based on logic and sound reasoning, which can be demonstrated in an argument. The cause of the argument is not considered in the definition of "rational." A similar sentence, to demonstrate the error on Lewis' part, would be "your idea of red is determined by brain chemistry - so you can't say anything is red, because your idea of red is just chemical interactions in your head." It's a non-sequitor and it's begging the question. Why can't I call it red, just because my brain is based on chemistry? The fact that your brain is based on the laws of chemistry and physics has nothing to do with the nature of abstract ideas you create.

The second flaw is that there is now something known to philosophers and cognitive scientists called "emergence." Lewis commits what is known as the "fallacy of division," where he assumes that the whole must obey the same laws as the parts, which is untrue. Emergence is the idea that properties which exist in large systems or organisms do not exist in smaller systems or organisms, or single cells, etc. For example, one molecule of water does not feel wet - what about two? What about 50 molecules of water? When do you have enough water to call it "wet"? The property of "wetness" is emergent in water, just like consciousness and ideas are emergent in human beings. The more brainpower you amass, in certain configurations with certain chemicals interacting with the brain, and you get unexpected, emergent results, which are not based on any single part of the brain but rather the entire brain as a whole. You can indeed get rational thinking from nonrational parts, and the proof of this is that you can think rationally at all.

To expound more on emergence, think of salt. Chemically, table salt is sodium and chlorine atoms, and together they can make the molecule sodium chloride - which is table salt. We perceive the taste of salt, and call it "saltiness", but the constituent parts, sodium and chlorine, do not taste salty - salty taste is an emergent property of sodium chloride, where the whole exhibits properties that the parts do not, and which you cannot predict based solely on examining the parts individually.

In essence, emergence is "the whole is greater than the sum of it's parts."

That last sentence leads us to the final flaw with this proposition - Lewis is trying to take the idea of naturalism, which rejects the proposition of supernatural forces or entities (typically because there's no evidence of them), and say "but you can't think rationally without supernatural forces." This is redefining the question of how humans can think or know anything, and phrasing it so that it requires a supernatural world to function, and then asking the naturalist to explain how it could happen without supernatural forces. That's fine in a thought experiment, but as a supposedly logical argument, you cannot simply say "my magic wish-thinking explains it, but I don't understand how you can think rationally if you're just made up of chemicals, so you must be wrong," which is essentially what he's doing. His first proposition already presupposes the necessity of a supernatural world for us to think rationally - maybe if he could demonstrate this to be true, this proposition wouldn't be so ludicrous.

Moving onto the second proposition, 

  • If naturalism is true, then all beliefs can be fully explained in terms of nonrational causes,
Lewis is committing more fallacies. His first four words are already showing intellectual dishonesty - "if naturalism is true" is saying, essentially, "if supernatural things - such as my god - don't exist." He is again presupposing that his god does exist, and acting as though there's a problem for people who reject this, rather than proposing evidence first that his deity exists, and then postulating how this deity explains other problems.

The second part of this proposition is relatively benign. All things a human can think seem to be caused by the brain itself, so the second part is pretty much correct.

Thirdly we have
  • Therefore, if naturalism is true, then no belief is rationally inferred (from 1 and 2),
This is patently untrue, because he has not demonstrated the first proposition to be true. The first proposition, as we discussed, supposes that if we are based on brain chemistry, we are not able to form rational thoughts, when in fact there's no reason to think this. As previously mentioned, this is Lewis admitting that he already thinks of the human mind as requiring something supernatural, and then rejects the natural claim and says "that isn't possible," without demonstrating that anything supernatural is required - much less demonstrating that rational thinking is somehow impossible if there isn't something supernatural. This is all just conjecture.

Fourth proposition:

  • We have good reason to accept naturalism only if it can be rationally inferred from good evidence.
Wrong. This is the culmination of everything wrong with this argument. This proposition explains the complete mindset of Lewis and how he even arrived at his first flawed proposition in the first place. We don't have "good reason" to accept naturalism only if it can be "rationally inferred" from "good evidence" - this is like saying we should accept supernatural claims on principle without evidence, for no reason, and the burden of proof lies on people that don't do this. This is horrendously erroneous. You don't start with "I believe in supernatural stuff" and then go to "you have to prove that supernatural stuff isn't possible" or "prove that only natural stuff exists," you idiot! You are the person who made a claim that "supernatural" forces and entities exist, so the burden of proof lies on you. I don't have to justify anything to make naturalism valid. It's the default position. We can demonstrate natural things exist, we can't demonstrate that supernatural things exist.

All of the propositions are flawed and essentially just say "reality doesn't make sense without supernatural stuff, therefore you're wrong and supernatural stuff exists," without actually pointing to empirical data that agrees with the ideas. Lewis tries to spin the argument into a circle requiring those who reject supernaturalism to prove their position, rather than the other way around, and then pronounces victory like a toddler who says to his older brother, "I have an invisible forcefield! You can't hurt me!"

In short, this argument is nonsense of the highest degree, and should be scrapped along with the deity he professed to believe.

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