After reading the book, my friend shared his reactions via email. Overall, he was impressed by Wilson's argumentation and felt he did a very good job of substantively addressing important issues in relatively little space. My friend did, however, take issue with how Wilson, via Evangelist, addressed an atheist named Mark. My friend said:
With Mark, for the Evangelist to argue that reason, being a product of random forces, cannot be trusted, nor said to produce a "true" or "false" result is, while technically correct, not a very persuasive argument. It's possible that the chemical reactions resulting from random processes that Mark calls reason are really just random processes, but in the end, it doesn't matter in terms of whether the atheist should believe in God.
Since I devoted some time to responding to my friend's criticism, I thought I'd make my effort serve double duty by posting an edited excerpt of my reply below:
The argument from rationality for the existence of God is one that popularized in his book Miracles and that contemporary Christian philosophers such as Alvin Plantinga and Victor Reppert (author of C. S. Lewis's Dangerous Idea: In Defense of the Argument from Reason and owner of a blog devoted to discussion of the argument) have advanced.
One has to keep in mind that the dispute between the atheist and the theist doesn't consist merely of disagreement about particular facts but is in actuality a clash of worldviews, systems of interpretation that rest on certain presuppositions about the nature of reality, the sources and scope of human knowledge, and ethics. All of these are intertwined and interrelated. What one believes in one area has consequences for another. For example, if I assume that reality consists exclusively of matter and material processes, a necessary consequent is that there are no such things as objectively existing moral truths. Likewise, claims to knowledge of moral absolutes would be inconsistent with the belief in such a universe. What the argument from reason asks is, given our belief that we are able to form true beliefs that correspond to the world outside our minds and that we are able to make reliable inferences and deductions, what kind of universe best accounts for or grounds these phenomena.
In Miracles, Lewis contrasts the naturalist and the supernaturalist. The former, he says, contends that reality is a closed system in which every state of affairs can be explained (at least in principle) in terms of some prior state of natural affairs. He writes (quotations are from the 1978, Collier Books paperback edition):
Lewis maintains that all that is necessary in order to demonstrate that naturalism is false is to identify something that operates independently of the system.
He then sets out to demonstrate how reason fits the bill as one phenomenon that cannot be accounted for in completely naturalistic terms and is therefore evidence that nature is not all that exists.
Lewis starts by stating that the possibility of knowledge and science depends on the validity of reasoning. When we use words like "therefore," "must be" and "since" with respect to beliefs of which we are certain, we are only correct to the extent that our beliefs actually correspond to what is the case outside our minds. "But if this certainty is merely a feeling in our own minds and not a genuine insight into realities beyond them -- if it merely represents the way our minds happen to work -- then we can have no knowledge" (14). He quotes J. B. S. Haldane: "If my mental processes are determined wholly by the motions of atoms in my brain, I have no reason to suppose that my beliefs are true...and hence I have no reason for supposing my brain to be composed of atoms" (15).
Lewis proceeds by stating that in a sentence such as "Grandfather is ill today because he ate lobster yesterday," the word "because" indicates a cause and effect relation. Eating the lobster had the effect of Grandfather being ill. In a sentence such as "Grandfather must be ill today because he hasn't got up yet" (and we know that he has characteristically been an early riser), "because" does not indicate cause and effect (not rising early isn't what caused Grandpa's sickness). Rather, "because" here indicates the reason for our belief that Grandpa isn't feeling well.
Lewis notes that this relation is what logicians call Ground and Consequent. According to a purely naturalistic or materialistic (in the philosophical sense) scheme, all our beliefs are simply physical events that are the effects of prior physical (and non-rational) causes. And, as Lewis points out, "a train of thought loses all rational credentials as soon as it can be shown to be wholly the result of non-rational causes" (26).
The argument from reason sets before us two sets of presuppositions and asks which set provides the necessary preconditions for what we all take for granted, namely the validity of reason and our ability to form true beliefs about the extra-mental world. On one hand there is the belief that mind and rationality emerged from non-rational material processes in which case our beliefs are not the results of processes of reasoning but are thrust upon us by our biology. On the other hand is the theistic presupposition that rationality has always existed and is ultimately behind life. The atheist rejects belief in the existence of God in the name of rationality and science. However, he or she holds to a worldview in terms of which rationality, logic, and knowledge are unintelligible. In his review of atheist Richard Dawkins's book The God Delusion, noted Christian philosopher Alvin Plantinga offers a condensed version of the argument: