Book Review: C.S. Lewis’s Dangerous Idea: In Defense of the Argument from Reason by Victor Reppert

It was with much anticipation that I began reading Victor Reppert’s book C.S. Lewis’s Dangerous Idea: In Defense of the Argument from Reason.  Shortly after discovering the discipline of apologetics, theArgument from Reason (AFR) was one of the first arguments I remember coming across and I recall wondering, “Why don’t more apologists use this argument?” 

It was with this question, and others like it, that I began reading Reppert’s book and not only did I find the answers to a number of my questions, but it became apparent to this reviewer that the AFR is a much richer argument than I had previously imagined.  However, I want to be sure to point out that this book is not just for those interested in the AFR.  Lewis enthusiasts will also greatly benefit from it’s pages as Reppert addresses questions about Lewis’s apologetic methodology and further dispels some of the various myths that surround Lewis and his history.  These include Lewis’s supposed loss of confidence in apologetic arguments and the popular claim that philosopher Elizabeth Anscombe demonstrated Lewis’s AFR to be invalid.

In Chapter 1, the author makes a case that Lewis and his arguments should be taken seriously and while Lewis was not a professionally trained philosopher, he possessed “outstanding philosophical instincts” [p. 12]. It is Reppert’s conviction that “great thinkers are always the ones that make us think harder for ourselves, not thinkers who do our thinking for us” [p. 13] and he clearly includes C.S. Lewis among them.

Further, this reader strongly agrees with Reppert’s contention Lewis’s work has been “underutilized.”  He states:

“The way one honors Lewis’s apologetic achievement, it seems to me, is not simply by repeating what he says, but by developing his ideas, asking probing questions of them and developing the discussion in ways that reflect one’s own thinking as well as Lewis’s…I believe that despite Lewis’s enormous popularity, subsequent apologists have underutilized the resources that he has provided for them” [p. 14-15].

Indeed.  As a teacher myself, I sometimes develop lessons from ideas called “lesson seeds.”  These are brief, core ideas that one must take an develop into a lesson of their own.  In the same way, while Lewis’s arguments are sometimes presented as the final answer, it would seem that many times, according to Reppert, Lewis’s arguments would be better served if treated as “apologist seeds.”  Core ideas that the apologist can take, develop and make their own.

In Chapter 2, Reppert addresses the question, “What constitutes a successful apologetic argument?”  Further, he assesses whether or not it is best to view Lewis’s argument from the perspective of fideism, strong rationalism, or critical rationalism.

In Chapter 3, the author points out [and this reader would tend to agree] that “one phenomenon that is sometimes neglected in the development of theistic arguments is the existence of rational thought.  Does our very thinking provide evidence that theism is true” [p. 45]? 

After briefly surveying other thinkers who have used some form of the AFR, Reppert begins to formulate the AFR as presented by Lewis and addresses the criticisms raised by philosopher Anscombe and other scholars.

In Chapter 4, this reviewer was surprised to learn that, as Reppert explains, “…the argument from reason is indeed not one argument but several” [p. 72].  The author proceeds to lay out each of the arguments in their logical forms and then briefly expounds on each one.  They are as follows:

  • The Argument from Intentionality
  • The Argument from Truth
  • The Argument from Mental Causation
  • The Argument from the Psychological Relevance of Logical Laws
  • The Argument from the Unity of Consciousness in Rational Inference
  • The Argument from the Reliability of Our Rational Faculties
In Chapter 5, Reppert builds on the several arguments presented in the previous chapter and contends that when one analyzes these arguments, “these phenomena require explanatory dualism” [p. 85].  The author’s main contention here is that “some events in nature can be explained in terms of purely mechanistic causes, the elements of rational inference…cannot” [p. 87].  Reppert thoroughly explores whether or not our reasoning capabilities, that both the naturalist and the theist have to assume are reliable to conclude anything, fit better in an atheistic universe or a theistic one.

Readers will especially enjoy Reppert’s treatment of the commonly proposed Darwinian explanation that evolution would select for rationality as opposed to irrationality.

Reppert concludes:

“…the force of the arguments from reason is to show that the fundamental fact of the universe must be rational.  Theism is a worldview that fits this requirement, though I have not attempted to show that it is the only one that does.  Naturalism, theism’s chief rival for the mind of the West, does not” [p. 104].

Finally, in Chapter 6, Reppert deals with what he has coined “the inadequacy objection.”  As the author explains, this is when one claims that to invoke souls or God as an explanation is to explain little to nothing at all.

For example, Reppert deals with the claim by prominent “new atheist” Daniel Dennett that by invoking God to explain rationality, one is guilty of question begging.

Reppert retorts:

“Explaining reason in terms of the inherent rationality of God is no more question-begging than explaining physical states in terms of prior physical states.  If the foregoing argument is correct, then explaining reason in terms of unreason explains away and undercuts the very reason on which the explanation is supposed to be based” [p. 122].

This reader also enjoyed the author’s treatment of Scientific Fideism.  Here, Reppert proves to very fair minded toward both the theist and the naturalist and is candid about the fact that various factors contribute to how one chooses which worldview is true.

Further, Reppert proves to be very restrained regarding his own conclusions and successfully models what I would call a “humble apologetic:”

“…I am not going to defend the claim that the arguments from reason close the case against naturalism.  Nor do I seek to sow that any naturalist who pays attention to these arguments can remain a naturalist only at the cost of patent irrationality.  Single arguments are rarely sufficient to bring about a worldview change in reasonable people.

However, I contend that the arguments from reason do provide some substantial reasons for preferring theism to naturalism.  The “problem of reason” is a huge problem for naturalism, as serious or, I would say, more serious, than the problem of evil is for theists.  But while theists have expended considerable effort in confronting the problem of evil, the problem of reason has not as yet been acknowledged as a serious problem for naturalism” [p. 128].


Although C.S. Lewis’s Dangerous Idea only weighs in a meager 132 pages, it is packed full of great insights.  Honestly, this reader was pleasantly surprised at how much I learned from Reppert.  While I ordered the book expecting to learn much about C.S. Lewis’s AFR, there was so much more to gleam from it’s pages.

Reppert’s book is one of the most fair minded I have read.  Absent are the many times bombastic claims of both the theist and the atheist.  The author gives both sides of the debate a fair hearing and represents them honorably.  Further, he allows the arguments to speak for themselves and doesn’t attempt to stretch the conclusion of his arguments.  Sometimes I wished he would have!  This reader found Reppert’s conclusions sound, but humble.

This work has given me a new appreciation for the AFR and the breadth and depth the argument actually covers.  Victor Reppert has written a fine book that I highly recommend and for those who want to understand the history, development and progress of the AFR should place it at the top of their reading list.  However, naturalists beware.  The AFR, made popular by C.S. Lewis, is a more dangerous idea than this reader previously imagined and in C.S. Lewis’s Dangerous IdeaVictor Reppert demonstrates why.

Apologetics 315 Book Reviewer Chad Gross is a graduate of Frostburg State University (BS) and has a Master’s Equivalency in education.  He currently is working toward an Apologetics Certificate through Biola University.  He is the founder and director of Truthbomb Apologetics. Chad teaches elementary school while leading Christian Apologetics classes at Faith Christian Fellowship in Williamsport, MD. Chad and his wife, Danielle, live in Hagerstown, MD with their two daughters, Emma and Lily Opal.

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Brian Auten is the founder emeritus of Apologetics315. He is also director of Reasonable Faith Belfast. Brian holds a Masters degree in Christian Apologetics and has interviewed over 150 Christian apologists. His background is in missions, media direction, graphic design, and administration. Brian started Apologetics315 in 2007 to be an apologetics hub to equip Christians to defend the faith.

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