It should not be too difficult to persuade the reader that “reason” is a controversial concept. What may be a greater challenge is to agree upon a typology of different ways that the word is used, or, even if common ground can be found there, upon which of these are legitimate and illegitimate. Without further ado, I would like to propose four legitimate uses of the word and then speak of some hybrids and even fuller confusions. Let us call these:

1. reason as human faculty;

2. reason as human activity;

3. reason as a completed set, or product, of the activity;

4. reason as a transcendent principle.

There are simpler breakdowns given by eminent authorities on the subject, such as where Paul Helm divides between a “substantive” and “procedural” sense of reason.1 In other words, sometimes the word is used regarding its substance, or “what it is.” Other times it is used in terms of its procedure, or “what it does.” This is a clear and uncontroversial distinction. However, it will not quite cover all of the intricate details that mark our relevant confusions in this discussion.

Reason as a Human Faculty

First, reason refers to a human faculty. It is the nature of man to “have” reason. In exploring what this means, I will deliberately avoid what may be profound questions of mind-body interaction or cognitive science. In the interest of simplicity, let me cite one dictionary of philosophy defining reason as “1. the intellect; the capacity to abstract, comprehend, relate, reflect, notice similarities and differences, etc. 2. the ability to infer.”2 To speak of a “capacity” or “ability” is to speak of reason in terms of faculty. At its core, it is that dimension of our being which thinks. Only reason thinks. That cannot be stressed enough.

We will hear much in these matters about how such and such cannot be “by reason” or “upon reason” and so forth; and we may want to ask at that moment if the critic of reason is not attempting something analogous to improving the air quality by suppressing our breathing in favor of some other potential intake. The religious man in the modern West has been pushing back against rationalism (not to mention empiricism) so much that he had long ago begun to assume the modernist’s definition of reason. He has in his mind such targets as “autonomy” or “speculation” or “skepticism,” and has learned from his interlocutor to call these things by the name “reason.” He then begins to banish from various dimensions of Christian life and thought precisely thought. 

At certain points in the course of our study, the reader will observe statements in which this occurs. They are not rare. A whole cluster of fallacies may be at work, but always a straw man at the heart of it. The relationship between reason and nature when it comes to truths consequential to God’s existence and attributes is imagined as the proverbial “ladder of reason” up to God, carefully sidestepping anything that Scripture may have to say about things. However, when it comes to reason’s role, we are speaking much more modestly about the ordinary mode of thought, as another author put it, “the capacity to self-consciously understand and to apply.”3 Such is the same capacity as when a preacher constructs his sermon or when his hearers attempt to understand what they are hearing. 

Now we cannot speak of an “ability” or “capacity” without meaning something like a substance; yet this substance is not like a static material specimen. One question we will want to ask is whether or not the reception of God’s truth by this faculty ought to ever be pit against the reflective activity of this faculty that we also call “reason.” The idea of the sensus divinitatis is crucial to this aspect of reason. For Calvin this implied an internal “sense” or “idea” of God, though he adds “the memory of which he constantly renews and occasionally enlarges.”4 Turretin said,

“The mind of man is a tabula rasa not absolutely, but relatively as to discursion and dianoetical knowledge (which is acquired necessarily by inferring one thing from another); but not as to apprehensive and intuitive knowledge.”5

Thus reason is first of all a “thing” that man has in himself, or as an essential quality of his being. 

Reason as a Human Activity

Second, reason refers to a human activity. Here is where we use the word “reasoning” to more clearly mark out the verbal sense. The aforementioned procedural reason (as distinguished from substantive reason) performs three functions according to Helm: 1. to show necessary connections in logic; 2. to show errors in our reasoning; and 3. to show relationships between otherwise seemingly unrelated truths.6 Reason clarifies truths already believed and demonstrates in order that such truths can be believed with greater certainty, or in some cases, seen to be true for the first time. 

Sometimes the word “judgment” is used to signify either a proposition or a demonstration; yet even of the latter there is a very informal sense. When we say that someone “sees” something to be the case, that person has made a judgment of the mind. The idea certainly need not mean that one’s reason is elevating itself above other human reasoners, much less above the truth of God. The judgment of the mind is nothing more than the insight that something is the case on the logical ground of something else being the case. It is a recognition of the logic of the facts. This kind of judgment is not like a ruler or calculator, but rather like the eye that looks out toward the ruler or calculator.

While Scripture is filled with warnings against the more self-reliant kind of judgment (e.g. Prov. 3:5), so that there is such a thing as being guilty of it, yet the everyday judgments of reason are not necessarily committing this sin. A section on the “Office of Reason” in Charles Hodge’s Systematic Theology has been subjected to this very misunderstanding, most notably by Van Til.7 The basic objection was that Hodge said, “reason must judge of the evidence by which a revelation is supported.”8 But again, does this “judgment” mean the subjection of God’s word to the dictates of human reason, or does it simply mean that the rational soul has no other instrument by which to recognize the logic of the facts? In the section on the nineteenth Princeton theologians, I will argue that Hodge simply meant the latter. 

This second class of reason as a human activity includes reason as mode or even source, as in the expression “truths of reason.” That is also a slippery term for roughly the same reasons. At this exact point we need to factor in two concepts that range from the widely accepted to the more controversial. These are what are commonly called discursive reasoning and autonomous reasoning. We must test whether or not the sense we all invest in these terms has the same referent. 

Discursive reasoning simply means ordinary sequential thinking, whether deductive or inductive. On the basis of some idea regarded to be true, other implications follow. On the same basis, new questions and goals begin to form that would be otherwise if alternative more basic truths were seen to be the case. In short, discursive reasoning is learning reasoning; but for the same reason, it also makes mistakes. Only God knows all as in an instant. Our reason is a process. There is no controversy about the meaning of this term. The disagreement will arise over its propriety as a source of foundational knowledge. On the human level, the opposite of knowledge arrived at by discursive reason is intuitive knowledge. To experience an intuition is to receive a whole idea as a complete package, so to speak. We can see why this would be an attractive candidate for the only mode in which one is said to “have knowledge” in revelation.

Now when it comes to this expression “autonomous reasoning” there is a fair amount of speaking past each other. The modifying adjective itself simply means “self” (auto) “law” (nomos). When presuppositionalists use this term, they mean the notion of reason set up as the final judge and standard for whether something is true: a posture in which one will not have God as authority, but only one’s own reason. 

In a recent essay, John DePoe makes the case for autonomous reasoning. As one would guess, he operates off of a different sense of the term “autonomous” than those following Van Til. He defines it simply as “an individual taking personal responsibility for what he believes.”9 He also mentions the popular version of this, “to think for oneself,” which for many people does not mean to consistently apply the same instrument of thought to the claims of authorities, but rather to reject the authorities out of hand. It is evident that DePoe does not mean the anti-authority popular version. He then turns to the presuppositionalist conception:

“presuppositionalists believe that to allow human reason to weigh the evidence in determining whether the Bible is God’s Word is to place man’s reason as an authority over God and His Word.”10

If this is a correct assessment of the presuppositionalist’s meaning, then their definition of autonomous reason needs to be made more specific. By this term is not meant merely reasoning as if God’s truth did not stand over every area of thought. The idea is actually that if reason grounds any theological or exegetical conclusion in any extra-biblical premise or body of evidence, then that standard is now the authority over God’s word. 

For Bavinck, the “principle of autonomy” is a bit more sophisticated, but also more general. It is the position that the world (and man) can get on well enough without God, and therefore without revelation subsequent to the original creation. What began in Deism was then bound to undergo a total revolution toward full Atheism. The implication for epistemology is that supernatural revelation and natural autonomy exists on two poles and can admit of no middle ground without that ground turning into a slippery slope.11 This is something to keep a close eye on in studying Bavinck because you will recall in our discussion on revelation that he was most adamant that the supernatural-natural breakdown was misguided; yet here he is sensitive to denying ground to “natural” man’s foundational principles. We will see how this plays out later. 

It is not as though the Van Tillian tradition is the only group that has such a category. The more longstanding term “unaided reason” in non-Reformed authors comes to mean the same thing. The idea in both is that the human reasoning process is either (a) independent of divine revelation, or else (b) intentionally avoiding any explicit biblical grounding for conclusions, or else (c) both, with the connotation that (a) and (b) are inseparable. The classical view rejects (c), acknowledges that many projects have self-consciously engaged in (b)—Anselm’s Cur Deus Homo and C. S. Lewis’ moral argument in Mere Christianity being famous examples—but maintains that (a) is strictly impossible and only attempted as a rationalistic pretension. Without this exact breakdown, authors who use such expressions without further nuance are only perpetuating sloppy thinking and unwarranted mistrust for the ordinary relationship between reason and objective natures.

Two examples of the expression used in this way will suffice. Robert Audi wrote in The Cambridge Dictionary of Philosophy,

“According to Aquinas ... the existence of God and some things about the divine nature can be proved by unaided human reason, but such distinctively Christian doctrines of the Trinity and Incarnation cannot be thus proved and are known to humans only because God has revealed them.”12

Note the way that the assumed term is defined for us by means of the contrast to its opposite “known … only because God has revealed them.” The student who runs into a dozen or so instances of this unchallenged contrast will quickly form the idea that there is an inverse relationship between rational demonstration and recognizing the superiority of those truths revealed.

From a Christian perspective, Demarest gives a similar impression:

“Postulating the existence of an ‘analogy of being’ between God and man, classical Thomistic theology maintained that unaided reason, by reflecting on the sensibilia of the created order, is capable of informing man both that God is and what God is like.”13

Yes, Thomas did indeed speak of a natural theology that delivered on such knowledge; but in what sense exactly is this reasoning about objective natures “unaided” by the grace of revelation? We will see in our section on medieval natural theology that Aquinas would have entertained no such thing. 

A third example comes from one who operates in the Thomist tradition and in no way means to marginalize the activity. Ralph McInerny writes of the many believers who “reject the notion that there is a way whereby sinful man can arrive at truth about God, even simply that he exists, by unaided human reason.”14 This example should be added in fairness to show that the idea is so pervasive that even the friends of the activity have learned to accept the pigeon-holed description.

Reason as a Completed Set, or Product, of that Activity

Third, reason refers to a completed set, or product, of the aforementioned activity. We could think of this as either a constructive unit, or a larger theoretical body of knowledge. In other words, sometimes the word “reason” will be used to refer to “what we know” as the result of thinking. It could be uttered as a common or even practical rationale: e.g., “My reason for telling her was so that she would be informed.” Or, as a way of expressing more formal logical grounds: e.g., “The reason that we concluded no justice would be served is that the judges are all corrupt.” 

Clearly this third, substantive sense of reason will presuppose a working definition of knowledge as well. Even to the degree that “x amount” of the members of that set of “knowledge” is true, the question as to how this helps the mind judge on some additional truth is not yet dealing with a settled knowledge but only to a provisional set, something analogous to the distinction in science between data and laws. At any rate, human reason discovers truth; it does not determine the truth. Even the larger sets of objective knowledge by which we say that something is “contrary to reason,” even this knowledge is provisional, and thus the “reason” we ascribe to it is only in a relative manner of speaking.

So when we speak of human reason (whether as procedure or product) “determining” what is true, or rendering a judgment on that truth, clearly we must mean this only in a secondary or subjective sense. It is somewhat ironic for Protestants to misconstrue this, given the very similar charge by Rome about the doctrine of the private interpretation of Scripture. It was slandered as individual autonomy: as many interpretations as there are Bible readers. We understand that Luther et al meant nothing of the sort. On the contrary, the “private” dimension referred not to the creation of truth, but to the liberation of the conscience to discover and live by it. 

Reason as a Transcendent Principle

Fourth, reason refers to a transcendent principle. Classical thought introduces us to this sense where the old thinkers referenced “the Divine Reason,” whether in the appeal of various Greek schools to the logos, or as it was appropriated in the earliest Christian thought. In the terms of Platonic realism, it is this being of Reason in which all finite acts of reasoning are participating whenever such may be called “right reasoning.” Put slightly different, an act of right human reason is the mind conforming to the Divine Reason.

This most objective sense of the idea of Reason may be witnessed on a popular level as late as in Chesterton and Lewis. Thus, “The part he doubts is exactly the part he ought not to doubt—the Divine Reason,”15 or “It is therefore obvious that sooner or later you must admit a Reason which exists absolutely on its own. The problem is whether you or I can be such a self-existent Reason.”16

This concept has also been closely associated with “the light of nature,”17 or in the Thomistic explanation of how natural law is “participation of the eternal law in the rational creature,”18 or further back in Augustine’s concept of divine illumination.19 In other words, these were ways of describing the immutable laws of thought.20 This accords with the objective sense of reason that was spelled out by Turretin:

“Human reason is taken either subjectively for that faculty of the rational soul by which man understands and judges between intelligible things presented to him (natural and supernatural, divine and human); or objectively for the natural light both externally presented and internally impressed upon the mind by which reason is disposed to the forming of certain conceptions and the eliciting of conclusions concerning God and divine things.”21 

There are also legitimate hybrid uses of the word, and then again downright confusion. Gordon Clark seemed to relate our second and fourth uses for the purpose of combating an empiricist version of the third. He wrote that,

“reason may well be defined as logic … When a Christian theologian is deducing consequences from Scriptural premises, he is reasoning – he is using his reason. To require him to test Scripture by sensation in order to avoid the charge of irrationality is itself irrational prejudice.”22

Clark took exception to so-called autonomous reason for the same reasons as Van Til. However, his affinity for the science of logic and its application in his dogmatic method23 allowed him to make an exception for the substance of formal thinking. What really exalted human reasoning over Scripture, according to Clark, was not the all-pervasiveness of logic but rather the demand that all truth claims be empirically tested. This is an example of a more systematic hybrid of reason.

What about more popular usage? Expressions such as “Reason tells us” and “according to reason” are mostly unhelpful as they assume a universal consensus about a faculty that is individual. There may indeed be consensus here or there, but to call that “reason” is a fine way to stifle reason, as it sends the message that in order to be rational everyone ought to conform to the present majority opinion on every matter. The same verbal mischief can take on an even more triumphalist note, as it did in the Enlightenment’s persistent declaration that “X is an offense to reason” or even in the pretentious title “the Age of Reason.”

More confusion enters into our definitions of reason when we are situating fallen reason to reason per se. Owen Anderson comments,

“It is often maintained that ‘human reason’ is corrupt, or is different from God’s reason. This is true if by ‘reason’ it is meant ‘reasoning,’ or ‘thinking process.’ But here ‘reason’ refers to the laws of thought which cannot be corrupt (as if a is a—the law of identity—were changed after the Fall), and they are universal for all thinkers.”24

This particular confusion will become important when we examine the fideist objections to rational foundations. Most iterations of fideism will make this “fallen reason” central to their critique. The notion that there is something like an essential reason that is unaffected by the fall is anathema to such a view. At best one can speak of a pristine, or original reason, which may indeed be subject for redemption, but which cannot be foundational in the movement from the natural mind to the truths of special revelation. 

The goal of this excursion into the meanings we assign to reason is simply to show that there are different legitimate uses. On the other hand, just as with revelation, there are inaccurate ways to use these in contexts where they do not apply. Crucial to matching the right use to its proper context is seeking clarity on those other words which either apply or modify or situate reason, whether “judgment” or “autonomous” or “unaided” or “fallen” or “according to” and so forth.

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1. Paul Helm, Faith & Understanding (Grand Rapids: Eerdmans, 1997), 5.

2. Peter A. Angeles, The HarperCollins Dictionary of Philosophy: Second Edition (New York: HarperCollins Publishers, 1992), 255.

3. McClean in Green and Starling, ed., Revelation and Reason in Christian Theology, 184.

4. John Calvin, Institutes of the Christian Religion, I.3.1.

5. Francis Turretin, Institutes of Elenctic Theology, I.1.3.11.

6. Helm, Faith & Understanding, 6-8.

7. Cornelius Van Til, Christian Apologetics (Phillipsburg, NJ: Presbyterian & Reformed Publishing, 2003), 102-106.

8. Charles Hodge, Systematic Theology, Volume I: Theology (Peabody, MA: Hendrickson Publishers, 2008), 53.

9. John M. DePoe, “The Place of Autonomous Human Reason and Logic in Theology,” in David Haines, ed., Without Excuse: Scripture, Reason, and Presuppositional Apologetics (Leesburg, VA: Davenant Press, 2020), 53.

10. DePoe, “The Place of Autonomous Human Reason and Logic in Theology,” 54.

11. Herman Bavinck, Philosophy of Revelation (Peabody, MA: Hendrickson Publishers, 2018), 8-9.

12. Robert Audi, The Cambridge Dictionary of Philosophy (Cambridge: Cambridge University Press, 1995), 607.

13. Bruce Demarest, General Revelation, (Grand Rapids: Zondervan, 1982), 20.

14. Ralph McInerny, Praeambula Fidei: Thomism and the God of the Philosophers (Washington, D.C. The Catholic University of America Press, 2006), 3.

15. G. K. Chesterton, Orthodoxy (New York: Image Books, 1990), 31.

16. C. S. Lewis, Miracles (New York: Simon & Schuster, 1996), 40.

17. Westminster Confession of Faith, I.6

18. Thomas Aquinas, Summa Theologica, II-1, Q.91, Art.2

19. Augustine, Confessions, IV.15.25, V.6.10; cf. F. C. Copleston, Medieval Philosophy (New York: Harper Torchbooks, 1961), 20; Étienne Gilson, The Christian Philosophy of Saint Augustine (Providence: Cluny Media, 2020), 109, 122, 126-27.

20. Owen Anderson, The Clarity of God’s Existence: The Ethics of Belief after the Enlightenment (Eugene, OR: Wipf & Stock, 2008), 42.

21. Turretin, Institutes, I.1.8.1

22. Gordon Clark, Christian Philosophy (Unicoi, TN: The Trinity Foundation, 2004), 181.

23. Clark, Christian Philosophy, 17-20; 86-103.

24. Anderson, The Clarity of God’s Existence, 42.