Learning to Doubt Your Doubts: A Response to Dr. Brian Mattson

Written by Adam Tucker

posted by Southern Evangelical Seminary

In recent months, there seems to have been an increase in the number of presuppositional and/or reformed brothers and sisters criticizing various ideas of Thomas Aquinas (a.k.a. Thomism), the thirteenth century Catholic philosopher and theologian. There are many, evangelicals included, who consider themselves “Thomists,” meaning they hold to the foundational philosophical ideas taught by Aquinas and the classical view of God that follows from such thinking. I happen to consider myself an evangelical Thomist. To be clear from the outset, that does not mean a Thomist must ascribe to every idea propounded by Aquinas.

I do not pretend to speak as an ultimate authority on these matters, but as someone who does hold a Masters in Philosophy from a thoroughly Thomistic institution, I hope my thoughts will be taken seriously. There are adequate responses to many of the recent criticisms raised by some of our brothers and sisters (see HERE and HERE). However, I wish to respond specifically to a RECENT BLOG POST by Dr. Brian Mattson regarding Aquinas and natural law theory.

Before going forward, we need to clear away one hurdle I often see used in critiques of Thomism, and Mattson’s critique is no exception. The charge is leveled that there are “many interpretations of Aquinas’ teachings” (natural law in this case) and that nearly 1,000 years of thinking about these issues has not settled the matter. This rhetorical point is supposed to call into question any particular view of Thomism because, well, there are just so many interpretations of Aquinas. But this does not follow at all. This rhetoric bears a striking resemblance to skeptical arguments against Christianity. After all, it has been 2,000 years since the beginning of Christianity, and, well, look at all the denominations and divisions within Christianity. Therefore . . . ? Such thinking is fallacious. The fact that there are differences in interpretation does not entail that no one has a correct interpretation. In fact, those critiquing Aquinas are quite sure their interpretation of Thomism is correct. Mattson lists several areas of contention regarding his understanding of Aquinas to which I wish to briefly respond.

Rationally Compelling Reasons

First, for those unfamiliar, natural law is based on the idea that what is good for a thing is that which fulfills the thing’s nature (i.e., what it is). What fulfills a thing’s nature is realizing the ends/purposes (i.e., the telos, or teleology) towards which the thing is directed (e.g., a good eye is one that sees well). Mattson says, “Forgive me for pointing this out: talking about an ‘intrinsic teleology’ or ‘proper ends’ that we can rationally discern is every bit as unpopular with our cultured despisers as quoting John 3:16. Teleology is precisely what our culture denies.” I do not disagree at all. That is indeed the problem. Our culture has adopted bad philosophical views that have led to our current state of moral relativism and confusion. Ignoring these erroneous views, however, and jumping straight to God does not help matters.

Most of the time, going to straight to God on moral issues improperly grounds the very morality being discussed. Even if the person with whom we are discussing these matters accepts our appeal to God, he would then be bringing his erroneous views of reality to bear on Christianity. This is precisely what has happened for the last several hundred years, and the current intellectual state of the church is deplorable. If one rejects the ability to know basic things about sensible reality (e.g., the good of an eye is to see well), he has removed any rationally compelling reason for believing in God as well. Thus, the culture (and often times the church) concludes that one must “presuppose” (i.e., assume) the existence of God, resort to blind faith, or find rest in his own skepticism. I am convinced the presuppositionalist has adopted the fundamental tenants of the bad philosophy he claims to be combating.

Adopting Bad Philosophy

To see why, consider Mattson’s second contention. He says, “Scratch a truth claim deep enough, and you’ll uncover a faith commitment at the bottom. That’s because we are dependent creatures who literally have no autonomous, independent place on which to epistemically stand.”1 Such a view, I think, is based on a misuse of the word “faith” and the assumption that man does not directly know sensible reality (the very cornerstone of modern philosophy). Since the time of Descartes, the modern view is that confidence in the reliability of our senses is something one merely assumes because we only know our thoughts about the thing we sense rather than knowing the thing in itself.

For example, consider these quotes from presuppositional apologist Greg Bahnsen:

“[The believer] views logic as rules of thought implanted in man’s mind by the Creator; the [unbeliever] sees logic as the self-sufficient, self-authenticating tool of autonomous man’s reason . . . The Christian and non-Christian will take different minds as the final reference point in their own thinking; the believer will use patterns of thought and interpretation provided by God while the unbeliever will derive them from the created world itself (e.g., his own mind).”2

He goes on to say,

“So the most fundamental premise of all autonomous science, the uniformity of nature, is neither empirically nor rationally justifiable! . . . If science proceeds autonomously, then the only thing that can be discovered in the world is man’s own interpretative and ordering activity; nature merely echoes back the thoughts of the autonomous man. Hence he ends up accepting his own revelation, based on his own authority [i.e., his own mind].”3

There is certainly no biblical reason to think about man’s knowledge in this way. In fact, considering the numerous miracles, appeals to nature, eyewitness testimony, and personal physical experiences, we seem to see some type of empiricism (knowing sensible things) assumed in the pages of Scripture. Moreover, space does not permit the numerous philosophical reasons for rejecting the modern view of knowledge. The point here is simply that Mattson and Bahnsen are reading their prior philosophical commitments into both Scripture and Aquinas. I contend it is their fundamental commitment to bad philosophy, rather than their (erroneous) accusation that Aquinas believes man to be “autonomous,” that forms the foundation from which these men offer their critiques.

Third, while implicitly denying our ability to know things in themselves, like most human beings, when it comes down to it, Mattson admits that we can actually know things. He says, “Now, of course unbelievers know lots of things and deploy their mental resources very successfully. I readily and thankfully admit it!” Bahnsen agrees when he says, “As a creature he can and does use his mind to know things; he is able to do so despite of what he thinks about his epistemological situation. As a creature he foremost knows God and is responsible to Him.”4 This is where I think the primary disagreement arises. I, as well as Aquinas, deny that God is what man “foremost knows.” Our mode of knowing is determined by our human nature. As human beings we foremost know sensible things, and from that knowledge we can reason to truths about natural law and even God’s existence (Rom. 1:20). We know this is true from both experiencing how humans come to know things and philosophical arguments for human knowledge.5 If it were impossible for man to naturally reason from premises, based on his knowledge of sensible reality, to conclusions that reach beyond the sensible world, then he would have no way to think about much of anything that is really interesting. As Aquinas says,

“The existence of God and other like truths about God, which can be known by natural reason, are not articles of faith, but are preambles to the articles; for faith presupposes natural knowledge, even as grace presupposes nature, and perfection supposes something that can be perfected. Nevertheless, there is nothing to prevent a man, who cannot grasp a proof, accepting, as a matter of faith, something which in itself is capable of being scientifically known and demonstrated [note: this is the classical understanding of science as a body of knowledge about a particular subject].”6

Mattson lists several Scripture passages to support his view that man cannot naturally know things about God. But these passages indicate either man’s willful condition of not following the evidence where it leads so to speak, or man not accepting the truths of the Gospel, which I would argue is not something man can naturally reason to in the first place. But for Aquinas, the ability to know some bit of sensible reality, which both Mattson and Bahnsen admit is possible, is the only starting point he needs. Our knowledge of sensible reality, to whatever extent, is evident to us. It is not an assumption that can be rationally denied, nor does it need arguing for since it is a first principle of human knowledge. If man can know truths about sensible reality, then he is on his way to understanding both natural law and arguments for God’s existence.

Anything but Autonomous

When we know things, we know the nature of things. Because we can know the nature of things, we can know what is good for those things. This is the very foundation of natural law reasoning, and it is an extension of our shared common everyday experience of knowing sensible reality. This does not entail, however, that man’s reasoning is “autonomous” or “unaided” in the sense that folks like Mattson and Bahnsen use those terms. Man can know things because of his human nature, but man only exists with such a nature because God created him with it. Again, Aquinas says,

“Now every form bestowed on created things by God has power for a determined act, which it can bring about in proportion to its own proper endowment; and beyond which it is powerless, except by a superadded form, as water can only heat when heated by the fire. And thus the human understanding has a form, viz. intelligible light, which of itself is sufficient for knowing certain intelligible things, viz. those we can come to know through the senses. Higher intelligible things the human intellect cannot know, unless it be perfected by a stronger light, viz. the light of faith or prophecy which is called the ‘light of grace,’ inasmuch as it is added to nature. Hence we must say that for the knowledge of any truth whatsoever man needs Divine help, that the intellect may be moved by God to its act. But he does not need a new light added to his natural light, in order to know the truth in all things, but only in some that surpass his natural knowledge. And yet at times God miraculously instructs some by His grace in things that can be known by natural reason, even as He sometimes brings about miraculously what nature can do.”7

Mattson says he wants to give “deep and ‘thick’ biblical and theological descriptions of reality.” This is precisely what I think Aquinas is doing. It is not a “thick” or “biblical” answer to say one must assume God’s existence and the whole of Christianity in order to truly describe some aspect of reality or converse with unbelievers about moral issues (eg. homosexuality, abortion, marriage, etc.). It is not a “thick” answer to appeal to mere divine command. Natural law helps us answer all of these questions with very “thick” responses.

In addition, if by “biblical” one means a teaching or truth that lines up with what the Bible says, then natural law gives very “biblical” answers. In doing so, one can then build a very powerful case for the existence of God. Why do humans exist with the natures they have? The only answer, I am convinced, is because God has created us as a natural kind with our specific human nature. God’s existence is a necessary condition for man to know anything at all because man would not exist, even for an instant, without God causing him to exist.8 Hence, man is utterly and completely reliant on God for everything. He is dependent upon God for the very nature he has (including his natural epistemic ability) and for the very continuance of his existence as God conjoins his essence/nature to an act of existence.

It is simply a misinformed opinion that would lead anyone to accuse Aquinas of divorcing faith and reason in a Kantian sense or making man “autonomous.” On the contrary, as Aquinas himself says,

“Now, since God not only gave existence to things when they first began to exist, but also causes existence in them as long as they exist, by preserving them in existence, as we have proved; so not only did He give them active forces when He first made them, but is always causing those forces in them. Consequently if the divine influence were to cease, all operation would come to an end.”9



1. According to Greg Bahnsen, “autonomous” means man “looks upon…his own laws or principles or experience [as] the final judge of truth and meaning.” Presuppositional Apologetics: Stated & Defended. American Vision, Kindle Locations 645-646. Kindle Edition.

2. Greg Bahnsen, Presuppositional Apologetics: Stated & Defended. American Vision, 2009, Kindle Locations 2229- 2243. Kindle Edition.

3. Ibid., Kindle Locations 2613-2647, Kindle Edition.

4. Ibid., Kindle Locations 638-640, Kindle Edition.

5. See Book 1, Chapters 9-12 of Aquinas’ Summa contra Gentiles.

6. Thomas Aquinas, Summa Theologica (Complete & Unabridged). Coyote Canyon Press, 2010, Kindle Location 711, Kindle Edition.

7. Ibid., Kindle Location 41843, Kindle Edition.

8. See Book 1, Chapter 13 of Aquinas’ Summa contra Gentiles and his small work On Being and Essence.

9. Thomas Aquinas, Summa Contra Gentiles, ed. Fathers of the English Dominican Province, (London: Burns Oates & Washbourne, 1924), 3:161-162.

Thank you to Dr. J. Thomas Bridges, Eric Gustafson, and Christina Woodside for their valuable feedback on this essay.


The subject matter of this article deals with approaches to Christian Apologetics. Learn more about this topic from our brand new 8-week online course, Christian Apologetic Systems, taught by Dr. Richard Howe.

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The views and opinions expressed in this article are those of the author and do not necessarily reflect the position of Southern Evangelical Seminary.

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