The Moral Argument for God’s Existence: Some Thomistic Natural Law Musings

In continuing my discussion on theistic arguments, I would be remiss if I said nothing about the moral argument—surely the most popular argument for God’s existence currently making the rounds. Perhaps the most familiar, cogently set forth, and adroitly defended version of the moral argument is by the eminent contemporary Christian philosopher, apologist, and scholar William Lane Craig.[1] His common formulation of the argument is: 

  1. If God does not exist, then objective moral values do not exist.
  2. Objective moral values do exist.
  3. Conclusion. Therefore, God exists.

The only ones who could take exception to the form of the argument would be those who do not understand basic formal logical schemata. This argument form is known as a modus tollens (Latin for “mode of denial”). It is also known as denying the consequent. In a material implication, the denial of the consequent logically entails the denial of the antecedent. Thus,

p ⊃ q                      [which reads: “If p, then q”]
~q / ∴ ~p              [which reads: “Not q. Therefore not p.”]

As it stands, I believe there can be no objection to the argument. However, I know that those who advance this argument would likely have a problem with my prima facie reading of it. It is undoubtedly true that if God does not exist, then nothing else would exist, including moral values, objective or otherwise. In this respect, this moral argument “collapses” into a cosmological argument.[2] But this is not why the defenders of this moral argument offer the argument in the first place. For them, the causal connection between God and objective moral values is not merely ontological in this respect. (I will leave aside whether the relationship intended by the argument between God and objective moral values is a causal one.) Instead (the argument seems to go), even if (per impossible) there could be a world with humans but without God, this world would necessarily be absent any objective moral values.

But is this the case? Does morality need God? I submit that in the tradition of Natural Law Theory, the answer is ‘yes’ and ‘no’.[3] I shall not take the time here to flesh out too many details about Natural Law Theory.[4] Only a few points are needed to jump directly to how the ‘yes’ and ‘no’ answers follow from Natural Law Theory.

Regarding the ‘no’ answer, a few things need to be unpacked. First, the moral argument sometimes traffics in the language of whether morality can be objective without God and sometimes it traffics in the language of whether there could be morality at all without God. Framing the argument in the latter way is what gives rise to my prima facia response above. Framing it in the former way avoids the problem of trying to defend the existence of something absent God’s existence in this prima facie reading. It also allows for the important distinction between the epistemology of morality (knowing that something is moral/immoral) and the ontology of morality (what it is that makes something moral/immoral). But in an important sense, one might argue that the question of the objectivity of morality and the question of the ontology of morality are really the same practically speaking, since it would be difficult to distinguish morality without objectivity from abject moral relativism or even from moral nihilism. I will leave this discussion aside for our purposes.

Second, the Natural Law tradition is grounded in the metaphysics of Aristotle with the significant augmentations from Aquinas both metaphysically and theologically.[5] Only a few of these metaphysical points need to be introduced to sketch out the way in which Natural Law would give the ‘no’ answer to the question of God and morality. Here is the short version. The “good” for X is the perfection of X as the potentialities of X are made actual, i.e., as they are made real. To be made real just means to come into being. A thing’s perfections just are that thing’s increase in its being.[6] These potentialities of X are what they are precisely because of the nature of X. A “good” knife has a sharp blade because that is what a knife is. It would make no sense for someone to protest “who are you to say that a knife ‘ought’ to have a sharp blade?” What it is to be a knife is to have a sharp blade, which is to say that it is of the “nature” of a knife to have a sharp blade. (I put the word ‘nature’ in scare quotes to signal the fact that, strictly speaking, artifacts such as knives do not have real natures.” One should be able to see the basics of Aristotle together with the fingerprint of Aquinas in these few points—act and potency, final causality (teleology), form and matter, natures as a metaphysical reality, and Aquinas’s understanding of existence as an act.

Given that what is good for X has proximately to do with X’s nature, then the objectivity issue is quite straightforward. Human goodness is defined in terms of human nature. Given (in Aquinas) that human nature is an objective fact of reality, then human goodness is an objective fact of reality. To deny the objectivity of morality in the absence of God would be like denying the objectivity of gravity in the absence of God.

But something is still missing here. To define the good for a human in terms of human nature has not yet risen to the level of moral goodness. The failure to recognize the distinctions between ‘good’ and ‘moral good’ can be the source of some confusion among the detractors of Natural Law Theory. One can begin to grasp the significance and distinctiveness of human moral goodness when one identifies why it is that we regard humans as guilty for wrongdoing and yet do not regard animals for wrongdoing in the same way. In Aquinas, morality is unique in humans among sensible creatures on earth because only humans have rationality, free will, and are able to desire the good for its own sake.

To be sure, quite of bit of philosophy has been telescoped here. All I can do at this point is to suggest some readings.[7] The up-shot is that, in Natural Law Theory, human morality has quite a bit of objectivity given human nature, human rationality, human free will, and the human’s pursuit of the good as such.

As for the ‘yes’ answer, I have mentioned above that morality would need God ultimately because everything else needs God in order to exist.[8] Thus, for there to be human morality, there would need to be humans. But for there to be humans, there would need to be God. This point is keenly made by the metaphysics of Aquinas. For Aquinas, God does not HAVE existence. Instead, God IS existence. God is a being whose very essence is His own existence. This is what some theologians mean by saying that God is self-existent, also known as God’s aseity.[9] God exists by virtue of being ipsum esse subsistens—substantial existence itself. Everything else that exists only has existence, which is to say, its existence is given to it and does not arise from its very nature.

Understandably, certain ones are critical of taking the moral argument as seemingly being nothing more than a roundabout cosmological argument. But in the metaphysics of Aquinas, there is more going on here than the critic might suspect. It is not merely the fact that, since morality needs humans and humans need God, then morality needs God. Rather, there are important details that are nested in exactly what it is about humans as God has created us that gives rise to morality. I have already mentioned a few specifics about the metaphysics. One can add that the teleology of humans comes from God. This is why Aristotle can have human teleology and yet never connect it to his Unmoved Mover as efficient cause. While in Aristotle the Unmoved Mover is the telos of all of the universe, it itself is not the efficient cause of that telos (nor, indeed, of the universe either). For Aristotle, the telos is just an eternal fact of reality. But in Aquinas, it is not only the case that humans have the telos we have because of the nature we have (intrinsic teleology), but, given that God is the creator of that nature, God is also the creator of that telos (extrinsic teleology).[10] God has created us to aim toward particular goods in this world like survival, procreation, and social flourishing. But He has also created us to aim toward Him as our ultimate good.

There is, perhaps not surprisingly, more to say about the ‘yes’ answer. I have said nothing by way of explanation about the notion that humans are unique in our pursuit of the good as such. I said neither what exactly is the “good as such” nor how that figures in to the notion of moral obligation. But to balk at what has been said as being nothing more than a “collapsed” cosmological argument misses how powerful this notion of morality is.

Many apologists with whom I am familiar employ a number of findings of contemporary science to leverage various arguments for God’s existence, including the fine-tuning of the universe, the information content of the DNA molecule, and the irreducible complexity of biological systems. (Let me remind the reader that I celebrate these arguments, despite the limitations I and others have argued they have.[11]) Nowhere do I hear these apologists frame the argument as “if God does not exist, then objective fine-tuning does not exist” or “if God does not exist, then objective information does not exist” or “if God does not exist, then objective irreducible complexity does not exist.” Indeed, I am not sure exactly how one would even take the notion that, without God, there is no (for example) “objective” information. It would seem that most people would maintain that even if (per impossible) God did not exist, there would still be objective fine-tuning, information, or irreducible complexity. Now, to be sure, some might object and exclaim “no!” for it is precisely the argument that God is the only viable explanation for how and why there is fine-tuning, information, or irreducible complexity. But this objection just shows that, in some sense of the term, God is the cause of the EXISTENCE of these features. But to argue here that God is the cause of their existence says nothing about their objectivity. It is only to admit that these arguments are some species of the cosmological argument, broadly construed. The “objectivity” of fine tuning, information, and irreducible complexity is completely understood along the contours of the laws of physics and mathematics. There is no need posit that, without God, these features would have no objectivity.

By analogy, this is what I’m doing with the moral argument. I am saying that there are objective features of realty (act/potency, teleology, form/matter, natures, existence) that account for the objectivity (and in an important sense the very existence) of morality irrespective of God. This is not merely an epistemological point. Just as there can be information without God at some level of consideration (e.g., specified complexity) there can be morality without God at some level of consideration (e.g., act/potency, teleology, nature, etc.) But the reader should notice that these metaphysical truths are the building blocks of the classical cosmological argument.[12] What one needs to account for morality at a proximate level, become the sufficient condition of the demonstration of God’s existence—and not only the existence of God, but almost all of the attributes of classical Christian theism. It would seem that the moral argument construed along Thomistic Natural Law lines is quite powerful indeed.V

[1] Craig’s argument is replete on the internet. Several samples from his website include and You Tube versions can be found at (pt. 1), (pt. 2), (pt. 3), and (pt. 4).

[2] In a podcast (available at, accessed 04/17/18) Craig leveled this very criticism of this Thomistic Natural Law formulation that I gave in a presentation at the National Conference on Christian Apologetics in October of 2016 titled “Rethinking the Moral Argument: How Does Morality Depend on God?” Craig’s critique was based on The Christian Post (an on-line Christian newspaper) article which is available at, accessed 04 /17/18.

[3] I am indebted to Edward Feser for spurring on my interests in this topic with his “Does Morality Depend on God?” (, accessed 03/26/18). I owe much of my thinking to his insights but I do not want to necessarily implicate him in everything I have to say on this subject.

[4] See my paper “God and Morality” available at, accessed 04/17/18.

[5] My take on Aquinas’s doctrine of Natural Law is a fairly common one but is not without its critics. See footnote 6 of the paper cited in endnote 4 above.

[6] This important notion is what explains how it is that ‘being’ and ‘good’ are convertible terms in Aquinas’s (and other’s) thinking. See Jan Aertsen, “The Convertibility of Being and Good in St. Thomas Aquinas,” New Scholasticism 59 (1985): 449-470. Since being and good are convertible, then the Supreme Being is the Supreme Good. For Aertsen’s treatment of this issue of the medieval doctrine of the transcendentals vis-à-vis Aquinas see his Medieval Philosophy and the Transcendentals: The Case of Thomas Aquinas (Leiden: Brill, 1996). For his fuller treatment of the transcendentals in Medieval philosophy see his Medieval Philosophy as Transcendental Thought from Philip the Chancellor (ca. 1225) to Suàrez (Leiden: Brill, 2012).

[7] One such reading should be John Knasas, Being and Some 20th Century Thomists. New York: Fordham University Press, 2003, pp. 248-272.

[8] It is significant to note here that I am not merely saying that everything else needs God in order to have come into existence at the beginning (as the Kalam cosmological argument would say). I think this is true enough. I hold that the Kalam Cosmological argument is sound. Aquinas, however, did not (see his Summa Theologiae I, Q46). Rather, in Aquinas’s thinking everything else needs God in order for it to exist at any moment of its existence. God is not merely the cause of everything else’s coming to be, but God is also the current cause of everything else’s continual be-ing. As an illustration, this of the difference between a carpenter who causes a wooden chair to “come into existence” vs. the musician who is continually causing his music to “continually exist.”

[9] One should not press the Latin too far (a, “from” and se, “itself, himself”) as if to say that God’s existence is self-caused. Such a notion is incoherent. Instead, to say God’s existence is “from” Himself is to say (or at least allows it to be said) that God’s existence is His essence. He exists by virtue of His nature.

[10] For a helpful reading, see Edward Feser “Teleology: A Shopper’s Guide” in Neo-Scholastic Essays (South Bend: St. Augustine’s Press, 2015): 28-48.

[11] Classical theists would contend that these arguments do not (without significant augmentation) demonstrate the attributes of God. Some might even go so far as to say that these arguments point away from (rather than merely understate) classical theism. As I have said elsewhere, in using these other arguments in light of being a Thomist, I take refuge in the words of Joseph Owens. “Other arguments may vividly suggest the existence of God, press it home eloquently to human consideration, and for most people provide much greater spiritual and religious aid than difficult metaphysical demonstrations. But on the philosophical level these arguments are open to rebuttal and refutation, for they are not philosophically cogent.” [Joseph Owens, “Aquinas and the Five Ways,” Monist 58 (Jan. 1974): 16-35. The quote is on p. 33.]

[12] For a discussion and more details on how such philosophical doctrines are the necessary ingredients of the science that many atheists tout and yet are also the sufficient ingredients of the demonstration of the very God those atheists deny, see Edward Feser, The Last Superstition: A Refutation of the New Atheism (South Bend: St. Augustine’s Press, 2008).


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s