Hume's Classical Theism Dilemma

[Originally written for PHI 620 on Mar 6 2025]

David Hume’s Dialogues Concerning Natural Religion is without a doubt one of the most influential modern philosophical texts regarding God’s existence and natural theology more broadly. Since Hume’s day, debate about God’s existence has continued to rage in philosophical circles especially in the past half century in the anglophone world. One of the most hotly debated subjects within contemporary philosophy of religion, the subdiscipline of philosophy dealing with God’s existence and attributes, is the question of divine simplicity. In part IV of Hume’s Dialogues, Hume offers a dilemma regarding divine simplicity that can help shed light on the contemporary debate. In short, Hume’s dilemma is this: either divine simplicity is true (which Hume dismisses) or theism has no explanatory advantage over naturalism since both posit a kind of brute complex entity in order to explain contingent reality. In this essay, we will focus on the second horn of the dilemma and argue that on this count, Hume is correct and show how a denial of divine simplicity significantly undercuts any attempt to argue for God’s existence. In support of this claim, we will also see Hume’s dilemma repeated among two contemporary natural theologians.

Hume opens part IV of the dialogue with a critique of divine simplicity offered by Cleanthes who first asks Demea how his view, of God as simple, is any different from atheism since it posits a God who is utterly unintelligible and mysterious. Demea responds by showing that the other extreme, of making God too much like man, runs the risk of anthropomorphizing God and that a similarly pejorative label could be attached to Cleanthes’ view. In his response, Demea gives a good description of divine simplicity when he states:

According to [divine simplicity advocates], [God] sees past, present, and future in a single act; his love and hatred, his mercy and justice, are one individual operation; he is entirely present at every point in space, and exists completely at every instant of time. God’s nature doesn’t involve the slightest hint of difference or variation: there is no sequence of events in him, he doesn’t change, he doesn’t gain or lose anything. What he is now is what he has always been, and always will be, without any change in what he thinks, feels, or does. He stands fixed in one simple, perfect state; and it can never be correct to say that this act of his is different from that, or that this judgment or idea is one that he had only recently, and that it will in time be followed by some other judgment or idea.

Cleanthes then responds by saying that such a view is akin to atheism and is nonsense since it claims that God is mind and yet is unchanging which is an “abuse of words..” Thus, in Hume’s view it seems that divine simplicity amounts to nothing but nonsense. Claiming that God is a mind while claiming that he is utterly simple makes no sense and is no different than atheism since the God in question in no meaningful way resembles a god. It is beyond the scope of this paper to respond to Hume’s critiques of classical theism and so we will instead turn to the second horn of his dilemma.

Philo, the third character in the dialogue then proceeds to show the drawbacks of the alternative to divine simplicity, what Philo calls an “anthropomorphism.” Philo’s argument is that, if God’s thoughts are truly complex and not simple, then they stand in just as much need of an explanation as the complex material world and thus theism is no better than atheism in terms of explanation.

Philo begins by stating that a priori reason shows that “A mental world (or universe of ideas) stands in as much need of a cause as does a material world (or universe of objects); and, if the mental world is similar in its arrangement to the material one, their causes must be similar.” Then, when turning to experience, Philo states that both the material and mental worlds are alike in their need of explanation of thoughts and actions. Hence, if God’s plan is the cause of the universe it is entirely reasonable to ask what is the cause of this plan. If the theist attempts to cut short the explanation at this point, Philo argues that that is no better than cutting the explanation short at the material world. If God’s thoughts are complex, then, Philo argues, unless we cut explanation off at some arbitrary point, it will be turtles all the way down. Philo then takes up a possible response to his argument that is virtually identical to the response contemporary non-classical theists offer to such an objection.

This objection is that “The different ideas that make up God’s plan fall into order of themselves, and by their own nature.” In other words, whether contingently or not, there is a bruteness or inexplicability to this complexity in God. Philo retorts once again that such an answer may equally be given for the material world.

In response to this argument, Cleanthes tries to argue that a true explanation can be given for some phenomenon without it being an ultimate explanation: “is it any objection that I can’t assign the cause of that cause, and answer every new question that may endlessly be raised?” He then says that it is irrelevant if God has a cause or not, “You start abstruse doubts, complaints, and objections; you ask me, what is the cause of this cause? I don’t know, and I don’t care. I have found a God, and with that I stop my enquiry.”

Such a response by Cleanthes does nothing to sway Philo, however. He points out that appealing to a specific unexplained cause is not a good explanation and is not akin to what scientists do in explaining things:

Natural scientists indeed very properly explain particular effects by more general causes, even when these general causes themselves are in the end totally inexplicable; but surely they never think it satisfactory to explain a particular effect by a particular cause that is no more explicable than the effect itself. A system of ideas, arranged by itself without a prior design, is not a whit more explicable than a material system that attains its order in the same way; there is no more difficulty in the latter supposition than in the former.

In summary, Philo’s argument amounts to a dilemma: either God is simple or he is not. God cannot be simple because such a notion is utterly unintelligible and amounts to nonsense. If God is complex, then God is not a better explanation than the material world by itself since he too would stand in need of explanation. As we will see, this argument mirrors closely the argument today between classical theists, i.e. those who hold to divine simplicity, and so-called neo-classical theists, those who deny simplicity but affirm other traditional attributes of God such as omnipotence, omniscience, and so forth.

We will examine two contemporary philosophers, Edward Feser, a Thomist, and William Lane Craig, who denies divine simplicity, and show how their views mirror the debate between Philo and Cleanthes.

In his book Five Proofs of the Existence of God, Feser shows that various arguments for God’s existence point to an utterly simple God who is non-composite and purely actual. Feser here follows the classical line of thought going back to thinkers such as Thomas Aquinas, Augustine, and others in seeing God as the utterly simple ground of all reality.

In what sounds similar to Feser, Craig too will argue that God is the ultimate uncaused or unexplained creator of the universe and uses arguments similar to Feser’s. For example, Craig argues that the famous Kalam cosmological argument implies that the first cause of the universe must be uncaused, timeless, powerful, and personal. At first glance, Craig’s first cause and Feser’s first cause appear to be similar. However, Craig ultimately denies divine simplicity so that the superficial agreement remains superficial and not total. Because of this denial, Feser offers an objection to Craig’s theology that is very similar to the one Philo offers to Cleanthes.

In a review of Craig’s book on God’s aseity or self-existence, Feser notes, “Anything that is in any way composed of parts can exist only if something causes those parts to be combined. If God were not simple, he would need a cause—in which case, he would not be self-existent, contrary to divine aseity.” Thus, Feser thinks Craig’s theology is ultimately inconsistent: he affirms a supposedly self-existent but complex God which is incoherent. Undoubtedly, Hume’s Philo would give a similar reply to Craig.

Craig, of course, would and has argued that divine simplicity is itself a doctrine fraught with problems and indeed goes so far as to say in his recently published systematic theology that “Contemporary efforts to defend divine simplicity have become increasingly desperate and far-fetched” and that those who defend such a view “are doing no favor at all to Christian theology and spirituality.” Craig’s dismissal of the doctrine mirrors Cleanthes’ dismissal of divine simplicity. How then does Craig attempt to escape Hume’s dilemma with regard to divine simplicity?

Craig would object to the view that seeing God’s existence as necessary while not affirming divine simplicity is akin to atheism. Rather, Craig attempts to draw a distinction between bruteness, something that is simply unexplained and what he calls a “necessity of nature” or what he otherwise calls metaphysical necessity. Craig does not think that God’s existence is in any way unexplained but that “existence is part of the very essence of God.” How might we briefly assess Craig’s attempted navigation out of Hume’s dilemma?

Craig’s view seems to raise another dilemma that leaves him ultimately in the same place. If we grant that “necessity” can be attributed to a thing’s existence, even if that thing is not being itself, as a classical theist would hold, then it is reasonable to ask why the atheist cannot claim that the universe is necessary in order to “explain” its existence. On the other hand, it might be argued that if “existence is part of the very essence” of something, then that thing just is the very act of existence itself, i.e. the God of classical theism. Thus, it seems, Craig’s attempted explanation still yields Hume’s original dilemma, one between classical theism and an explanatory stalemate with atheism.

David Hume, it seems, grasped a key debate in natural theology well in his dialogue. The debate over divine simplicity is central to any attempted natural theology. If divine simplicity is denied, then the alternative view posits a non-simple God to explain all of reality. Such a complex entity seems itself to stand in need of explanation. Thus, the denier of divine simplicity’s attempted explanation satisfies neither the classical theist nor the atheist. Hume’s dilemma lives on today among two of the leading English speaking Christian philosophers of religion: William Lane Craig and Edward Feser. While both argue that God is the ultimate explanation of reality, they do so in distinct ways, each critical of the other’s approach and each open to different objections from the atheist. This is not to say that no advance in philosophy has been made since Hume’s day, but rather to show the enduring state of Hume’s dichotomy and its relevance for contemporary natural theology.

Craig, William Lane. Systematic Philosophical Theology Volume I: Prolegomena, On Scripture, On Faith. Hoboken: NJ, Wiley Blackwell, 2025.

–––, “The Kalam Cosmological Argument” in The Blackwell Companion to Natural Theology. Oxford, Blackwell, 2012.

–––, “#861 Is God’s Existence a “Brute Fact?” at Reasonable Faith, 12 November 2023, at reasonablefaith.org

Feser, Edward. “Keep It Simple” First Things (April 2020) at https://firstthings.com/keep-it-simple/

–––, Five Proofs of the Existence of God. San Francisco: CA, Ignatius Press, 2017.

Hume, David. Dialogues Concerning Natural Religion ed. Jonathan Bennett 2017 at earlymoderntexts.com