The book, Does God Exist? The Craig-Flew Debate, contains a transcript of the debate between William Lane Craig and Antony Flew, responses by eight commentators, and final responses by Craig and Flew. Many of the commentators, including some of the theists, sharply criticized Craig’s moral argument for God’s existence because, they argued, some moral truths are necessary truths and so do not need an explanation. Let’s call this objection UNMT (for ‘Unexplained Necessary Moral Truths’).

In his reply to commentators, as I read him, Craig replied as follows: (i) Christian theists who press the UNMT objection do not believe that God’s existence is logically necessary, whereas “the mainstream Christian tradition has held that God’s existence is broadly logically necessary, so that He can be the explanatory basis of necessary truths” (169). (ii) Necessary truths can stand in relations of explanatory priority to one another; indeed, there is such a thing as “explaining that (or why) a necessary truth is true” (169).

Allow me to explain. Let’s start with (i). Assume for the sake of argument that the proposition, Objective moral values exist, is true in every possible world but that the proposition, God exists, is not true in every possible world. In that case, God couldn’t be the explanation for objective moral values, since it would be impossible for a contingent truth (in this hypothetical, God’s existence) to explain a necessary truth (the existence of objective moral values). This hypothetical shows that, in order for it to be even possible for God’s existence to explain the existence of objective moral values, God’s existence has to be necessary. In other words, “Theism expresses a necessary proposition,” is itself a necessary (but not a sufficient) condition for God’s existence to explain necessary truths, including necessary truths about the existence of moral values.

As software engineers might say, this is a bug, not a feature, in Craig’s moral argument for God’s existence. If Craig’s moral argument requires that theism be a necessary proposition, then it is much more likely that theism is necessarily false (and so God cannot be the explanation for necessarily existing moral values) than that theism is necessarily true (and so it is possible that God might be the explanation for necessarily existing moral values). Why? Purdue University philosopher Paul Draper explains the point well.

Suppose that theism is not a contingent proposition. Then it is much more likely that it is necessarily false than that it is necessarily true. This is made clear by any objective comparison of the available reasons for thinking that theism is necessarily true to the available reasons for thinking that it is necessarily false. The former are limited to various versions of the ontological argument, which is almost universally rejected by philosophers. Indeed, even Plantinga admits that this argument fails to prove its conclusion. The latter include a whole host of serious arguments for the incoherence of theism. Keep in mind that I’m not convinced by these arguments for the necessary falsehood of theism, but they are clearly more persuasive collectively than the notoriously unpersuasive ontological argument. Further, theism asserts that the natural world was created by an omnipotent, omniscient, and morally perfect person, which assumes, not only that there is a maximum possible degree of power, knowledge, and moral goodness, but also that these three attributes are compatible with each other and with the existence of natural entities. Even ignoring specific arguments, clearly it is much more likely that some hidden incoherence lurks in the assertion that there exists a creator of nature possessing the highest possible degree of several distinct scaling properties than in the simple assertion that no such creator exists. Therefore, if I am mistaken and theism really is a necessary proposition, then it is very probably a necessary falsehood, which means that my assumption in my opening case that it is a contingent proposition is not only dialectically appropriate (for the reasons given in the previous paragraph), but dialectically generous. (LINK)

But let’s put that to the side and assume that God’s existence really is broadly logically necessary. If that were so, how would it follow that God’s (necessary) existence somehow explains the (necessary) existence of objective moral values?

A bit later in his response to commentators, Craig offers some clarification on the concept of a “moral value.” Regarding the metaethical position I call moral anti-reductionism (which Craig calls ‘atheistic moral Platonism’ but is far better known by the horrible label ‘non-naturalism’), Craig writes this:

First, it is difficult even to comprehend the Platonist view. What does it mean to say, for example, that the moral value Justice just exists? It is hard to know what to make of this. It is clear what is meant when it is said that a person is just; but is bewildering when it is said that, in the absence of any people, Justice itself exists. Moral values seem to exist as properties of persons, not as mere abstractions – or at any rate, it is hard to know what it is for a moral value to exist as a mere abstraction. (169, italics in last sentence mine)

Craig’s selection of “justice” as his example of a moral value is odd. Craig is aware of the distinction between moral values and moral duties; indeed, he emphasizes it in his writings. But most definitions of “justice” introduce the concept of law through the back door. For example, the Internet Encyclopedia of Philosophy begins its article on justice with the words:

Justice is one of the most important moral and political concepts.  The word comes from the Latin jus, meaning right or law.  The Oxford English Dictionary defines the “just” person as one who typically “does what is morally right” and is disposed to “giving everyone his or her due,” offering the word “fair” as a synonym. (LINK)

In this context, “law” and “right” (including “morally right”) are deontological (duty) concepts, not axiological (value) concepts. This muddies the waters; if we say that “justice” is a moral value, it seems to be a different animal from other moral values which don’t refer to deontological concepts in their very definition. Perhaps we might call “justice” a ‘second-order moral value,’ since it is a moral value which is conceptually dependent upon a deontological concept, and say that we want a first-order moral value, a value which doesn’t combine concepts. Fortunately, Craig provides other, neater examples: mercy, love, and forbearance (170).

Here I want to use moral values like mercy or love to show that God’s necessary existence is not a sufficient condition for explaining the necessary existence of moral values. If moral values like mercy or love “exist as properties of persons, not as mere abstractions,” it would seem that they are relational and so would require that two or more persons exist. But, even if we assume that (mere) theism is necessarily true, the proposition, “More than one person exists,” is a contingent proposition. Mere theism doesn’t entail Christian theism, which in turn means it does not entail the Christian doctrine of the trinity is true, and so it does not entail the existence of multiple divine persons. Furthermore, mere theism doesn’t entail the existence of any non-divine persons. So, even if it were the case that theism is necessarily true, it wouldn’t follow that more one person exists.

But if, “More than one person exists,” is a contingent proposition, this creates a problem for Divine Nature Theorists (DNT-ists) like Craig who want to argue that God’s nature explains all objective moral values, including relational moral values like love and mercy. Sure, there is a sense in which we can talk about a person loving themselves or having mercy on themselves, but I think it’s clear that not what people usually have in mind when they talk about “love” and “mercy” as moral values. (Besides, it’s hard to imagine how or why God would have “mercy” on Himself.) So if moral values are properties of persons; if some moral values are relational; and if “More than one person exists” is a contingent proposition, then there are possible worlds in which God exists but relational moral values do not exist. Thus, God’s existence, even God’s necessary existence, cannot explain necessary truths about all objective moral values because it cannot explain necessary truths about relational moral values. But that entails Craig’s moral argument fails.