This is the weekly Q & A blog post by our Research Professor in Philosophy, Dr. William Lane Craig.

Question

Hi Dr. Craig,

For about the last decade I've studied the question of the existence of God. I was raised in a Christian family and became interested philosophically in the existence of God in my mid-teens. I have read several of you books and many articles, as well as watching numerous lectures and debates. I have considerable respect for you work, mainly because it is meticulous - in contrast to most discussion of the subject that is readily available on the internet. I regard your defence of the kalam argument to be one of the best defences of God's existence I have read. I would describe myself as a 'philosophical theist.'

Preamble to my question:

In my reading of the history of natural theology, I've come to notice that many of the best defences of God's existence are made in the context of robust metaphysical systems. To give a few examples: Plotinus' argument for 'the One' in the Enneads, Aquinas' Five Ways (which must be understood within the context of Scholastic metaphysics), Leibniz's cosmological argument (which can only be understood properly within the context of rationalist metaphysics).

By contrast, your defence of the existence of God seems to be all over the place, metaphysically. The kalam argument makes several distinctions that are clearly rooted in Aristotle, e.g., the distinction between potential and actual infinite series, which is clearly rooted in Aristotle's distinction between 'being in act' and 'being in potency' and your occasional distinction between 'material' and 'efficient' causes, which is clearly rooted in Aristotle's Four Causes. However, you also defend the Leibnizian contingency argument, which is based in the rationalists' understanding of the distinction between 'necessary' and 'continent' existence (which is distinct from the way in which the Aristotelians use these terms). Again, the 'fine tuning' argument presupposes a mechanistic view of nature, seemingly incompatible with an Aristotelian conception of nature (which is intrinsically teleological). You also defend Plantinga's ontological argument, which presupposes something like a David Lewis' 'possible worlds' modal metaphysics.

My question:

I would presume, considering your expertise, that you are aware of the different metaphysical systems underpinning your different arguments. How do you reconcile these differences, if at all? What is your metaphysical system? Do you think that it is wise to defend arguments with such different and seemingly incompatible metaphysical assumptions? Doesn't this just make your case for the existence of God more incoherent?

I ask this last question, because it seems to me that many atheists frequently misrepresent theistic arguments, and the biggest problem (I suspect) is ignorance of the metaphysical underpinnings of these arguments.

Isaac

Australia

Dr. William Lane Craig’s Response

Dr. William Lane Craig

This is a very perceptive question, Isaac, one which I confronted very early on in my thinking about natural theology but which no one has ever thought to ask me before.

My initial training in philosophy of religion was under Norman Geisler, who follows the philosophy of Thomas Aquinas. It worried me that in order to accept Thomas’ main argument for God’s existence, one had to first embrace the Aristotelian-Thomist metaphysic underlying it, for example, the so-called real distinction between essence and existence. That seemed (and seems) to me to make the argument unusually vulnerable. Just reject the controversial metaphysic underlying the argument, and the argument becomes nugatory!

It was then that I determined to craft arguments for God’s existence that were not system-dependent upon a particular metaphysic but could be accepted by people of varying metaphysical outlooks. That broadens the appeal of the arguments and makes them more immune to refutation.

So, for example, the twin premises of the kalām cosmological argument are so simple and relatively free of deep metaphysical commitments that they are widely acceptable to people of divergent viewpoints. Now, of course, the argument does make use of various metaphysical concepts, as you note. But one can accept, for example, Aristotle’s intuitive distinction between an efficient cause and a material cause without buying into full-blown Aristotelian metaphysics. This helpful distinction crosses metaphysical lines. Similarly, the distinction between actual and potential infinites has passed into standard mathematics, where it is wholly independent of an Aristotelian metaphysics. Probably the biggest metaphysical assumption made by the kalām cosmological argument as I develop it, which I did not at first appreciate, is its commitment to the objectivity of temporal becoming. But again, that commitment is hardly unique to any metaphysical system and can be defended without espousing some such system.

Similarly, with respect to the Leibnizian cosmological argument, one need not embrace a rationalist metaphysics (not to speak of Leibniz’s monadology!) in order to accept a modest version of the Principle of Sufficient Reason, such as features in the version of the argument I have defended. True, the distinction between “necessary” and “contingent” in this argument is not Aristotelian; but the Leibnizian understanding of these terms is the understanding that has become the standard view in contemporary analytic philosophy. So I’m using these words with the customarily accepted meanings.

As for fine-tuning, I don’t think it presupposes a non-teleological view of nature; that is to say, it doesn’t presuppose that things do not have ends toward which they tend. Rather the argument makes no assumption in that regard (and thus is free of controversial Aristotelian assumptions, get it?) and so has force not only for those who believe in final causes but also for those who don’t.

As for the ontological argument, it most certainly does not presuppose anything like Lewis’ modal realism, according to which possible worlds are other concrete, spatio-temporal universes! It doesn’t even presuppose that possible worlds are maximal states of affairs, as Plantinga used to think before his conversion to divine conceptualism regarding putative abstract objects. The argument is perfectly compatible even with an anti-realist view, according to which possible worlds are just a heuristic device akin to mathematical diagrams.

So in answer to your question: I deny that there are “different metaphysical systems underpinning your different arguments.” The arguments, while drawing upon metaphysical concepts and insights which appear in various systems (concepts and insights many of which have become generally or at least widely accepted), are independent of those systems in which these concepts may have been initially enunciated. So there’s no need to “reconcile these differences.” Do I “think that it is wise to defend arguments with such different and seemingly incompatible metaphysical assumptions?” No, but the arguments I defend are characterized, quite deliberately, so as to be as free as possible from extraordinary metaphysical assumptions, not to speak of seemingly incompatible assumptions, so as to broaden their appeal as much as possible. The premises of the various arguments are perfectly coherent, and no one I’m aware of has argued otherwise.

Finally, “What is your metaphysical system?” This question made me smile. I guess I don’t have one! I mean, I’m a theist, a tensed time theorist, a Divine Command theorist, a substance dualist, an anti-realist about abstract objects, and, I suppose, many other things. But I don’t have any sort of system other than the composite of these various commitments. In any case, my natural theology aspires to be as system-free as possible in order to appeal as widely as possible to people of different persuasions.

This post and other resources are available on Dr. William Lane Craig's website: www.reasonablefaith.org

Learn more about Dr. Craig’s book, A Reasonable Response.