An argument for God’s existence that has recently captured the attention of lay apologists and professional philosophers alike is the kalām cosmological argument. “Kalām” is the Arabic word for “speech,” and refers here to God, who “speaks” the world into existence. Though this argument is deceptively simple in its formulation, it has established itself as a formidable challenge even for sophisticated atheist thinkers.

In two parts, I’d like to introduce (or re-introduce) you to this important proof of God’s existence. Here in part I, we’ll consider the merits of the kalām argument. We’ll also consider a potential weakness. Finally, we’ll zero in on the first premise of the argument and reflect on its plausibility.

Part II will focus on the second premise and conclusion of the kalām argument. We’ll also consider some objections.

Here now are the premises and conclusion of the argument:

Premise 1. Everything that begins to exist has a cause of its existence.

Premise 2. The universe began to exist.

Conclusion. Therefore, the universe has a cause of its existence.

This argument is almost unmatched in its evangelical import. Besides its logical integrity, the greatest strength of the kalām cosmological argument is its elegance. It’s easy to memorize; it’s simple to articulate; and while uncomplicated on its face, it’s surprisingly difficult to refute. Every Christian should be familiar with it and be ready to use it when the occasion presents itself.

Yet one concern some raise is this: that the conclusion of the kalām argument does not prove enough. Some worry that, at most, it proves the God of deism—that is to say, a God who created the world but is no longer active in it as a sustaining, personal cause.

It may be argued that the conclusion of the kalām argument is not as “full-bodied” as other cosmological arguments, that it’s inferior to (say) the cosmological arguments from motion and contingency because it doesn’t entail a God who is actus purus, “pure act” (which is how St. Thomas Aquinas refers to God).

But before we pursue this concern much further, it would be prudent to ask a more preliminary question: What does it mean, anyway, to say that God is “pure act”?

This is important, so let’s take some time to consider this. First, in oversimplified terms, it just means that God is perfect in the greatest conceivable sense—that he is perfection itself, in fact. And this is consistent with the picture of God revealed by divine revelation (see, e.g., Ex. 3:14; Ps. 18:30; Matt. 5:48).

Here is a more technical way of getting at the same point. In philosophical terms, we could say that God is perfectly simple. He has no parts, neither physically nor metaphysically. Since our imagination is bound to three-dimensional picturing, you might find this very difficult to make sense of. But stick with me.

Since God is “simple” by his divine nature, nothing can be added to or subtracted from him in any way. He is the Creator of the universe (or multiverse, if you prefer) and is completely unbound by time, space, and all other existing physical constraints. Being infinitely perfect and unbound by time, then, we must also say that he is unchanging. This follows from the fact that time is, as St. Augustine tells us, the measure of change—but God, as we’ve said, is the creator of time.

Further, Augustine wrote that “there can be no time without creation,” from which it follows that anything prior to creation must be timeless. And if that thing is also absolutely perfect—as God is—then it must be more than merely timeless, or unbound by physical time (like the angels); it must be eternal. The sixth-century philosopher Boethius gives us a definition of what it means to be eternal: it is to be “in complete possession, all at once, of illimitable life.”

Here’s another angle on the same point. Since God is “pure act,” we might say that he does not have existence, but just is existence. You and I exist actually. But potentially we can always become more perfect (in some way) than we actually are. But God is—by nature—purely and actually perfect by virtue of the fact that he is purely and perfectly actual. And as such, God has no more potential to become more perfect than a perfect circle has potential to become more circular. Moreover, he can never become less than infinitely perfect because it is a mark of infinite perfection to be always infinitely perfect.

All of this entails what philosophers and theologians call “the doctrine of divine simplicity.” Conceived in this way, God can be defined as “that than which nothing greater can be thought” (as St. Anselm put it). To quote Eleonore Stump and Norman Kretzmann:

The short answer to the further question ‘Why is God simple?’ is ‘Because God is an absolutely perfect being, and absolute perfection entails absolute simplicity,’ and the fuller version of that answer is to be found in Christian rational theology as developed by Augustine, Anselm, and Aquinas, for instance.

Now this takes us back to the concern raised earlier about whether the kalām argument proves enough. Does it fail to prove a God whose nature corresponds to the doctrine of divine simplicity? At the very least, I think it must be admitted that it takes us a long way in the right direction.

Indeed, it might serve as a compelling lead-off argument, as part of a greater system of arguments which together form a whole “package” of convincing and converging probabilities (the sort of multi-tiered case for faith that St. John Henry Newman wrote about in An Essay in Aid of a Grammar of Assent). At a minimum, the kalām argument opens the mind toward the existence of a transcendent “first cause” of all physical reality and acts as a bridge to other related metaphysical demonstrations.

Returning to the argument now:

Premise 1. Everything that begins to exist has a cause of its existence.

Premise 2. The universe began to exist.

Conclusion. Therefore, the universe has a cause of its existence.

The first premise is also known to philosophers as the principle of causality. It states that if something begins to exist, it must have been caused to exist. Negatively, it implies the timeless maxim assumed by both ancients and moderns, that “out of nothing, nothing comes.” To deny this first premise is a bold move. As philosopher William Lane Craig contends:

To claim that something can come into being from nothing is worse than magic, when you think about it. When a magician pulls a rabbit out of a hat, at least you’ve got the magician—not to speak of the hat! But if you deny premise 1, you have got to say that the whole universe just appeared at some moment in the finite past for no reason whatsoever. But I do not think that any sane person sincerely believes that things . . . can just pop into being out of nothing without a cause.

If the principle of causality (i.e., first premise) were not true, then we would expect the world to be quite different than it is. We should expect that things would be “popping” into existence out of nothing all around us—or if not all around us, then at least here and there, from time to time. But we don’t experience such phenomena; nor do we expect such brutely uncaused events—not, at least, without forcibly rejecting our real-world instincts.

Moreover, imagine what a rejection of the causal principle would do to science? For there is hardly a more fundamental assumption made by scientists that, in nature, things which begin to exist have a cause (even probabilistic events like spontaneous quantum fluctuations depend on prior causal conditions and do not emerge from nothing, strictly speaking).

Further, when a phone bill shows up in the mail, or an anonymous gift shows up on our front porch unexpectedly, or an unknown truck is parked in our driveway, we never suppose that there is just no cause of their existence. We instinctually expect things that begin to exist to have a cause of their existence. We naturally assume this, just as we naturally hold other “common sense” beliefs for granted, like, say, that the world outside ourselves is real (and not a virtual simulation of some kind). We just don’t question such assumptions once we put our philosophy books down and re-assume what Edmund Husserl calls the “natural attitude” toward the world.

But also, we might think of the principle of causality as a “first principle” of rationality, for we always assume that our every thought has some grounding in prior truths. That is, when we think something is true, we typically think so because it logically follows from other thoughts that we hold to be in alignment with reality.

But if things can come into existence out of nothing, then surely our thoughts (or the brain events that ordinarily correspond with our thoughts) could come into existence without a cause. But such random, uncaused thoughts could hardly have any congruence to reality. Why? Because arising uncaused out of nothing, they would neither correspond with other truths nor with any neurological event—except by a random stroke of luck! Thus, as Alexander Pruss has pointed out, to allow for brute, uncaused events in reality may, in effect, undermine the reliability of our perceptions about the real world (including the thoughts we have about the kalām cosmological argument!).

All of this is not to say that the first premise cannot be challenged in ways that might even tempt the theist to reconsider his assumptions. To be sure, serious philosophers like Quentin Smith and Graham Oppy have offered interesting rejoinders. Though meriting our attention, such challenges remain highly controversial and in no way compel us to rebel against our intuitions and arguments in favor of the kalām argument’s initial premise.

At the end of the day, the first premise of the kalām cosmological argument is as true and verifiable as any premise could be. If there ever was an extraordinary claim that required extraordinary evidence, it would be this: that something can, and has, come into existence without a cause.