It continually surprises me that the Kalam Cosmological Argument (which, I believe, may be the single best proof for God’s existence that natural theology can offer) is rebutted with such brevity that one would conclude that the argument must be a particularly miserable one. Yet, the brief responses, I believe, are more indicative of a lack of good objections than they are of the Kalam argument’s inadequacies. The late John Mackie, perhaps one of the most influential atheists of recent times, offers just such a critique in his book, The Miracle of Theism.
In Mackie’s treatment of the arguments against the existence of an actual infinite in the real world he addresses two supposed problems- that it is impossible to traverse an infinite amount of time to the present time, and the objection expressed by al Ghazali, that in actual infinities a part of a set can be equal to the whole. But that’s it. To my bafflement, Mackie doesn’t even mention Hilbert’s Hotel, Craig’s Library, or Russel’s Tristram Shandy paradox! That such a meager effort leads to his claim “In short, it seems impossible to disprove, a priori, the possibility of an infinite past time.”  is practically a travesty. In short indeed. Too short.
However, these considerations are mostly irrelevant, since Mackie grants that scientific evidence lends credibility to the claim that the past is finite. That brings us to al Ghazali’s ‘crucial assumption’:
“[We] know by rational necessity that nothing which originates in time originates by itself, and that, therefore, it needs a creator.” 
Mackie is skeptical of this claim, charging that “Surely the assumption required here is just the same as that which is used differently in the first cause argument, that anything other than a god needs a cause or a creator to depend on it.”  But how exactly are these claims identical? Ghazali’s claim is compatible with the claim that the universe has existed eternally and thus does not require a creator. The claims are not the same.
In fact, as Mackie well knows, the Kalam Cosmological Argument can be formed without even mentioning God or a Creator. As Craig formulates it:
1. Everything which begins to exist has a cause.
2. The universe began to exist.
3. Therefore, the universe has a cause.
The Kalam argument thus only establishes a cause of the universe. Further philosophical analysis is needed in order to demonstrate that the cause is in fact a personal Creator. Thus, contra Mackie, the Kalam Cosmological Argument does not rely on the concept of a necessary being, nor does it rely on special pleading for God’s lack of need of a cause.
Also note that al Ghazali’s claim is very strong; he contends that rational necessity compels us to accept a cause of the universe (provided the universe had a beginning). Yet, in order to be a good argument, the Kalam need not carry this burden. For, as long as the 1st premise of the CA is more plausible than its negation, then the argument is successful. Of course, Martin doesn’t even attempt to demonstrate this- as most skeptics of the CA, he merely staves off the inference to a cause by claiming that “We have no good ground for an a priori certainty that there could not have been a sheer unexplained beginning of things.”  As I have argued, Mackie’s claim that we cannot have a priori certainty of this premise does little to show that it is more rational to believe in its negation.
Despite this, I think it is possible for us to have either a priori or a posteriori certainty that things which begin to exist have a cause. We intuitively recognize that effects require causes in the everyday world. When we hear a thud in the basement, we instantly and unwaveringly assume that the thud was caused. One may even say that we are certain that such is the case. As a metaphysical principle, the claim that all events that have beginnings have causes is indeed compelling, perhaps to the point of certitude. 1
Last of all, Mackie attempts to cast doubt on the explanatory power of theism. First he claims,
“…there is a priori no good reason why a sheer origination of things, not determined by anything, should be unacceptable, whereas the existence of a god with the power to create something out of nothing is acceptable.” 
Although creatio ex nihilo is admittedly baffling, there is indeed a simple and intuitive reason to regard it as rationally preferable to a sheer origination of things. Whereas creatio ex nihilo lacks a material cause, a sheer origination of things lacks both a material cause and an efficient cause. Any sorts of problems that one may conjure up with regards to God’s creation of the universe will apply to the hypothesis of sheer origination, and the hypothesis of sheer origination will still remain much more implausible since it also denies an efficient cause of the universe. Thus, it is impossible for a sheer origination to be as plausible as God’s creative act, much less more plausible.
Mackie notes (rightly, in my view) that God must not exist in time (at least sans the universe 2). In fact, I would actually argue that this is the positive and desirable conclusion one reaches by an analysis of the cause of the universe. This view is problematic, in Mackie’s view, because it “would be a complete mystery.”  Even if Mackie is correct here, why should we assume that such a “complete mystery” undermines the Kalam argument? After all, a sheer origination of things (which lacks a material and efficient cause) seems much more mysterious. It still seems that, like it or not, God’s creation of the universe is the most plausible and coherent view in light of a beginning of the universe. Yet, notice that Mackie gives no defense of the claim that timeless existence is a complete mystery. Philosophers regularly consider entities which they sometimes consider to exist timelessly, such as abstract objects or moral statements. Although it may be difficult to truly perceive of a timeless being, this does not demonstrate that it is rationally unbelievable.
In the end, Mackie essentially claims that it is impossible for us to rationally believe that God caused the universe. He states, “But in so far as we find [a sheer origination of things] improbable, it should cast doubt on the interpretation of the big bang as an absolute beginning of the material universe; rather, we should infer that it must have had some physical antecedents, even if the big bang has to be taken as a discontinuity so radical that we cannot explain it, because we can find no laws which we can extrapolate backwards through this discontinuity.” [94-95]
It seems that Mackie is saying that we should prefer a naturalistic precedent to the big bang no matter what the evidence. I can hardly see why we should prefer such a thing. If atheism must support itself by adopting counterintuitive or physically unintelligible/improbable models of the origination of the universe just to remain rationally acceptable, then it hardly seems to be the preferable worldview. Mackie’s atheism is unfalsifiable- to the extent in which physical models of reality undermine atheism, to that extent they should be considered false or incomplete.
But what is he even talking about here? What physical antecedents could there be, in theory? Perhaps he is referring to oscillating models, which have been overwhelmingly refuted by physical evidence from cosmology and hence almost entirely abandoned. 3 Surely Mackie must at least attempt to provide some explanation of what he means. His “explanation” is no such thing.
Furthermore, notice that Mackie’s argument here depends upon the failure of arguments against an actual infinite. Obviously, if Mackie wants to avoid the inference to theism by way of physical antecedents to the Big Bang, he must either assume an infinite regress of causes or else assume that, somewhere down the line, some ground of reality (whether it be an alternate universe or whatever) exist eternally. Yet, both of these possibilities involve an actual infinite in the world. So, if it is impossible for an actual infinite to exist in the world, then it is impossible (not merely unlikely) for Mackie’s atheistic interpretation of the universe’s origin to hold water. But, as we have already seen, Mackie does not even address, let alone refute, any of the multitude of arguments against an actual infinite advanced by philosophers today. So it may turn out that Mackie’s interpretation is simply untenable.
I think that the inadequacy of Mackie’s objections to the Kalam Cosmological Argument is patent. Essentially, he makes three charges:
1. We have no good grounds for a priori assuming that a sheer origination of things is impossible.
2. Theism lacks explanatory power.
3. We are more rational to assume that the Big Bang had an antecedent cause.
However, (1) does not even undercut the Kalam, even if true. (2) is completely unsupported by Mackie, and fails to take into account that, while Creation ex nihilo may be difficult to conceive, a sheer origination has all the problems Creation has, as well as additional absurdities (namely, denying an efficient cause for the universe.) Finally, (3) is false and only establishes Mackie’s blind faith commitment to naturalism and, moreover, does not really address arguments against actual infinities.
NOTE: After writing this article, I discovered that Craig actually already has a response to Mackie on the Internet. 4 The article here raises many of the same points, although I will happily submit that Craig’s is much more erudite and well-written. In addition to the objections I provide, Craig also defends the two arguments against the infinite that Mackie objects to.
1. Attempts to offer empirical counterexamples, such as the appearance of virtual particles by quantum vacuum fluctuations are misleading because the “vacuum” in which these events takes place is actually a sea of continually fluctuating energy, not “nothing.” See Part C of my article Here.
2. Although I will admit to be inadequately researched in God’s relationship to time, I am somewhat persuaded by Craig’s conclusion that God exists timelessly without the universe and temporally with it. See his articles on divine eternity here.
4. Craig, William Lane. “Professor Mackie and the Kalam Cosmological Argument.” Religious Studies 20 (1985): 367-375. Available at http://www.leaderu.com/offices/billcraig/docs/mackie.html