(1) Anything that begins to exist requires a cause
(2) The universe began to exist
(3) Thus, the universe requires a cause
Additional logical inferences allow us to identify this cause as God. Whatever caused space, time, and matter to begin to exist cannot itself be spatial, temporal, or material. Furthermore, whatever caused our orderly, life-permitting universe to come into being a finite time ago must be immensely powerful, intelligent, conscious, and hence personal. These are apt descriptions of a being theists have long identified as God.
Both premises have been challenged on scientific grounds. Premise one is typically challenged on the basis of quantum mechanics, while premise two is challenged by new cosmological models that seek to restore an eternal universe. I am going to argue that neither premise of the argument can be undermined by scientific evidence, and thus the argument itself is impervious to scientific refutation. Only philosophical arguments are capable of undermining either premise of the argument.
Some seek to undermine this causal argument for God’s existence by denying the first premise. They point to quantum mechanics and virtual particles as evidence that there are exceptions to the causal principle.
In regards to quantum mechanics, an appeal is made to Heisenberg’s Indeterminacy Principle which holds that one cannot accurately determine with precision both the position and momentum of an electron simultaneously. If you measure its momentum, its position changes; if you measure its position, its momentum changes. This makes it impossible to accurately predict the future motion of an electron. While this is a physically accurate description of what we observe on the quantum level, some have improperly understood this to mean that the momentum of electrons is uncaused. This is an unjustified use of science. Heisenberg’s principle pertains to predictability (of the location and momentum of subatomic particles), not causality. “The mere fact that we can’t predict something doesn’t mean that something has no cause.”
Many appeal to virtual particles as evidence of uncaused entities. Heisenberg’s Indeterminacy Principle allows for pairs of virtual particles to come into existence within the quantum vacuum for a fleeting moment before being subsumed back into the vacuum. It is said that these particles coming into being without a cause.
This conclusion is unjustified given the evidence. While we may not observe the cause, that does not mean there is no cause. Absence of evidence is not evidence of absence. Given our uniform experience of cause and effect, it is more likely to conclude that a cause exists that we have yet to detect than it is to conclude there is no cause. Indeed, the best explanation may be that virtual particles are caused by the quantum vacuum from which they originate.
For some, such explanations will not be sufficient. Until a cause for particle pair production can be observed or detected, they will maintain that it is more reasonable to conclude that such events are uncaused. This brings me to what I consider the ultimate rebuttal to scientific challenges to the first premise: science cannot, in principle, ever identify an uncaused effect, and thus it is never reasonable to conclude on the basis of science that something exists for which there is no cause. Let me explain.
Science contributes to our knowledge of reality by making observations about physical things. If they are able to directly or indirectly observe some X, then we have good grounds for adding X to our ontology. For example, when scientists detect a new particle such as the neutrino, we add neutrinos to our list of things that exist. While science can identify what exists by what it observes, science cannot identify what does not exist by what it fails to observe. If science cannot identify what does not exist by what it fails to observe, then the failure to observe a cause for particle pair production does not entail the absence of a cause.
Imagine for a moment that a scientist is barbequing some steaks in his backyard. While he is cooking, a piece of chicken suddenly appears on the grill. Strangely enough, it only appears for a brief moment before disappearing again. This happens multiple times. Quickly, the scientist grabs his instruments in hopes of detecting what is causing the chicken to appear on his grill. Despite all attempts to detect the cause, however, he finds nothing. Does this mean there is no cause? No, it just means he has failed to detect the presence of a cause. Perhaps the cause is too small or operates too quickly to be detected by his instruments. While he cannot rule out the possibility that the chicken’s appearance was uncaused, as a scientist he knows his failure to detect a cause is not proof that there is no cause. Absence of evidence for a causal entity is not evidence for the absence of a causal entity.
While the scientist can rightly claim he does not observe a cause for the chicken’s appearance on his grill, he cannot claim science has proven there is no cause. Likewise, while scientists do not detect a cause for the appearance of virtual particles in the vacuum, the absence of evidence for a cause is not itself evidence for the absence of a cause. It is beyond the scope of the scientific method to make conclusions about what does not exist. If there is such a thing as an uncaused entity, it would be impossible to identify it scientifically because science is based on observation and induction. It is impossible to observe the absence of something, and thus it is impossible to discover an uncaused entity by scientific methods. Scientific discoveries can never inveigh against the causal premise. If uncaused entities exist, they must be identified philosophically, not empirically/scientifically.
Premise 2 contends that the universe began to exist. Those seeking to undermine the second premise often point to various cosmological models involving an eternal universe. Whatever one might make of the mathematical merits of these models, the nature of science renders it incapable of ever demonstrating the universe to be eternal, even if the universe is eternal. Science is an empirical discipline based on what can be observed and quantified. For science to prove that the universe is eternal, it would have to do so empirically. But this is impossible. An eternal past cannot be observed or quantified.
Consider a staircase. Suppose there exists a staircase that extends far into space beyond what we are able to observe. Some speculate that the staircase is infinite in size, while others contend that it is enormous in size, but still finite. How would one go about testing whether the staircase was infinite or just really big? Remember, we are talking about science, so we are limited to empirical methods of inquiry. One way to test the possibility is for a scientist to start walking the staircase, counting each step along the way: one, two, three, four…1000…1,000,000…1,000,000,000…. Could our scientist conclude after traversing the 1,000,000,000th step that since the staircase continues on beyond his observational horizon it must go on infinitely? No. For all he knows, it may end 100,000 steps ahead, and if he keeps walking/counting for one more week he would finally reach the end of the staircase. Because he wants to make a scientific—and hence, empirical—assessment of the staircase’s size, our dedicated scientist keeps walking and counting. Could he, one hundred years and 100 trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion steps later, conclude that the staircase is infinite? No. For all he knows it could end one trillion steps from where he stands. So he traverses one trillion more steps, but there’s still no end in sight. Is he justified at this point in concluding that the staircase is infinite? No, not empirically. For all he knows, it could end one trillion steps from where he stands. Our scientists could go on counting for billions of years and traverse trillions upon trillions more steps, and he would always be in the same predicament: never able to know whether the staircase is truly infinite in size, or just a really really big (yet finite) staircase that he has yet to reach the top of.
The same is true of the universe. No matter how far back in time scientists are able to see by peering through a telescope, they can never know whether the universe continues on infinitely into the past, or just a little past their present observational horizon. Even if they could see 1 trillion years back in time, the empirical nature of science prohibits them from making any conclusions about what—if anything—is beyond that point. For all they know, the regress could keep going on forever, or it could terminate at 1.1 trillion years in the past.
Science can only speak to what it has observed, and since it is impossible to observe an infinite number of past moments, science is incapable of verifying that the universe has existed from eternity past. And if science is incapable of verifying that the universe is eternal, scientific objections against the second premise of the KCA are dead in the water. Only philosophy is equipped to answer questions about the existence of infinites. If it can be demonstrated philosophically that the infinite is incapable of being instantiated in reality, then it can be demonstrated that the universe is not past-eternal. While I think philosophy has demonstrated this quite clearly, even if I am mistaken and premise two is actually false, it could only be demonstrated to be so philosophically, not scientifically.
While scientific discoveries can support the premises of the KCA, they cannot inveigh against them.
Norman Geisler and Frank Turek, I Don’t Have Enough Faith to Be an Atheist (Wheaton, IL: Crossway Books, 2004), 87.