In an earlier post I argued that the nature of science is such that it cannot demonstrate an entity/event to be uncaused, and thus scientific discoveries can never inveigh against the causal premise (“whatever begins to exist has a cause”) of the kalam cosmological argument (KCA) for God’s existence. Here I want to extend the discussion to the cosmological premise (“the universe began to exist”) of the KCA as well.
The contrapositive of the second premise is “the universe is eternal.” The nature of science, however, renders it incapable of demonstrating the universe to be eternal even if the universe were eternal. Why? 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.
To see why, 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 findings can support the premises of the KCA, they cannot rebut the same.