William Lane Craig has build a huge case for the existence of God based on it. The argument is:
(1) Whatever begins to exist has a cause for its coming into being.
(2) The universe began to exist.
(3) Therefore, the universe has a cause for its coming into being.
Craig needs to shore up the minor. He thinks it can be proven by reason alone. His main argument is that you cannot traverse an actual infinite. If the universe had no beginning, than an infinite number of days or seconds must have elapsed in order to arrive at the present moment. And this is impossible. Hence the universe had a beginning.
Unfortunately for Craig, the situation is not as if there was a moment in time at which the universe began which is infinitely far away from the present moment. If there was such a moment, then indeed it would take an actually infinite number of days to get from it to the present moment. But there was no such moment! According to the objector, the universe never began to exist; hence there is no moment at which it did begin to exist which just happens to lie at an infinite distance from today in terms of time. St. Thomas counters in a coup de grace in (ST, I, 46, 2, reply 6) that “Passage is always understood as being from term to term. Whatever bygone day we choose, from it to the present day there is a finite number of days which can be passed through.”
In this way there is no actual infinite but only a potential infinite, such that no matter how deeply we regress into the past, the distance between that point and now is finite. But that is not sufficient for kalam which is supposed to be natural and not revealed theology.
Look, the point is simple. I ask Craig, in order to accumulate the actual infinite, from what are we counting forward? I submit he can’t answer this quesion, and therefore, no actual infinite can be built. He can’t say “from -∞,” because that symbol can indeed mean “actual infinity,” which begs the question. I mean, -∞ is not a date.
The only way out for Craig in light of this argument is to assert that infinite past is unintelligible. But this escape was destroyed in the previous post.
In short, if atheists see the sort of arguments Craig and Copan use to prove God’s existence, they’ll laugh at them and be perfectly justified in so doing.