But what is a theologian good for? We can answer this question by looking at the church father Augustine. Augustine was faced with a deep and serious theological problem: Before today, there was yesterday, and before yesterday, there was the day before yesterday, and so on. But how can this be? Does the series of yesterdays extend infinitely into the past? If so, then how could God have created a universe that has always existed? If not, there must have been a beginning, but what had been going on before that? If the universe was created by God, then what was God doing before He created the universe?
To these questions Augustine gave an astounding answer that does not seem to have occurred to anyone before him: God created time along with the universe. In other words, “before” the universe there was no time. The universe is like a series, which may or may not extend infinitely backward and forward in time. But God stands outside the series, and this is what we mean when we say God is “eternal.” Eternal does not mean “goes on forever”; it means “stands outside of time:’ Notice that Augustine was not engaging in vague theological speculation. He was making a radically counterintuitive claim about the nature of physical reality. Today we know from modern physics and astronomy thatAugustine was correct; time is a property of our universe, and time came into existence with the universe itself. Augustine’s reflections on the nature of time, which were generated entirely through theological reasoning, are some of the most penetrating insights in the history of thought.
In order to get a sense of how Christians reasoned about God, I’d like to consider two famous arguments for the existence of God and match the wits of ancient Christian thinkers against those of their modern atheist detractors. The first is Aquinas’s argument based on causation. Aquinas argues that every effect requires a cause, and that nothing in the world is the cause of its own existence. Whenever you encounter A, it has to be caused by some other B. But then B has to be accounted for, so let us say it is caused by C. This tracing of causes, Aquinas says, cannot continue indefinitely, because if it did, then nothing would have come into existence. Therefore there must be an original cause responsible for the chain of causation in the first place. To this first cause we give the name God.
