I recently read Augustine's The Trinity with some friends. I was once again struck by Augustine's rational theology. Edmund Hill, the editor, noted that Augustine did not distinguish between faith and reason. What? That is such a common distinction today or, as most moderns would like to think, a separation. For Augustine, reason was a subset of faith. In other words, every bit of our knowledge begins with faith in something that will lead us to knowledge.
In a debate on the existence of God (I recently watched on-line), atheist Richard Dawkins said his opponent had to rely on faith, whereas he proceeded according to reason alone. His insightful opponent responded by saying that Dawkin's position on God's non-existence also involved faith. When Dawkins insisted that his position was based on reason alone, his opponent asked him, "Well, don't you believe it?" Dawkins then back-peddled to try to answer on other terms.
I think it is inescapable that we must assume first principles that we cannot prove in a laboratory. The Christian believes that the Bible is a revelation from God and puts his faith in it. The Rationalist, on the other hand, assumes his reason as the starting point and basis of all knowledge. If the Rationalist wants to pretend that his approach is purely rational, it must be pointed out that it is an act of faith to trust in reason or any of our senses. I don't deny that reason should be trusted. I'm only pointing out that there is an element of trust, and that reason is trustworthy because it comes from God. Without God, the atheist has no ultimate basis for trusting in his reason or his five senses. He may say, "Well, they work." Yes they do, but why should they work if not given by God for unlocking the secrets of his created order? Reason itself is a mystery, especially if God does not exist.
Augustine held to the principle credo ut intelligam, or "I believe in order that I may understand." This means that we all must start with unproved presuppositions, if we are to understand anything. The only question is: "Are they the right presuppositions?" Our presuppositions can always be tested against the evidence as we go. If our presuppositions begin to block our understanding, then we can try new ones, like switching from the earth as the center of the solar system to the heliocentric solar system.
While Augustine, and the rest of us, start with faith or unproven assumptions, it is not the same as being irrational. I said earlier that I was impressed by Augustine's "rational theology." Indeed, as Calvin would later say, "Reason is a receptacle of revelation." Augustine does not use his reason to give rational proofs for the Trinity. The Trinity is beyond that. But he does give a rational account of the Trinity. In other words, he shows how the revelation of the Trinity makes sense and is not contrary to reason.
For instance, there is nothing irrational or contradictory about saying God is one in essence and three in person. But this doesn't dispel mystery either, for how can we have three persons who are God and yet avoid having three gods? All Augustine can suggest is that "person" is our best way speaking about the three-ness of God. When asked "three what?" all we can say is "three persons."
Augustine unapologetically appeals to revelation to avoid "tri-theism." He simply says that on the divine level, God's substance or nature is such that his persons constitute one being instead of three. C. S. Lewis in Mere Christianity says that on the creaturely level three persons equals three separate beings, but on the divine level it's different. God's divine nature is such that three persons are unified in one being. It's a mystery to us, but not an irrational one.
Hill sums up Augustine's approach well when he says: "Never is he [Augustine] so naive as to think he can 'prove' the mystery without recourse to faith." I hope that we as Christians won't be ashamed to call faith a virtue, and that Dawkins will be led to see that reason is a mystery that points to the one true God.