Aquinas' Five Ways (Intro)
Thomas Aquinas began by asking three questions:
1. Is it self-evident that there is a God?
2. Can it be made evident?
3. Is there a God?
Aquinas himself was convinced that the existence of God was not self-evident. You can't describe God the way you describe a tree or a mountain. You can't see, hear, smell, taste or touch God. He was also convinced, though, that the natural features of the world provide a great deal of evidence for God's existence.
In order to prove God's existence, Aquinas began with what people saw and experienced every day. Unlike Anselm, he did not believe that understanding the term "God" is enough to show that God exists. He rejected Anselm's a priori Platonic proof, which begins in the mind, and concentrated on five a posteriori Aristotelian proofs, which begin with the real world.
The awareness that God exists is not implanted in us by nature in any clear or specific way. Admittedly, man is aware of what by nature he desires, and he desires by nature a happiness which is to be found only in God. But this is not, simply speaking, awareness that there is a God, any more than to be aware of someone approaching is to be aware of Peter, even should it be Peter approaching. Many, in fact, belive the ultimate good which will make us happy to be riches, or pleasure, or some such thing.
In other words, God is not obvious.
So, Aquinas rejected Anselm's Platonism and thought it was impossible to climb from "truth" to "Truth" and call that Ultimate Truth "God".
There are some today who argue with the very existence of truth (never mind "Truth" or "Ultimate Truth"). Perhaps, if Aquinas lived today, the question he would wrestle with would be: If we can define neither truth, Truth nor Ultimate Truth, can the term "God" have any meaning at all?
In other words, in a world where truth has not merely gone out of fashion but is considered non-existent, how can one become convinced of the existence of God? And what kind of God would that be?