The rationalist is always downstream of the poet. Right brain can contain left brain, but not vise versa. That's why we can't logically prove the existence of God, and tie it up in a neat little bow like the theory of relativity. Proof will always be probabilistic, not demonstrative.
St. Thomas Aquinas understood this. Although he said proofs can be demonstrative for believers, because they already took the leap of faith. This is the whole point. God requires each of us to work for it: to find our own path towards salvation and liberation, to make belief and faith our own, and to discover Truth in our minds and hearts. We would never value anything that was easily provable anyway.
I spent the last couple weeks taking an abridged class on the St. Thomas and the Philosophy of God. I've always felt I've leapfrogged over some essential philosophy by taking on the modernists and postmodernists first. I realize now many of the errors from modern philosophy resulted in its disdain for tradition.
Much of modern philosophy assigns greater reality to the parts of an organized whole than to the whole itself, while the postmodernism maintains that the only the parts have reality and that the wholes they constitute are illusory. Aquinas started with metaphysics as the study of being knowing that Truth could be found in a natural reason that was in service to what was above reason. Reason and logic can only prove tautologies; so we start with existence to prove what exists antecedent to it. Simple (or maybe not).
One of the most fundamental distinctions in traditional philosophy is that between act and potency. This is just a more fancy way to make the distinction between permanence and change, or necessity and contingency. But for something to change sans chaos, there must be something that stays the same. As such, the ultimate cause of all change does not change. And that is ultimate act, or God.
Since the ultimate act is perfect (not lacking excellence), God is perfect in intelligibility, love, beauty, truth, goodness, and so on. The big insight that went along with this is that potency is always correlative with the act, so God being the ultimate act of intelligibility gives man faith in reason to discover creation.
Not everyone prefers this version of God. For one, it comes off as God is outside the whole order of creation, and man is ordered to Him, and not conversely. Therefore, there is no dynamic relationship between God and the world. This is sometimes viewed as a sort of deism, where God creates all at once and then does not engage in creation. This isn't exactly the nuance Aquinas was pointing towards. He says, “It ought to be said that the gifts of grace are added to nature in such a way that they do not take away nature but perfect it; whence the light of faith, which is instilled in us by grace, does not destroy the light of natural reason, instilled in us by God.” Grace (or the Holy Spirit) is the mediator between God and man, but in the vertical over the horizontal.
In regards to the spiritual modernists who want to immanentize and depersonalize God (via process theology or evolutionary panentheism), Chesterton makes a clever quip in his book about St. Thomas: “By their superficial theory everything can change; everything can improve, even the nature of improvement. But in their submerged common sense, they do not really think that an ideal of kindness could change to an ideal of cruelty. It is typical of them that they will sometimes rather timidly use the word Purpose; but blush at the very mention of the word Person.”
He then later concludes, “the essence of the Thomist common sense is that two agencies are at work, reality and the recognition of reality; and their meeting is a sort of marriage. Indeed it is very truly a marriage, because it is fruitful; the only philosophy now in the world that really is fruitful. It produces practical results, precisely because it is the combination of an adventurous mind and a strange fact.”
Very strange indeed.