There is a paradox in the notion of ultimate goods. They set our goals and measure our actions, so we need to align ourselves with them if our life is to hang together. However, we can’t define what they are without diminishing them. To state them fully would be to subordinate them to what defines them and demonstrates their goodness, and so to deny that they are ultimate.
We can’t do without ultimate goods, but we can’t really grasp them either. It is that situation that makes faith, humility, and consciousness of sin the necessary human condition, at least in a society that is complex enough for there to be serious moral indeterminacy and conflict. We are obligated to act in accordance with certain goods that we cannot fully identify. We can therefore only act in faith, and in fear and trembling.
Nonetheless, the faith must have some positive content to do us any good at all. But how can the “evidence of things unseen” have positive content that is concrete enough to use? And how can that content go beyond the propositional, since propositions are too limited for ultimate things? Catholic Christianity—faith in God become man and still present among us through a visible authoritative Church—is intended as a solution to the problem. It is hard to think of any other that could work.