Philosophia ancilla theologiae.

From "On Canons:"

...

Most textbooks in the history of philosophy follow what might be called the Sleeping Beauty narrative: Philosophy thrived on its own from the pre-Socratics to Plotinus, at which point the Christian Church intervened with a faith-based philosophy (a contradiction in terms in this telling), at which point philosophy went to sleep until awakened by the Frog Prince Descartes, who kissed the slumbering Lady Philosophy awake with his method of radical doubt, hauling the entire scholastic past before the bar of reason, leaving it in tatters and philosophy finally liberated.

Gilson, however, retorted that, far from poisoning philosophy with a sleeping potion, faith illuminates from above the path reason would follow in any event if it only had a map and a flashlight. Philosophy’s goal has always been the truth, but it has to grope because it can’t see that far ahead. To understand Gilson’s thesis, think of it this way: When one is first studying algebra, say, especially when using one of those teach-yourself books, the problems are given in the front to work out on one’s own, with the answers keyed at the back. Now, if one works out a problem only to discover from the answer key that one got it wrong, one knows then and there that one was wrong but not how or why. For that one needs to go back and retrace one’s steps and see how one can rationally prove both the false step and the true path.

Similarly in philosophy, a Christian already knows on the basis of revelation that materialism is wrong, which means that any philosopher arguing for materialism must have made a wrong step, or more probably several, somewhere along the line. But that fact alone is not enough to refute materialism. One must then put oneself in the shoes of the materialist and walk through his arguments with him and point out his errors by the rules of rational thought and not by revelation.

...

Of course, in viewing philosophy as ancilla theologiae we do not relegate it to a strictly submissive or functional role with respect to theology. Rather, we reaffirm the "necessity of the link between the two sciences and the impossibility of their separation" (see Fides et Ratio).

To use the Maritainian metaphor, the nature of theology is that of guidepost to philosophy; theology illuminates to philosophy paths to follow and potholes to avoid, but it is still up to philosophy to judge its own conclusions based on the rationality of its arguments. The benefit of such a situation is that philosophy is thereby more apt to pursue answers to "higher" questions (questions of a metaphysical nature), rather than be bogged down by the unavoidable (and ultimately pointless) infinite-regression loops associated with postmodernism and decontruction that are, somehow, still all the rage.

["On Canons"]