CCC § 50: By natural reason man can know God with certainty, on the basis of his works. But there is another order of knowledge, which man cannot possibly arrive at by his own powers: the order of divine Revelation.I think faith and intellect are the coolest two gifts could have given man. I'm not sure what else he could have given us, but still.
Faith and reason complement each other as they both originate in God, and man is gifted with these in our spiritual and rational souls. In simple terms, reason is our ability to think and process, even somewhat passively (I think it is combined with what we often call intuition). As the passage tells us, man can only know so much because he is limited in comprehension to what is physically made known in the world. That's a lot, actually. It allows to us to find Truth, namely the Creator (using logic), and and his order (the natural/moral law).
From the Catholic Encyclopedia:
Objectively, it [faith] stands for the sum of truths revealed by God in Scripture and tradition and which the Church presents to us in a brief form in her creeds, subjectively, faith stands for the habit or virtue by which we assent to those truths.Faith and reason are inseparable; Blessed John Paul II wrote an encyclical letter on this point in 1998 entitled (you guessed it!) Fides et Ratio, or 'On Faith and Reason.'
It's a toughie to wrap your head around. As I'm writing this, I am struggling to get it. I think that's a good thing, for faith, and consequently everything that stems from it like salvation, is not an act of the will, but a gift of God. Funny how I don't remember that much of the time, considering that my name means 'gift from God.'