The Catechism of the Council of Trent

Such is the nature of the human mind and intelligence, that, although, by the application of great labour and diligence, it has of itself investigated and ascertained many other matters which appertain to the knowledge of divine things; yet, illumined by the light of nature, it never could have known or comprehended the greater part of those things, by which eternal salvation is attained, the principal end for which man was created and formed after the image and likeness of God.