Iucunda Sane §18

¹⁸ Meanwhile, however, it is painful to have to apply to men not lacking in acumen and application the rebuke addressed by St. Paul to those who fail to rise from earthly things to the things that are invisible: "They became vain in their thoughts and their foolish heart was darkened; for professing themselves to be wise they became fools" ( Rom . i. 21, 22). And surely foolish is the only name for him who consumes all his intellectual forces in building upon sand.