Our Lord Jesus Christ wanted the things he did bodily also to be understood spiritually. He didn’t perform wonders for their own sake but so that the things he did would seem wondrous to those who saw them but would be known for their truth by those who understood them. It’s like when someone who can’t read sees the lettering in a well-written book; he admires the beauty of the letters and praises the skill of the copyist, but he doesn’t know what the letters mean: he praises what his eyes see but his mind doesn’t grasp. Someone else, however, both praises the art and grasps the meaning. ... So those who saw Christ’s wonders and didn’t understand what they mean and what in some way they intimate to those who do understand wondered that they were performed, while others both wondered that they were done and understood their meaning. That’s the sort of persons we too should be in Christ’s school.  (Sermon 98, 3; PL 38, 592)