There is no part of scripture, I mean to say, which it is not the easiest thing in the world to find fault with, to the dismay of those who do not understand it. But that is precisely why divine providence permits so many heretics to come along with various errors; it's so that when they taunt us and shower us with questions we do not know the answers to, we may at least in this way be shaken out of our mental sloth and start longing to become acquainted with the divine scriptures.
That is why the apostle too says: "There have to be many heresies, so that those who prove reliable may stand out among you" (1 Cor 11:19). Those who can teach well are the ones who prove reliable in God's eyes. But they can only stand out among people when they teach; and they are unwilling to teach those who do not want to be taught. But many people are lazy to want to be taught, unless they are sort of awakened from their slumbers by heretics making a nuisance of themselves with their taunts, so that then they start feeling ashamed of their ignorance, and begin to realize that they are being put in a dangerous position by this ignorance of theirs.
If they are people of sound faith, they do not give in to to the heretics, but earnestly seek inquiring what answer they can make to them. God, of course, does not abandon them; and so when they ask they receive, and when they seek they find, and when they knock the door is opened to them. Those on the other hand who despair of being able to find what they seek in Catholic teaching are practically rubbed out by errors of all sorts; and if they still, nonetheless, go on preserving with their inquiries, they eventually return, tired out and thirsty after enormous toil, and almost dead, to the very springs from which they strayed away.