3 To reply briefly to all these. To those who do not understand what is here set down, my answer is, that I am not to be blamed for their want of understanding. It is just as if they were anxious to see the new or the old moon, or some very obscure star, and I should point it out with my finger: if they had not sight enough to see even my finger, they would surely have no right to fly into a passion with me on that account. As for those who, even though they know and understand my directions, fail to penetrate the meaning of obscure passages in Scripture, they may stand for those who, in the case I have imagined, are just able to see my finger, but cannot see the stars at which it is pointed. And so both these classes had better give up blaming me, and pray instead that God would grant them the sight of their eyes. For though I can move my finger to point out an object, it is out of my power to open men's eyes that they may see either the fact that I am pointing, or the object at which I point.
Source: Christian Doctrine (New Advent)