3 But even although we should be under the necessity of accepting the exegesis advocated by some—for the subject is not altogether unworthy of notice—and of saying thus, that He has actually blinded the minds of them that believe not, we should still have to affirm that He has blinded them for good, in order that they may recover their sight to behold things that are holy. For it is not said that He has blinded their soul, but only that He has blinded the minds of them that believe not.
And that mode of expression means something like this: Blind the whorish mind of the whore-monger, and the man is saved; blind the rapacious and thievish mind of the thief and the man is saved. But do you decline to understand the sentence thus? Well, there is still another interpretation. For the sun blinds those who have bad sight; and those who have watery eyes are also blinded when they are smitten by the light: not, however, because it is of the nature of the sun to blind, but because the eye's own constitution is not one of correct vision.
And in like manner, those whose hearts are afflicted with the ailment of unbelief are not capable of looking upon the rays of the glory of the Godhead. And again, it is not said, “He has blinded their minds lest they should hear the Gospel” but rather “lest the light of the glory of the Gospel of our Lord Jesus Christ should shine unto them.” For to hear the Gospel is a thing committed to all; but the glory of the Gospel of Christ is imparted only to the sincere and genuine.
For this reason the Lord spoke in parables to those who were incapable of hearing, but to His disciples He explained these parables in private. For the illumination of the glory is for those who have been enlightened, while the blinding is for them who believe not. These mysteries, which the Church now declares to you who are transferred from the lists of the catechumens, it is not her custom to declare to the Gentiles. For we do not declare the mysteries touching the Father, and the Son, and the Holy Spirit to a Gentile; neither do we speak of the mysteries plainly in presence of the catechumens; but many a time we express ourselves in an occult manner, so that the faithful who have intelligence may apprehend the truths referred to, while those who have not that intelligence may receive no hurt.
Source: Acts of the Disputation with the Heresiarch Manes (New Advent)