Many misunderstand the principle of invincible ignorance. It’s critics, both non-Catholics, and traditionalist Catholics, think that it is a recipe for universalism. In fact, invincible ignorance is a biblical principle that has been preserved by the Catholic Church down to this day. The following is an excerpt from a book I am writing with a friend, which details some of the biblical proof. As the Bible is readily available for public consumption, I have no qualms in presenting this section. The book also includes all the patristic proof that invincible ignorance has been preserved in the Catholic Church continuously down to this day, but due to possible copyright restrictions, I will not post the patristic proofs here (the book is being edited at this time):
The very notion of invincible ignorance has been in existence from the most ancient times. It is, first of all, very explicit from the pages of the Bible. In the Old Testament, there is a definite distinction made between acts committed in ignorance as opposed to those which are done in full knowledge. For instance:
If he touches human uncleanness, of whatever sort the uncleanness may be with which one becomes unclean, and it is hidden from him, when he comes to know it he shall be guilty. Or if any one utters with his lips a rash oath to do evil or to do good, any sort of rash oath that men swear, if it is hidden from him, when he comes to know it he shall in any of these be guilty. (Lev 5:3,4)
The fourth chapter of Leviticus is a record of the provisions made for sins done “unwittingly,” by priest, congregation, or ruler. Again, in Numbers, we have this distinction:
You shall have one law for him who does anything unwittingly, for him who is native among the people of Israel, and for the stranger who sojourns among them. But the person who does anything with a high hand, whether he is native or a sojourner, reviles the Lord, and that person shall be cut off from among his people. Because he has despised the word of the Lord, and has broken his commandment, that person shall be utterly cut off; his iniquity shall be upon him. (Num 15:29-31)
This passage expressively captures the very essence of the principle of invincible ignorance.
In the New Testament, Jesus himself tells the Pharisees, “If you were blind, you would have no guilt; but now that you say, ‘We see,’ your guilt remains” (Jn 9:39-41; see n.129 supra). And again, speaking to His Apostles, “If I had not come and spoken to them, they would not have sin; but now they have no excuse for their sin … If I had not done among them the works which no one else did, they would not have sin; but now they have seen and hated both me and my Father” (Jn 15:22, 24). St. Peter declares, “And now, brethren, I know that you acted in ignorance, as did also your rulers. But what God foretold by the mouths of all the prophets, that his Christ should suffer, he thus fulfilled. Repent, therefore, and turn again, that your sins may be blotted out, that the times of refreshing may come from the presence of the Lord”(Ac 3:17). Not knowing Christ is itself a sin worthy of condemnation, but here Peter excuses his audience because of their ignorance. But now that Christ has come, they should confess all their sins in the presence of the Lord. St James exhorts, “Whoever knows what is right to do and fails to do it, for him it is sin” (Jm 4:17). St. Paul also says in his speech to the Athenians, “The times of ignorance God overlooked, but now he commands all men everywhere to repent” (Ac 17:30). Again, Paul definitely assigns the guilt of unbelief only to those who have heard and then rejected:
For a man believes with his heart and so is justified, and he confesses with his lips and so is saved … But how are men to call upon him in whom they have not believed? And how are they to believe in him of whom they have never heard? … So faith comes from what is heard, and what is heard comes by the preaching of Christ. But I ask, have they not heard? Indeed they have; for ‘Their voice has gone out to all th earth, and their words to the ends of the world’ … Again, I ask, did Israel not understand?” (Rom 10:10-21)
Here, Paul even implies that understanding is a key element to culpability, not just the fact of hearing.