Sometimes an act which is objectively morally disordered is committed with a sincere but mistaken conscience, such that it is not also an actual sin. Only actual sins include guilt and deserve punishment.
“Conscience frequently errs from invincible ignorance without losing its dignity.” [Second Vatican Council, Gaudium et Spes 16].
If the person’s conscience did not realize, and, given the limitations of fallen human persons, could not realize, in the immediate situation, that the act was a sin, this lack of knowledge is called invincible ignorance. Without some knowledge and some deliberate use of free will, an objective sin is not also an actual sin. And for an act to be an actual mortal sin, the knowledge and deliberation must be full, and the act must be gravely immoral.
It is difficult for the fallen sinner to realize, based on reason alone, that certain acts are sins. If the fallen sinner is a non-Catholic Christian, he or she may be confused by the conflicting teachings and opinions of different Christian denominations and teachers. If the person is a Catholic, he or she may be confused by the conflicting teachings and opinions of different Catholic leaders. Sometimes a Church teaching, which seems objectively clear to me, may seem confusing or difficult to interpret to others.
But, in my theological opinion, some human acts are so clearly and thoroughly immoral as to be beyond the ability of any conscience, of a person who is in their right mind, to mistakenly think these acts to be moral. These acts would include genocide, terrorism, and any sin that is committed with a full and severe malice. For no one can mistakenly think that such a malice would be compatible with the love of God and neighbor.
It is difficult to draw the line between those grave sins that might be chosen by a sincere but mistaken conscience, and those that are beyond the pale. However, I think that quite a few grave sins might be chosen with invincible ignorance.
An atheist might have invincible ignorance that God exists, especially because so many believers do not live up to the high calling of their respective faiths. And it might be very difficult for someone who is raised in one religion, seeing the good of the sincere believers of that faith, to realize that Christianity is the truest form of religion, and that Catholicism is the fullness of Christianity.
As for persons who profess to be Catholic, or who have fallen away from Catholicism, it may be difficult for them to realize that the teachings of the Church are true, when so many good persons in society do not accept certain teachings on morality. A divorced and remarried Catholic might not realize that his or her second union is not a valid Sacrament of marriage. And many Catholics, unfortunately influenced by sinful secular society, have accepted certain false teachings of society, which are contrary to Catholic teaching, such as on gay marriage, or homosexuality, or various sexual sins.
On the other hand, even when an act might be chosen by a fallen sinner with a sincere but mistaken conscience, it is probably not the case that all persons who have chosen that objective sin are absolved from guilty by invincible ignorance. Some atheists might choose atheism with culpability. Perhaps some of them don’t wish to sincerely consider whether God exists, because such an admission would require them to change their lives. And the same might be said for persons who commit various sexual sins. They know that if they accept Church teaching, they will face some difficulties in life.
It is a serious error, though, to assume that those divorced and remarried persons, who are committing the objective mortal sin of adultery by their second union, are guilty to the extent of an actual mortal sin. They may have a sincere but mistaken conscience. So the Church may permit them to receive Communion. I don’t favor that particular discipline, but it is within the authority of the Church to permit any baptized Christian to receive Communion who is believed to be in the state of grace.
It is also a serious error to assume that all persons who have sufficient accurate knowledge of Christianity or Catholicism, and yet do not convert, are guilty of actual mortal sin. Their objective mortal sin in failing to convert may not also be an actual mortal sin, due to invincible ignorance. So it is false to say that all such persons are condemned to Hell, unless they repent and convert.
Only unrepentant actual mortal sin condemns to Hell. The sin of “original sin alone” is the actual mortal sin of omission of never having found sanctifying grace, despite ample opportunity. Since it is a special type of actual mortal sin, the assertion is true that only persons guilty and unrepentant from one or more actual mortal sins can be condemned to Hell.
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