Question: “I recently heard someone say that there are three categories of sin: mortal, serious and venial. I thought there were only two: mortal and venial. Can you enlighten me?”
You are right. When sins are classified by reason of their gravity and their effects, there are only two categories: mortal and venial.
Pope John Paul II dealt with the issue in section 17 of his Apostolic Exhortation Reconciliatio et paenitentia in 1984.
He points out that already in the Old Testament there were certain sins – various forms of impurity (cf. Lv 18:26-30), idolatry (cf. Lv 19:4), the worship of false gods (cf. Lv 20:1-7), etc – that were punished by the person being “taken away from the people”, which could also mean condemned to death (cf. Ex 21:17). In other words, they were mortal sins.
As regards the New Testament, the Pope comments especially on two passages. One of them is in the first letter of St John, where the distinction is made between sin which is “deadly”, or mortal sin, and sin which is “not deadly”, venial sin.
The Pope comments: “St John speaks of a sin which leads to death (pros thanaton), as opposed to a sin which does not lead to death (me pros thanaton; cf. 1 Jn 5:16f.). Obviously, the concept of death here is a spiritual death. It is a question of the loss of the true life or ‘eternal life,’ which for John is knowledge of the Father and the Son (cf. 1 Jn 17:3) and communion and intimacy with them.”
In the other passage, Jesus himself speaks of a “blasphemy against the Holy Spirit” that “will not be forgiven” (cf. Mt 12:31f.), since it consists in an obstinate refusal to be converted to the love of the Father of mercies.
Even though the sinner in this case seems to reject the very source of forgiveness, the Pope sounds a note of hope as regards their eternal salvation: “It is to be hoped that very few persist to the end in this attitude of rebellion or even defiance of God. Moreover, God in his merciful love is greater than our hearts, as St John further teaches us (cf. 1 Jn 3:20), and can overcome all our psychological and spiritual resistance. So that, as St Thomas writes, ‘considering the omnipotence and mercy of God, no one should despair of the salvation of anyone in this life’” (Summa Theologiae, II-II, q. 14, a. 3, ad primum).
Pope John Paul goes on to say that in the light of these and other passages of sacred Scripture, doctors and theologians, spiritual teachers and pastors, as well as the Magisterium of the Church, have divided sins into mortal and venial.
As regards their effects, mortal sin deprives the sinner of sanctifying grace – that is, friendship with God, charity and therefore eternal happiness – whereas venial sin does not.
And with respect to the punishment it merits, mortal sin, if unforgiven, leads to eternal punishment, whereas venial sin merits only temporal punishment, which can be made up on earth or in purgatory.
What are we to make, then, of the concept of “serious sin”? Is it a separate category, distinct from venial sin and mortal sin?
Pope John Paul says no. He acknowledges that in the Synod of Bishops that preceded his Apostolic Exhortation, some bishops suggested this third category of sin, but he rejects it: “This threefold distinction might illustrate the fact that there is a scale of seriousness among grave sins. But it still remains true that the essential and decisive distinction is between sin which destroys charity and sin which does not kill the supernatural life. There is no middle way between life and death.”
Undoubtedly, the reason for introducing the third category was to limit mortal sins to the few truly serious sins which constituted a direct rejection of God. Then all other sins, including, presumably sins like adultery, masturbation or fornication, although serious, would not kill the life of grace in the soul.
But this is a false distinction, with no basis in Scripture or the traditional teaching of the Church. Sins like adultery, masturbation and fornication have always been regarded as mortal (cf. Catechism of the Catholic Church, 2352, 2353, 2380).
In summary, sins are either mortal or venial. They kill the life of grace in the soul or they do not. As Pope John Paul says, there is no third category: there can be no middle ground between life and death.