Scripture speaks of two types of sin: “sin which is mortal” and “sin which is not mortal” (1 John 5:16-17). The latter of these, the Church calls venial (or pardonable) sin. So what it is that makes a sin mortal (or deadly)?
Three conditions must be met:
(1) it must be a “sin whose object is grave matter,”
(2) it must be committed with “full knowledge,” and
(3) it must be done with “deliberate consent.”
Otherwise, you’re looking at an action which, although still objectively wrong,* is either venially sinful or not sinful at all. But how likely is it that our sins will meet all three criteria?
According to some priests and theologians, nearly impossible. For instance, the late Fr. Jim Rude, S.J. wrote an essay in 2016 entitled “Mortal Sins Are Very Difficult to Commit,” in which he recalled his habit of going to confession every Saturday during his teenage years. Instead of recalling this pious practice (one explicitly encouraged by the Church) fondly, he lamented, “Those confessions were rather sad, for there were usually mortal sins mentioned, but looking back on it I believe that there were never any mortal sins,” reasoning that “I was only fifteen and had no clue what a mortal sin was.”
Fr. Rude’s own description testifies against this: he was doing something as a teenager that he knew he wasn’t supposed to be doing, and subsequently confessing it. As he said, “there were usually mortal sins mentioned.” So it’s hard to believe that he “had no clue what a mortal sin was.” But according to Fr. Rude,
A mortal sin is not simply some evil action, an action which is truly evil, but it is one that has to be done with the deepest understanding of God’s relationship to the doer’s situation. The doer has to understand who God is, his ultimate and eternal love, and the doer has to be saying to himself, “I know who God is and what he should mean to me, and I don’t care. Away with God! I’m going to rob or hurt or sex no matter what.”
This is a gross distortion—and nearly an inversion—of the Church’s actual teaching. In Fr. Rude’s vision of morality, it would seem that the gate is wide and the way is easy that leads to heaven. But this is the polar opposite of what Jesus says in Matthew 7:13. If mortal sin is possible only to one “with the deepest understanding of God’s relationship to the doer’s situation,” then nonbelievers and the spiritually lukewarm would seemingly be saved, since they lack such an understanding.
It’s hard to square Fr. Rude’s idea that mortal sin requires a conscious rebellion from God with Jesus’ own words on the matter. Foretelling his words of condemnation to the damned, Jesus says that they will say, “Lord, when did we see thee hungry or thirsty or a stranger or naked or sick or in prison, and did not minister to thee?” (Matt. 25:44). That is, many of the damned won’t have thought that their hatred of neighbor was a hatred of God. St. John warns against this delusion, saying, “If any one says, ‘I love God,’ and hates his brother, he is a liar; for he who does not love his brother whom he has seen, cannot love God whom he has not seen” (1 John 4:20).
The position advocated by Fr. Rude has been explicitly condemned repeatedly by the Church, particularly by St. John Paul II. For instance, in Reconciliatio et Paenitentia, he cautions that “care will have to be taken not to reduce mortal sin to an act of ‘fundamental option’—as is commonly said today—against God, intending thereby an explicit and formal contempt for God or neighbor.” That is, the Church has never taught (and in fact, quite explicitly denies) that the doer has to say, “Away with God!” for his sin to be mortal. After all, the pope explained,
Mortal sin exists also when a person knowingly and willingly, for whatever reason, chooses something gravely disordered. In fact, such a choice already includes contempt for the divine law, a rejection of God’s love for humanity and the whole of creation; the person turns away from God and loses charity. Thus the fundamental orientation can be radically changed by individual acts.
If I know that a course of action is gravely sinful, and I freely choose it, I’ve chosen some sin over God. I don’t need to make an internal speech telling God to get lost, because I’ve already done this by my actions . . . even if I try to delude myself that I can serve two masters. John Paul II thought this error serious enough that he repeated his warning in Veritatis Splendor, going on at greater length why this is a dangerous perversion of Catholic mortal theology.
But Fr. Rude didn’t just have a nearly impossibly high bar for “full knowledge.” His idea of consent was also exaggerated to such an extent that he imagined that priest-killing might not be mortally sinful. That might sound like an uncharitable interpretation of his ideas, but that’s his actual example:
But also the doer has to act with full freedom. I look at articles in the news these days, like the twelve-year old who killed an eighty-two-year old priest while he was saying Mass, and I wondered what the kid was really doing, what he was really thinking. As horrible as his action was, I simply have a hard time believing that the kid committed a mortal sin by Catholic standards. And I look at people who grew up with horrible abuse during their childhood or poverty or continual gang experiences, and I wonder if they are really free to act in such an evil way.
It is true that “imputability and responsibility for an action can be diminished or even nullified by ignorance, inadvertence, duress, fear, habit, inordinate attachments, and other psychological or social factors” (CCC 1735). It’s one reason we shouldn’t condemn others for their actions: we don’t know what sort of factors might be going on behind the scenes. But we also shouldn’t prejudge in the opposite direction, as if those who grow up in poverty no longer have free will or agency, or even the ability to sin.
John Paul II reminds us that “some sins are intrinsically grave and mortal by reason of their matter,” actions which “per se and in themselves, independently of circumstances, are always seriously wrong by reason of their object. These acts, if carried out with sufficient awareness and freedom, are always gravely sinful.” If murdering a priest while he’s saying Mass doesn’t meet this criterion, it’s hard to say what would.
As penitents, where does this leave us? Quite simply, we are “obliged to confess in kind and number all grave sins committed after baptism and not yet remitted directly through the keys of the Church nor acknowledged in individual confession, of which the person has knowledge after diligent examination of conscience.” And if you’re not sure if it’s a mortal sin or not, confess it, since “it is recommended to the Christian faithful that they also confess venial sins” (Code of Canon Law, can. 988). And even if you haven’t committed any mortal sins of which you’re aware, get in the habit of going to confession nevertheless! After all, “deliberate and unrepented venial sin disposes us little by little to commit mortal sin” (CCC 1863).
For their part, the Church reminds priests that they “should be careful not to discourage the faithful from frequent or devotional confession” and that “it must be absolutely prevented that individual confession should be reserved for serious sins only, for this would deprive the faithful of the great benefit of confession and would injure the good name of those who approach the sacrament simply.”
Finally, if you have good reason to believe you’ve committed a mortal sin, and you go to confession, that’s not (as Fr. Rude puts it) “rather sad.” It’s rather (as Jesus puts it) a cause of great celebration, as “there will be more joy in heaven over one sinner who repents than over ninety-nine righteous persons who need no repentance” (Luke 15:7).
* Moral culpability is only one aspect of the question. Actions are sinful because they harm us and others, and so even when we do the wrong thing innocently (and thus, without moral guilt), we might still be harming ourselves. Take a couple fooled (by the culture or even their priest) into believing that it is okay, or even morally responsible, to use contraception. They might be innocent of any moral guilt, but the damage done to their marriage and their families remains.