I’m currently writing a post on purgatory & praying for the dead, where I’ll be explaining and defending these Catholic beliefs, but I thought it would be helpful to share some prerequisite information first. Understanding the distinction between mortal sin and venial sin will make it easier to understand purgatory, so here I’ll briefly explain this distinction and why we believe it exists.

Mortal sins are sins which lead to spiritual death (the word “mortal” literally means “deadly” or “causing death”) — when one commits a mortal sin, he is dead to God, totally cut off from the Divine Life. Venial sins, on the other hand, do not separate us totally from God, but damage our relationship with Him. To use marriage as an analogy: venial sin is like a person doing something that harms their relationship with their spouse in some way, doing damage to the marriage while still remaining in marital union with them, while mortal sin is like getting a divorce, ending the relationship entirely. Of course, because God is so merciful, He will always welcome back those who “divorced” themselves from Him if they repent of their sins (we’ll get into the details of this in a future post on the Sacrament of Reconciliation).

What constitutes a mortal sin? The Catechism of the Catholic Church explains:

1857 For a sin to be mortal, three conditions must together be met: “Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent.”

1858 Grave matter is specified by the Ten Commandments, corresponding to the answer of Jesus to the rich young man: “Do not kill, Do not commit adultery, Do not steal, Do not bear false witness, Do not defraud, Honor your father and your mother.” The gravity of sins is more or less great: murder is graver than theft. One must also take into account who is wronged: violence against parents is in itself graver than violence against a stranger.

1859 Mortal sin requires full knowledge and complete consent. It presupposes knowledge of the sinful character of the act, of its opposition to God’s law. It also implies a consent sufficiently deliberate to be a personal choice. Feigned ignorance and hardness of heart do not diminish, but rather increase, the voluntary character of a sin.

1860 Unintentional ignorance can diminish or even remove the imputability of a grave offense. But no one is deemed to be ignorant of the principles of the moral law, which are written in the conscience of every man. The promptings of feelings and passions can also diminish the voluntary and free character of the offense, as can external pressures or pathological disorders. Sin committed through malice, by deliberate choice of evil, is the gravest.

So, for a sin to be mortal it must be a grave matter, and it must be committed with full knowledge and with deliberate consent of the will. If any of these conditions aren’t met, the sin is not mortal but venial (the word “venial” simply means “pardonable”). There are varying levels of severity within the categories of mortal sin and venial sin, as well, meaning that some mortal sins are worse than others and by that fact merit greater punishment, and likewise with venial sins. Also important to understand is that those who die in a state of unrepentant mortal sin go to hell, while those who die with only venial sins will ultimately end up in heaven (we’ll take a closer look at these topics in my upcoming post on purgatory).

How do we know that this kind of distinction between the severity of sins exists, though? Or that things like ignorance can reduce a sin’s severity, as the Catechism says? We know, at least in part, because Scripture tells us so.

If any one sees his brother committing what is not a mortal sin, he should pray to God and He will give him life for those whose sin is not mortal. There is sin which is mortal; I do not say that one is to pray for that. All wrongdoing is sin, but there is sin which is not mortal.

— I John 5:16-17

This is one of the most straightforward passages on mortal sin, and it’s where we derive the term itself. John plainly tells the faithful that some sin is mortal and some is not. If someone commits a non-mortal sin, we are to pray for them and God will “give them life”; but if someone commits a mortal sin, we are not to pray for them. Why not? John doesn’t say, so thank the Lord for giving us a Church to act as a living teaching authority. The Church teaches that prayers for those in mortal sin are ineffective because they are spiritually dead, so our prayers couldn’t help them — it would be like administering medicine to a corpse. Unless and until the person willfully repents and returns to life in Christ, they are beyond our help.

Another important Scripture passage is in chapter five of the Gospel of Saint Matthew, where Christ himself makes the following statement:

“Do not think that I have come to abolish the law or the prophets. I have come not to abolish but to fulfill. Amen, I say to you, until heaven and earth pass away, not the smallest letter or the smallest part of a letter will pass from the law, until all things have taken place. Therefore, whoever breaks one of the least of these commandments and teaches others to do so will be called least in the kingdom of heaven. But whoever obeys and teaches these commandments will be called greatest in the kingdom of heaven.”

— Matthew 5:17-19

Here, Jesus says that it’s possible to break some commandments — to sin — and still enter the kingdom of heaven, albiet in a lesser capacity than one would otherwise attain (another topic for another time). Yet elsewhere in Scripture we find lists of sins which, if committed, will prevent us from entering the kingdom of God at all.

• “Do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived; neither fornicators, nor idolaters, nor adulterers, nor the effeminate, nor sodomites, nor thieves, nor the greedy, nor drunkards, nor revilers, nor robbers will inherit the kingdom of God.” (I Corinthians 6:9-10)
• “Now the works of the flesh are plain: immorality, impurity, licentiousness, idolatry, sorcery, enmity, strife, jealousy, anger, selfishness, dissension, party spirit, envy, drunkenness, carousing, and the like. I warn you, as I warned you before, that those who do such things shall not inherit the kingdom of God.” (Galatians 5:19-21)
• “Be sure of this, that no fornicator or impure man, or one who is covetous (that is, an idolater), has any inheritance in the kingdom of Christ and of God. Let no one deceive you with empty words, for it is because of these things that the wrath of God comes upon the sons of disobedience.” (Ephesians 5:5-6)
• “But as for the cowardly, the faithless, the polluted, as for murderers, fornicators, sorcerers, idolaters, and all liars, their lot shall be in the lake that burns with fire and brimstone, which is the second death.” (Revelation 21:8)

These are nothing less than lists of mortal sins. And we find other places in Scripture where distinctions are made between sins that have various levels of severity, as well as references to the idea that those sins are less severe which we commit in ignorance.

• “But I say to you that every one who is angry with his brother shall be liable to judgment; whoever insults his brother shall be liable to the council, and whoever says, ‘You fool!’ shall be liable to the hell of fire.” (Matthew 5:22)
• “And that servant who knew his master’s will, but did not make ready or act according to his will, shall receive a severe beating. But he who did not know, and did what deserved a beating, shall receive a light beating. Every one to whom much is given, of him will much be required; and of him to whom men commit much they will demand the more.” (Luke 12:47-48)
• “And Jesus said, ‘Father, forgive them; for they know not what they do.’ . . .” (Luke 23:34)
• “Jesus said to them, ‘If you were blind, you would have no guilt; but now that you say, ‘We see,’ your guilt remains.'” (John 9:41)
• “. . .therefore he who delivered me to you has the greater sin.” (John 19:11)
• “I formerly blasphemed and persecuted and insulted him; but I received mercy because I had acted ignorantly in unbelief.” (I Timothy 1:13)
• “For if we sin deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins,” (Hebrews 10:26)
• “. . .for you know that we who teach shall be judged with greater strictness.” (James 3:1)

As you can see, Scripture is full of passages that support the Church’s teaching regarding mortal and venial sins. But it’s always important to point out that the Bible is not our sole authority on Christian doctrine, so something need not be found in Scripture in order for Christians to believe it. Obviously our beliefs cannot contradict Scripture, because truth cannot contradict truth; but Scripture doesn’t contain every single truth, or an explanation of every single Christian belief, and it was never intended to (I get into this topic a bit more in What the Bible Is Not, Part II: Protestant Misconceptions). Ultimately, we believe what the Church teaches about mortal and venial sin for the same reason we believe her other teachings: because she teaches with divine authority, bestowed upon her by Christ himself.

I hope this explanation has been helpful. Frankly, this is one of many topics on which I cannot understand the Protestant position, which is essentially that all sin is equally grave. The notion that some sins are worse than others is not only spoken about frequently in Scripture, but it’s downright intuitive. Theft and murder are both sins, sure, but we recognize that in terms of severity and evil there is a chasm between stealing someone’s watch and murdering their child.

While all sins are offenses against God, Who is infinitely good, and therefore require infinite restitution for which no man could ever atone (that’s where Christ comes in), we can still recognize that certain sins involve greater malice on the part of the one committing them — and I think that might be the key to understanding this distinction. Mortal sin is deadly to us, not to God; our sins, no matter how severe, cannot harm God, because nothing can. The reason that some sins are worse than others is because they do more harm to the sinner, to his soul. And the reason that some sins merit worse punishment than others is because they indicate greater evil within the sinner, and justice demands greater punishments for greater evils. You may be wondering: “But didn’t Jesus take the punishment for all the sins of mankind when he was Crucified? Why would we still be punished for our sins if Christ took on our punishment?” This is a misunderstanding based on the theological errors that have developed out of Protestantism, a topic which I’ll be writing more about soon.

Another important aspect to consider is that our sins always harm other people in various ways, whether directly or indirectly, so this too merits various levels of punishment, as well, based on how much our sins harm others. Recently I listened to a discussion that the wonderful Catholic philosopher Peter Kreeft had with Dr. Jordan B. Peterson (which you can listen to here), and towards the end of their conversation Kreeft recalled a saying which he said is popular among Russian Orthodox mystics:

If you go home this afternoon and do one deed of genuine sacrificial charity to your neighbor, the result will be that hundreds of years from now someone on the other side of the world, whom you’ve never dreamed of, will have enough grace to overcome his trials — and if you don’t, he won’t. And if you do one deed of harm to an innocent human being, then someone on the other side of the world, hundreds of years from now, will fall because of your fall.

This anecdote is meant to emphasize a profound truth: that all Christians are connected in ways far more direct and intimate than most of us imagine. While it’s true that all of mankind is connected socially, the connection between Christians far exceeds this basic human connection, because we are not just living together socially, we are joined together in one living Body — the Mystical Body of Christ. Everything that happens within some part of your body affects the whole in some way, and this is absolutely true for us as members of Christ’s Body. Our sins harm not only ourselves, but the entire body of Christ. This is a hard truth, because it places an immense responsibility upon us to act uprightly. But in this cushy, hedonistic, nihilistic world we’re currently living in, I think more responsibility is exactly what most of us need.

And remember, while our sins damage the entire body of Christ, likewise do our good deeds benefit the entire body of Christ. We may have the potential to do a great deal of evil, but we also have the potential to do a great deal of good. Let us take our potential seriously, and behave accordingly.

God love you.