How do I distinguish between mortal and venial sin?


I know that some things are cut-and-dry grave matter and likely mortal sin. But how can I tell if some sins are mortal or venial, for example, sinful thoughts?

I have trouble distinguishing and I do not want to offend Christ by receiving the Eucharist in the state of mortal sin. But how can I tell? I also need to know how to tell what I should confess.

Thank you & God bless,


I don’t have an answer really. I just want to say that I’m so glad you asked this. I, too, have a little bit of a hard time with this. Especially when explaining to my children. I know if it’s mortal you have to have full knowledge it’s a serious sin against God’s laws, and you do it anyway. A venial sin is a small disobedience against God’s law or it’s a serious sin, but the person is not aware that it’s a serious sin, or a person is coerced into a serious sin by someone or something else. I would like to know what a small act of disobedience against God’s law might be.

Good Question


You cannot offend God by receiving the Eucharist unless you are conscience of having committed mortal sin and you have not received sacramental absolution, yet you receive Communion despite what your conscience is telling you.

So the answer comes from you and what God is telling you in your conscience.

Your responsibility is to inform your conscience, then follow it.

“Conscience is man’s most secret core, and his sanctuary. There he is alone with God whose voice echoes in his depths” (CCC 5, Gaudium et Spes 16). “Conscience can remain in ignorance or make erroneous judgments. Such ignorance and errors are not always free of guilt.” (CCC 1801) “Faced with a moral choice, conscience can make either a right judgment in accordance with reason and the divine law or, on the contrary, an erroneous judgment that departs from them.” (CCC 1786) “A human being must always obey the certain judgment of his conscience.” (CCC 1800)

The Catechism of the Catholic Church gives you a rule of thumb with which you can examine your conscience:

“When the will sets itself upon something that is of its nature incompatible with the charity that orients man toward his ultimate end, then the sin is mortal by its very object . . . whether it contradicts the love of God, such as blasphemy or perjury, or the love of neighbor, such as homicide or adultery. . . . But when the sinner’s will is set upon something that of its nature involves a disorder, but is not opposed to the love of God and neighbor, such as thoughtless chatter or immoderate laughter and the like, such sins are venial” (Catechism of the Catholic Church, 1856, St. Thomas Aquinas, STh I-II,88,2)

And from the Balitmore Catechism, no. 4, which is a little more explanatory…

54. Q. What is mortal sin?

A. Mortal sin is a grievous offense against the law of God.

**“Grievous” **that is, very great or serious. **“Against the law.” **If
we are in doubt whether anything is sinful or not, we must ask ourselves: is it forbidden by God or His Church? and if we do not know of any law forbidding it, it cannot be a sin, at least for us.

Suppose, for example, a boy should doubt whether it is sinful or not to fly a kite. Well, is there any law of God or of His Church saying it is sinful to fly a kite? If not, then it cannot be a sin. But it might be sinful for another reason, namely, his parents or superiors might forbid it, and there is a law of God saying you must not disobey your parents or superiors. Therefore a thing not sinful in itself, that is, not directly forbidden by God or His Church, may become sinful for some other reason well known to us.

We must not, however, doubt concerning the sinfulness or lawfulness of everything we do; for that would be foolish and lead us to be scrupulous. If we doubt at all we should have some good reason for doubting, that is, for believing that the thing we are about to do is or is not forbidden. When, therefore, we have such a doubt we must seek information from those who can enlighten us on the subject, so that we may act without the danger of sinning.

It is our intention that makes the act we perform sinful or not. Let me explain. Suppose during Lent a person should mistake Friday for Thursday and should eat meat-that person would not commit a real sin, because it is not a sin to eat meat on an ordinary Thursday. He would commit what we call a material sin; that is, his action would be a sin if he really knew what he was doing. On the other hand, if the person, thinking it was Friday when it was really Thursday, ate meat, knowing it to be forbidden, that person would commit a mortal sin, because he intended to do so.

Therefore, if what we do is not known to be a sin while we do it, it is no sin for us and cannot become a sin afterwards. But as soon as we know or learn that what we did was wrong, it would be a sin if we did the same thing again. In the same way, everything we do thinking it to be wrong or sinful is wrong and sinful for us, though it may not be wrong for those who know better. Again, it is sinful to judge others for doing wrong, because they may not know that what they do is sinful. It would be better for us to instruct than to blame them. The best we can do, therefore, is to learn well all God´s laws and the laws of His Church as they are taught in the catechism, so that we may know when we are violating them or when we are not, i.e., when we are sinning and when we are not.


Sacred Scripture the following acts are considered gravely sinful:. evil thoughts, fornication, theft, murder, adultery, coveting, wickedness, deceit, licentiousness, envy, slander, and pride (cf. Mk. 7:21-23; Mt. 15:19); blasphemy, idolatry, impure actions, jealousy, anger, envy, and drunkenness (cf. Gal. 5:19; cf. Eph. 4:17-32; Col. 3:5-10; 1 Thess. 4&5). The New Testament gives numerous lists of sins that are grave to the life of the soul and that break one’s relationship with God (cf. Mt. 5:1-17, 6:2; 12:31; 15:1-10; Mk. 10:19; Lk. 18:20; Rom. 1:29-31; 13:13).


Dear Dave,

Thank you so much for your thorough response. I guess the trouble I have is that I have a mild tendency toward scrupulosity.

[quote=itsjustdave1988]So the answer comes from you and what God is telling you in your conscience.

Your responsibility is to inform your conscience, then follow it.

My conscience is very well-informed (I could probably tell you all the required rules to follow), I’m just not sure how to tell when to trust it. I have always been a worrier :o , and I worry about whether some things are sinful. I am trying to overcome this, but it is very hard when I lack guidance.

[quote=itsjustdave1988]In the same way, everything we do thinking it to be wrong or sinful is wrong and sinful for us, though it may not be wrong for those who know better.

This is very vague and for someone with a scrupulous conscience, it only makes things worse. I know that you were just trying to help. Maybe I should have included that factor in my first post.

I have read sources on scrupulosity saying that the best thing to do is get a consistent confessor/spiritual director. Unfortunately, I only have access to 2 priests at the moment (and limited at that). Both of them have theologically liberal views and I would not trust them for orthodox spiritual direction. (eg. they would probably think it’s a sin to believe that women should not be allowed to become priests, but they think that homosexual behavior is not a sin) :confused: .

Thank you for your help!



I worry about whether some things are sinful. I am trying to overcome this, but it is very hard when I lack guidance.

I understand. I’m tending to be more of a rigorist myself. Better rigorism than laxism, I think, when it comes to examining your own conscience. Yet, those who tend to be overly scrupulous ought to always understand and truly believe that contrition of charity remits all sin. Keeping this in mind will help to calm your fears that perhaps you think you may not be in a state of grace. If your sorrow for sin is primary due to your love for God, you are in a state of grace. Nonetheless, for licit reception to the Sacrament of the Eucharist, you also need sacramental absolution, not just contrition of charity.

Also, I like to keep these words of St. Athansius in mind when I tend toward being overly scrupulous…

**St. Athanasius (ca. AD 358): **“when someone falls from the Spirit through any wickedness—that grace indeed remains irrevocably with those who are willing to repent after such a fall.”(Discourses Against the Arians, 3, 24-25, ca. AD 358 )


As a general rule of thumb,

a mortal sin is in someway a deliberate violation of the 10 Commandments. (theft, heresy, immorality\adultery, deceit…)

A venial is not living up to the Beatitudes.


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