How do you know what is a "grave matter"?

I am aware of the criteria for mortal sins. However: I sometimes come across different statements of what sins are grave and what is not. For example, the Priest at home says that you go to hell if you miss Sunday Mass. Others say that kissing in a sensual way is a “grave matter” etc.

How do they know? Of course it violates the Commandments and The Preaching on the Mountain etc. but does not that go for traditionally venial sins also (stealing a cookie for example)? Did the Church ever bind certain sins (missing Mass for example) to be mortal?


Per the Catechism:

**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.

Thank you for your reply sw85!

I know this definition but it is not very clear. Missing Sunday Mass and stealing a cookie both fit in here, but only the first is traditionally considered a “grave matter”. How do the people who claim this know? How can my Priest be so sure that we go to hell if we miss Sunday Mass for example?

I am not saying he is wrong, I just want to know how he can be so sure…

You’re very welcome.

The thing is, “stealing a cookie” is a specific species of the broader genus of “theft.” Theft itself is grave matter, but circumstances may mitigate it. Stealing a car is a bigger deal than stealing a cookie. But deliberately stealing a cookie out of sheer spite, malice, and/or gluttony is a bigger deal than stealing a cookie because you’re extremely hungry.

Likewise, missing Mass is objectively grave matter, but deliberately skipping Mass because you hate the Church is a bigger deal than missing Mass because you didn’t want to get out of bed, which is a bigger deal than missing Mass because you had the schedule mixed up in your head, etc.

In other words, theft is always grave matter, it’s just not always a mortal sin.

the gravity of stealing a cookie is going to depend a the circumstances. If that cookie is the only food a person has, then stealing it from him is a very grave matter indeed.
The gravity of matter is measured by the harm done.

In determining harm done there are two aspects…Harm to others and Harm to self.
Harm to others is fairly straight forward and more easily categorized. In the above example stealing a cookie from mom’s cookie jar is one thing. Stealing the last cookie in the house of a starving family is something else entirely.

Harm to self is more difficult, and in some ways more severe.
If I know that stealing is a sin why would I freely choose to do it - large OR small.
For this reason, even a small theft with full knowledge and free consent is more grave - more spiritually damaging than a larger theft committed in ignorance or under duress.

The best answer to this cunundrum is…If you know it’s wrong…large or small…Don’t do it.


I don’t think the question has really been answered. In my opinion and thought, it is case by case, person by person, circumstance by circumstance. I think the Holy Spirit will lead your heart to know if it is a mortal sin. We all know the difference between when we sin and are like crud and feel guilty, and those sins that leave that sick feeling in our gut and eat at us.

There can be said to be “parvity of matter” in theft…(smallness of matter)

NOTE also


The obligation of the Decalogue

2072 Since they express man’s fundamental duties towards God and towards his neighbor, the Ten Commandments reveal, in their primordial content, grave obligations. They are fundamentally immutable, and they oblige always and everywhere. No one can dispense from them. The Ten Commandments are engraved by God in the human heart.

2073 Obedience to the Commandments also implies obligations in matter which is, in itself, light. Thus abusive language is forbidden by the fifth commandment, but would be a grave offense only as a result of circumstances or the offender’s intention.


2181 The Sunday Eucharist is the foundation and confirmation of all Christian practice. For this reason the faithful are obliged to participate in the Eucharist on days of obligation, unless excused for a serious reason (for example, illness, the care of infants) or dispensed by their own pastor.119 Those who deliberately fail in this obligation commit a grave sin.

One forms ones conscience with Sacred Scripture, the Teachings of the Church (such as the Catechism, and the Compendium of the Catechism, Teachings of the Popes etc) one can study orthodox Catholic moral theology …etc etc etc

We need yes reason, good formation of conscience, the guidance of the Holy Spirit–particularly through the Teachings of the Church, and virtue etc so we may face the various contingent events of life --and know how to do good and avoid evil how to follow Christ …

Certain contingent aspects can yes enter into various moral questions. It is important to note that we need to keep in mind that the circumstance is not the main aspect. And there is much that is “objective” and “given” in things dealing with morality that we apply - such as “you should not murder” --I need to not murder here and now. And while emotions (feelings) can enter in -they may not and may even mislead us. Conscience – is about the practical (here and now I am to do this or I did that and should not have) judgment of the reason (keeping in mind of course that we are to form our conscience with the Teaching of the Church etc)

One forms ones conscience with Sacred Scripture, the Teachings of the Church (such as the Catechism, and the Compendium of the Catechism, Teachings of the Popes etc) one can study orthodox Catholic moral theology …a good regular confessor who thinks with the Church etc etc etc

Grave matter is, as a category, objective. Examples of grave matter have named by the Church.
Sin, as a category, has an element of subjectivity to it, in that awareness/knowledge + a free assent of the will, in the context of that, is necessary for the grave matter to be sinful as regards that individual.

Ignorance can mitigate sinfulness. Nevertheless, all confirmed Catholics are required to become informed as to what is and is not grave matter, so even should they engage in grave matter while being “unaware,” there could be a level of culpability regarding willful or careless refusal to become educated. (A separate serious matter.)

Even non-believers have a conscience and are subject to universal moral law, so culpability can even arise (though outsiders would not know that level) in those cases.

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