Sufficent reflection for mortal sin



Just wondering in the case of mortal sin:

  • Do you have to know you are committing a mortal sin at the time, or do you just have to know you are doing something wrong. What if you willfully decide to do something wrong, knowing that its wrong, but not knowing that it is a mortal sin.

Any comments…


One of the three requirements for any act to be a mortal sin is to know that the matter is grave. I’m sure that many Catholics know that using birth control is wrong but do not realize the seriousness of the action. Culpability would be reduced in this situation. CCC 1857



That clarifies a lot.


Hi backtocatholic,

Here are the conditions for a mortal sin:

For a sin to be mortal, three conditions must exist at the same time:

  1. It must be of a grave matter;
  2. It must be committed with full knowledge that it is a mortal sin;
  3. It must be committed with full consent. [Full consent means to do it “voluntarily.”] (C.C.C. # 1857)

Before I go to Confession, I review my sins using an “Examination of Conscience.”

These “Examinations” help me to “jog my memory” on what kinds of sins I have committed since my last Confession.

You can either find one on-line, or sometimes the church that you are going to for Confession may even have them out during Confession time, so that you can use them before going to Confession.

Or, you can even buy a booklet at your local Catholic book store, too.


Hi. From your replies it would appear that it’s quite difficult to commit a mortal sin. Also do u have to actively reflect in your mind that what you are doing is gravely wrong but decide to so it anyhow or is an inkling at the back of your mind enough.

Finally from looking at other posts on this board I’ve seen opinions vary from people saying that it’s rare for all 3 conditions to be met together to a general feeling that mortal sins are very common.

I would welcome any opinions.


Hi again backtocatholic,

I will try my best to answer your questions. :slight_smile:

Sometimes I think that it is possible to not know that we are committing a mortal sin. That is why I recommend doing an “Examination of Conscience.” We could be committing one out of ignorance–not knowing any better.

Sometimes someone could deliberately know that what they are doing is wrong, but still decide to commit the sin anyway.



I think I may not have phrased my question properly.

Since coming back to the church I have looked at various examinations of conscience, lists of mortal sins etc. Indeed at that time there were many things that I was not aware that were mortal sins.

However, it seems that the better I acquaint myself with this the more confused I get.

I understand that there are some sins that are always grave matter e.g. missing mass on Sunday without a valid reason, and that there are many (in fact probably most) sins that may be venial or mortal depending on the gravity. A good example is the current thread about gluttony.

My problem is that while I understand the theory of the 3 conditions for grave matter, it’s the practical application of them that gives me a problem.

Many people on this site have said that while you might not be aware that something is grave matter, you would always be aware that you are committing a mortal sin, due to the condition of sufficient reflection.

A simple definition seems to be that if you knowingly and willingly do something that you know to be serious (grave matter) then it is a mortal sin. Based on this, it would seem that mortal sins are quite difficult to commit and that there would be no doubt.

My problem is that I tend to worry that everything i do is a mortal sin.

The question I was asking was does sufficient reflection mean that you have thought about the act (even momentarily), realised the gravity of the act and done it anyhow (knowing you are committing mortal sin), or does a nagging feeling at the back of your mind that you are doing something wrong suffice.

The reason I am asking this is that I always thought that mortal sins were quite rare and that if you obey the obvious rules that you should be fine. However, there is often a lot of discussion on this site about mortal sin, leading me to believe they are more common than I think.


Hi again backtocatholic,

I am sorry if I misunderstood anything that you were trying to ask.

I personally don’t think that mortal sins are all that uncommon.

I think that there are some mortal sins that are more obvious than others, that we know about. Murder would be one example, and adultery would be another one.

I guess the best thing that I can tell you, is that if you aren’t sure about the kind of sin that you are committing, it would be best to ask the priest the next time you go to confession.

I guess the thing too about mortal sins is their gravity. To commit them, you have to be willful about it, and knowingly do it. You have to pretty much know that what you are doing isn’t right.

I am not sure that I am doing a good job of explaining this very well, but you have to be in full consent to commit them–pretty much know what you are doing.

I understand what you are saying about “a nagging feeling at the back of your mind,” but I guess in my mind that may not matter, as long as you know fully that what you are still doing is wrong, but decided to do it anyway, if that makes sense. You have to fully engage your will, and then take action on it, in order to commit the sin.


That’s great. Thanks


You’re welcome. :slight_smile:

closed #11

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