Synonyms in moral terms: grave sin = mortal sin =serious sin

Just a little note.

Sometimes the terms “grave sin”, “mortal sin” and “serious sin” get used in a way other than the usage of the Church – which can confuse things somewhat.

They are *synonyms *in Catholic moral theology and the documents of the Church.

A grave sin is a mortal sin. A serious sin is a mortal sin. A mortal sin* is* a grave sin.

Sometimes one finds on the forum a writer saying something like --“was this a grave sin or a mortal sin?” Or “the person committed a grave sin but it was not mortal”. which can lead to the impression that a grave sin was anything other than a mortal sin.

Mortal sin and Grave sin the terms for the same sin.

grave sin = mortal sin =serious sin

It is understandable that this gets confused sometimes.

Where the confusion enters in is on the one hand- in order to *commit *a mortal sin (grave sin) one needs grave matter, full knowledge and deliberate consent.

On the other hand it is also completely correct to say things like: murder is a grave sin or adultery is a grave sin --speaking of the thing itself --in itself. Or murder is a mortal sin.

Such is a -grave, serious, mortal -sin (all meaning the same thing but with different accent).

And it is also true to say: “such and such” is a grave sin but I did not commit a grave sin when I did “such and such” for I lacked the needed knowledge or the needed consent so my sin that I committed was *venial *if there was sin.

One can also say ““such and such” is a grave matter but I did not commit the grave sin for I lacked deliberate consent --so I committed a venial sin or no sin.”

That can help keep things more clear in discussing these things (and which is what many do here of course already).

But what one does not want to say is: I committed “such and such” but without the needed deliberate consent or knowledge so I committed a grave sin but not a mortal sin.

Such would be not the right way to put it – for a grave sin* is *a mortal sin. They mean the same thing. Similarly one would not want to say “I committed a serious sin but it was not mortal”.

Best way is likely use the language that does in fact usually get used here: ““such and such” is a grave matter but he did not commit the grave sin for he lacked deliberate consent --so he committed a venial sin or no sin.”

I thought to note it again in a general way for it comes up from time to time.

Here are some short examples of usage in documents of the Catholic Church -others can be given but these are a good example for one sees the terms used together.

From: The Compendium of the Catechism issued by Pope Benedict XVI

  1. Which sins must be confessed?

All grave sins not yet confessed, which a careful examination of conscience brings to mind, must be brought to the sacrament of Penance. The confession of serious sins is the only ordinary way to obtain forgiveness." (see also Canon Law …the term is used there too).

  1. What is required to receive Holy Communion?

To receive Holy Communion one must be fully incorporated into the Catholic Church and be in the state of grace, that is, not conscious of being in mortal sin. Anyone who is conscious of having committed a grave sin must first receive the sacrament of Reconciliation before going to Communion.

One can commit a grave sin while lacking full knowledge or consent though, like say a teenage Evangelical with a habit of (or addiction to) masturbation.

Masturbation is an example of grave matter. A mortal sin must involve a grave matter along w/ full knowledge and full freedom.

If one commits something that is a grave matter but lacking the needed knowledge or the deliberate consent --one commits a venial sin (or no sin even).

(One does not* commit* a grave sin (also called a mortal/serious sin) but a *venial sin *or no sin…).

Compendium issued by Pope Benedict XVI

  1. When does one commit a mortal sin?


One commits a mortal sin when there are simultaneously present: grave matter, full knowledge, and deliberate consent. This sin destroys charity in us, deprives us of sanctifying grace, and, if unrepented, leads us to the eternal death of hell. It can be forgiven in the ordinary way by means of the sacraments of Baptism and of Penance or Reconciliation.

  1. When does one commit a venial sin?


One commits a venial sin, which is essentially different from a mortal sin, when the matter involved is less serious or, even if it is grave, when full knowledge or complete consent are absent. Venial sin does not break the covenant with God but it weakens charity and manifests a disordered affection for created goods. It impedes the progress of a soul in the exercise of the virtues and in the practice of moral good. It merits temporal punishment which purifies.

Yes the phrases may in fact be loosely used as synonyms as you say.

However I believe Moral Theologians would make fine technical distinctions which would mean these phrases are not perfectly synonymous.

For example, there are two major groups of sins of grave matter:
(a) There are those whose matter is grave “ex toto genere suo”. When committed with full knowledge and consent… they are always Mortal Sins. Full stop. These are commonly called “mortal sins” (eg blasphemy).
(b) Then there are those whose matter is grave “ex genere suo.” When committed with full knowledge and consent there are circumstances where the sin may only be venial. This is because the “matter” admits of lightness under some circumstances (eg theft of trivial amounts). Sins of this type are technically called “Grave Sins.”

Yes there is the distinction where where something “admits of parvity of matter” sure. But then that matter* there* is then * not grave matter* in the case where it does. Johnny’s theft of the little piece of candy is not grave matter, with full knowledge and deliberate consent but venial matter with full knowledge and deliberate consent --a venial sin. His confessor would not call his theft a “grave sin” but a venial sin. And the Catechism would approach things likewise.

And this is very much an aside from what I was noting in any case.

And the terms I noted above are yes synonymous (something for example Fr. John Hardon also points out in his Catholic Dictionary). Not loosely used but consistently and firmly used to mean the same thing. (What can be said is that they bring out different emphasis but mean the same sin. “Serious” emphasizes that it is well serious – not light. “Grave” too does this. “Mortal” emphasizes the effect of spiritual death. But they refer to the same reality- the same sin.)


You are trying to talk about a moral act “in itself.”
Please source a Magisterial document that even talks like this about moral acts.
This reads like “pop moral theology” to me but maybe I am wrong :shrug::eek:.

Anyhow, lets talk about an act of prostitution which is clearer.
If you used common phrases from the Catechism it would seem you are trying to say, “the offence of prostitution is in itself a mortal sin.”

No sorry.
It seems you are trying to identify a component (the object) of a complete moral act.
If you are, then the object/matter of the offence that the Church calls prostitution is not called a sin.
It is called “a disordered act” or “against right reason” or “against Natural Law.”

Why is the **object **of a moral act not called “sin”?
Its simple, only a complete moral act can be called a “sin”.
When you refer to the “object” (one of the two primary fonts of a moral act) you are no longer dealing with a complete moral act/offence/sin.
Therefore the object of a moral act can only be called a “disordered act” or something similar. Only when “the end in view/intention” is also identified do we have a complete moral act. Only then can we call the complete moral act a “sin.”

The two primary sources/fonts of a moral act (related much like matter and form) do take getting used to. Lets take another example.
Is a cadaver (the body or “matter” alone) a human being? Of course not. Is the soul (the “form” of the body) alone a human being? Many might say yes, but in fact the theologians (including Aquinas) would say no.
These two components must vivify each other before we can apply the phrase "human being to the reaility in question.

This is the philosophical error you consistently keep making.
You talk of a sin (i.e. an (im)moral act) “in itself.” Once you do this you are no longer dealing with the complete moral act but only its “matter/object” (like the cadaver in the example above). Therefore the predicate “sin” can no longer be used of this object.

The matter/object of a sinful act can only be ordered or disordered. It cannot correctly be called sinful. It certainly cannot be called “mortally sinful”.

Its a bit like your pendanticism regarding “committing” sin or “engaging” in sin is it not?
If you are going to insist on such pedanticism then you must be accurate yourself in these things.

I believe you are mistaken BookCat. You obviously do but, technically, that would contradict the definition of mortal sin in the Catechism which states that full deliberation must be involved.

One can of course distinguish between material sin and formal sin in a given particular offence. e.g. Sam materially committed adultery but formally he did not because he didn’t realise it was his wife’s identical sister.

Now you appear to say that Sam’s “act in itself” is “mortal sin”.
Well Sam’s act “in itself” is not a theologically appropriate predicate here.

However, I will humour you and assume you refer to Sam’s visible scenario above as seen by a witness. In this case then, his actions do indeed constitute “material sin” (yes he engaged in adultery) but not formal sin and so NOT “mortal sin”.

So your statement above that:
(a) mortal sin…can be used to refer to the object of a moral act is a contradiction in terms. Mortal sins must always be formal (ie imply subjective culpability), how can the object alone (ie grave matter, a disordered act) ever of itself imply culpability? Sam did not commit a mortal sin. But he did commit a gravely disordered act/offence.
(b) mortal sin…can be used to refer to formal sin Yes I probably agree with this though keep in mind the terms are not identical. Some formal sins are merely venial.

So in short your statement “mortal sin…can be used to refer to the object of a moral act” is, technically, an internal logical contradiction. It only seems to work for you because you keep confusing “the complete moral act” with but one of its two primary fonts/sources (the “object”).

I challenge you to find clear Magisterial sources (or Aquinas) identifying “grave matter” with “mortal sin” and vice-versa.

Originally Posted by Blue Horizon
It is not technically correct to try and talk about the “objective nature of a moral act” (I know what you mean but this is a very sloppy phrase) by calling it “mortal sin”.
ALWAYS the accurate/correct term in this context is “grave matter” (or, sloppily, “grave sin”).

One can speak of the “objective nature of the mortal act” (it is not a sloppy phrase) by calling it mortal sin.

One can say “adultery is a mortal sin”.

I believe you are quite mistaken.

If by adultery you mean “sex with one you are not married to” then the most you can correctly say (technically) is that adultery is gravely disordered and contradicts the Natural Law.

Older theologians may indeed colloquially say “adultery is a mortal sin” but it is really just sloppy shorthand for “adultery is a mortal sin if done in full deliberation…”
Even Aquinas is guilty of this and theologians point out exactly what I am now communicating to you.

I understand this sloppiness suits your purposes but technically you are very mistaken sorry and I cannot let your logical contradiction go unchallenged.


And again, if we “swap in” your other perfectly equivalent phrases we get:
**“Yes it is mortally sinful to engage in prostitution - and yes it is possible that the culpability may be reduced…” **
Well it doesn’t really make sense does it?
If prostitutes are sinning mortally by their acts then, by definition those acts must be fully imputable. It simply doesn’t make sense to try and weaken the imputability in the same sentence by adding “…the culpability may be reduced.”

Clearly, in this sentence, “mortally sinful” and “gravely sinful” cannot be swapped in and out with impunity ?

Tis a language thing.

Try and mount an argument :shrug:.
Until you do tis a logical contradiction in your argument that you cannot explain.
This proves you are mistaken in asserting that mortal sin and grave sin are identical :eek:.

Originally Posted by Bookcat
One can use both terms “grave sin”, “mortal sin”] … to refer to the objective nature of the act.

Yet the CCC contradicts your opinion here BookCat…
“Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent.”

I think you need to clarify in your own mind exactly what you really mean by your unusual phrase “objective nature of the act.” Are you referring to:
(a) the object of a human act alone ( ie one of the three component fonts and so not a full human act and therefore not a sin =“matter”)?
(b) a committed sin where we are only interested in looking at what the object/matter of the agent’s intent (ie a material sin)?

I think your phrase is really mixing up both the above technical definitions so that you can use the expression “mortal” to support your theory that grave and mortal are perfectly identical. But this circle cannot be squared. “Material sin” and the “matter of sin” are very different beasts sorry.

Have a look at Brertzke’s “A Morally Complex World: Engaging Temporary Moral Theology (p.67)” where he criticises the decadent Thomism (“Physicalism”) inherent in just the phrase “objective nature of the act” that you use.

Originally Posted by Blue Horizon
How about a response BookCat?

I gave my response yesterday…

No, you only replied to part of my post.
You missed out the above quesions…have another go.

Blue Horizon

This is a old thread --we are really not to bring them back to life.

What I have noted is the case (one may consult the Church documents, Canon Law, Moral Theology and Catholic Answers staff…

(And I have abundantly responded in the other thread (even it not to every line of yours --though I would note that I await responses in the other thread --but I understand time is limited…and the thread has been too long!).

I prefer not to spend any more time going round and round :wink: --this is taking too much time etc. I refer readers to my other posts.

(Also I do not plan to read through the additions to this old thread -or respond further here -my not responding is from not wishing to keep going on and on…).

I bid you a splendid Lords day!

I don’t think so…
This topic has in fact been continuouly debated between us on another thread for the intervening 5 weeks so I have put it back here where it started and is entirely more appropriate. I could start a new thread…but what would be the point?
I realise that you may personally wish to see this discussion finished but that is not really a good enough reason sorry my friend.

The best way to close it is to provide clear answers to my challenges of your increasingly internally contradictory position on this matter.

Unargued appeals to your own personal authorities (or your own interpretation of very hard to find Magisterial sources taken completely out of context) prob isn’t the best way to do that or to convince fellow readers.

If you are unable to respond adequately to my challenges or no longer have time to devote then by all means withdraw from the debate - but you cannot expect to also have the last word if you make that choice. That’s a bit 'teenage" isn’t it, like wanting to have your cake and eat it too :blush:?

I have provided abundant texts and posts in this thread and more so in the other thread --from the Magisterium, Theologians, and even Catholic Answers (the site we are on…;)) Apologists …

Not going to continue going round and round.

Have a splendid rest of the Lords day!

Blue Horizon,

This is taking too much time (responding to all the multiple posts)

And I have provided texts in this thread and abundant texts and posts in the other thread (as have the other posters in the other thread)–from the Magisterium (Catechism, Compendium, Bl. Pope John Paul II, Pope Benedict XVI, Canon Law both east and west), Theologians (ie Fr. John Hardon -Catholic Dictionary and his Catechism), Moral Theology, etc and even from the organization that runs this site -the Catholic Answers Staff Apologists …

Not going to continue going round and round.

Have a splendid rest of the Lords day!

BookCat I have repeatedly challenged the readily observed weaknesses in your personal interpretation of these arguments from authority which render those quotes fairly inconclusive. (Some of your “authorities” above are themselves not particularly authoritative in this difficult area of moral theology).

Given these weaknesses you really need to show readers that the seeming illogical consequences of your position that I have demonstrated below are chimerical. To date you have not engaged so.

In summary the the sorts of consequent logical contradictions that your perfect identification of “grave sin” and “mortal sin” appear to lead to are:

  • “mortal sin” is also identical with its object (ie “grave matter”).
  • the object (ie matter) of sinful offences is also appropriately called “sin” (rather than “a disordered act”)
  • some “venial sins” can also be called “mortal sins”
  • confusion over exactly what the "objective nature of ‘mortal sin’ " refers to
  • an aversion to validly calling non-culpable transgressions of Natural Law (eg Incest or Prostitution) “sin” … or that such sins mean we may validly call this agent “a sinner” or “guilty” of sinning.
    If you are not prepared to seriously engage with unambiguous, clear and lucid counter-arguments (or you don’t have time) then let it go instead of obsessively trying to have the last authoritative word here.

To me the difference between grave and mortal sins is fairly clear:

Mortal sin is well defined in the Catechism. It is always **“a grave offence performed with deliberation (full consent and understanding)”. **Grave offences are described by the 10 Commandments.

Grave sin is not actually defined anywhere I can find.
It is a phrase that seems to have crept into moral theology over the ages.
However everbody appears to agree that it at least means “offences of grave matter.” Because degree of deliberation is rarely mentioned theologians tend to disagree over that bit.

Therefore, I maintain, that “Grave sins” can include three distinct types of offence:
(i) all fully deliberate offences of grave matter (mortal sins)
(ii) some partially deliberate offences (venial sins of grave matter)
(iii) fully non imputables offences (involuntary/unknown transgressions of the Commandments such as acts of prostitution, incest etc).

The above can get confused as both expressions have secondary meanings.
“Grave sin” sometimes is used to simply mean “a really bad deliberate offence”. In other words “grave sin” rather than the homogenous phrase “grave sin.
In this case “grave sin” is exactly the same as “mortal sin” as defined above.

Blue Horizon

It is all a “language question”. But it is important to note that the terms “grave sin” “mortal sin” “grevious sin” “serious sin” “deadly sin” are used in an interchangible way -though some terms will fit in differing sentences better than others (as is the case in other areas where language is concerned).

And they ALL can refer to:

  1. The objective nature of a sin in itself - such as where an intrinsically gravely evil thing is concerned (ie. Murder is a mortal sin, murder is a grave sin, murder is a serious sin, murder is a grevious sin …adultery is a grave sin, adultery is a mortal sin, adultery is a serious sin, adultery is a deadly sin etc). All meaning the same thing.

  2. The personal sin as committed. John is guilty of mortal sin, John is guilty of serious sin, John is guilty of grave sin, John is guilty of deadly sin…that is there was grave matter, full knowledge and deliberate consent. All meaning the same thing.

When I note “All meaning the same thing” -such is referring there to that they all “refer to the same subject”.

The differing terms do bring out different aspects of the thing of course -it is grave or grievous and serious instead “light or not serious” and it is mortal or deadly in that it is the kind of sin that brings about the death of the life of grace in the soul…as opposed to being not deadly …not mortal but venial.

(similar can be said for terms used for “venial sin”)

Mortal sin
Serious sin
Grave sin
Deadly sin
Grievous sin

Refers to:

  1. The nature “sin in itself”- independent of the culpability of the person. ie fornication is a mortal sin (grave sin, serious sin …etc.)

  2. The committed personal sin where there is not only grave matter but there is the needed full knowledge and the deliberate consent. ie Steve is guilty of fornication. Such sins are required to be confessed in confession.


Venial sin
Light sin
Daily sin
Non serious sin
Small sin

Refers to:

  1. Sins where the matter is light etc.

  2. When there was grave matter present but the full knowledge or deliberate consent was lacking but there was still sin committed.

They do not need to be confessed even if the matter itself was grave.

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