Lying - always mortal sin?

My cousin had informed me that if you think about lying before you even say the lie, that it is a mortal sin. Or, she might have said if you think that it’s wrong right before you lie, and than you say the lie afterwards. Not exactly sure, but is this true??? I normally never like to lie, but I have said little white lies, one recently was lying about my age by year. I don’t know if this would be considered mortal or not, but now that my cousin told me this, I feel like even if I say the smallest lie that I would be in mortal sin. So, my question is… is lying always a mortal sin?

Often it is a venial sin.

(still sin and thus to be avoided)

Examples of mortal sin would be lying under oath in court (which is worse even --being perjury) Or say lying in some other serious way.


2484 The gravity of a lie is measured against the nature of the truth it deforms, the circumstances, the intentions of the one who lies, and the harm suffered by its victims. If a lie in itself only constitutes a venial sin, it becomes mortal when it does grave injury to the virtues of justice and charity.

Go to the source (the catechism) for the truth, not your cousin

Lying to get out of a minor inconvenience is a venial sin.
Lying under oath is a grave sin as that is perjury.
Lying even if not under oath but damages a person’s reputation is a grave sin.

May I ask what you mean by lying that damages a person’s reputation? So, would that fall under the same category as gossiping?

Let’s say you stole, say a small amount (5 dollars or so) from the till at which you work. That in itself is probably a venial sin if it’s really small relative to the overall profitability of the company. But let’s say, there’s a zero-tolerance policy towards stealing, so anyone caught stealing gets fired.

To protect yourself, you lie about it and your coworker gets fired. Now you’ve cost your coworker a job and probably damaged her reputation such that she couldn’t easily get a recommendation and damaged her employment prospects. That’s a mortal sin.

I don’t think it’s a sin at all to lie about some things. For example: “oh no, you don’t look fat in that dress” or “yeah, I do like the gift you gave me.”

Nothing wrong with those. :slight_smile:

Lying is mortal relative to the harm/offense it causes. Thus,

to God:
If one commits perjury, one has lied to God. (Very serious, irreverent, profane)
If one lies in the confessional, about a serious sin, that is also a lie made to God, and is sacrilege.

to Neighbor:
If one’s lies harm a person’s good name (such as with calumny or even speculatively through persistent gossip), that is very serious.

to an Institution:
If the lie involves or results in fraud, or a misrepresentation which has consequences to a number of people, that can be very serious. (such as, to an arm of the gov’t, or to an educational institution). An example would be a student or professor claiming authorship of someone else’s work or research, IOW, plagiarism; if that submission resulted in an honor or prize unjustly granted, that would intensify the gravity of the lie)

to an Employer:
If one’s lies result in significant illegitimate gain (such as an unearned promotion of oneself or an unjust usurption of someone else’s job), that would be serious.

Those are just examples, of course. You have to consider:
The content of the lie (light or heavy)
Object of the lie (position or importance of the hearer)
Personal motivation for the lie
Involvement of any others in the lie – such as using one’s own residential address as a favor for someone seeking dishonest privileges in your county, city, school district, etc.
Known or likely consequences of the lie

Little lies to save face, while very indicative of the sin of pride, are the kinds of lies most people make. They are indeed sinful because they violate truth, even when they do not violate justice, but there are so many committed in this category that they usually overshadow in quantity the more serious ones, above.

Tis a sin. A venial sin but a sin none the less.

Unless there is some legit mental reservation.

Small sins are still sins (even those we think are “doing someone a favor”). We need to seek to avoid them.

Fr Pacwa stated on his program once like this.

A lady called in explaining that an elderly lady baked her a cake. The cake was missing something and tasted rather badly. The elderly lady a couple of days later asked how she like the cake? Instead of telling her it was awful and hurting her feelings or lying and saying it was good, you could thank her for the cake and tell her you really enjoyed her making it for you.

It is not lying by saying you enjoyed the thought behind the good deed.



2489 Charity and respect for the truth should dictate the response to every request for information or communication. **The good **and safety of others, respect for privacy, and the common good are sufficient reasons for being silent about what ought not be known or for making use of a discreet language. The duty to avoid scandal often commands strict discretion. No one is bound to reveal the truth to someone who does not have the right to know it.283 (website for Catechism

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