In the Cathecism of the Catholic Church, Part Three Life in Christ, Section One Man’s Vocation Life in the Spirit, Chapter One The Dignity of the Human Person, Article 8 Sin, the Church teaches us that:
- “Sin is an offense against reason, truth, and right conscience; it is failure in genuine love for God and neighbor caused by a perverse attachment to certain goods. It wounds the nature of man and injures human solidarity. It has been defined as “an utterance, a deed, or a desire contrary to the eternal law.” (See 1849) In other words, “sin is an offense against God” (See 1850).
The Catechism also teaches us that there are many kinds of sin (see 1852), and that sins can be distinguished according to their objects, as can every human act; or according to the virtues they oppose, by excess or defect; or according to the commandments they violate (see 1853). Finally, the Catechism teaches us that sins are rightly evaluated according to their gravity (see 1854).
- Mortal sin destroys charity in the heart of man by a grave violation of God’s law; it turns man away from God, who is his ultimate end and his beatitude, by preferring an inferior good to him, and
- Venial sin allows charity to subsist, even though it offends and wounds it (see 1855).
However, for a sin to be mortal, three conditions must together be met: “Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent.” (see 1857 and 1860).
- The sin must involve a grave matter;
- The person who sins must have knowledge of the sinful character of the act, of its opposition to God’s law; and,
- The person must give full knowledge and complete consent to be a deliberate personal choice (see 1859).
A 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. (see 1858).
One question we might have is whether or not a sin involving an intrinsic evil is “automatically” a mortal sin? Is it always a grave matter? Well, take for instance a lie. A lie is an intrinsic evil. It is always wrong not matter what the circumstances are. However, it is not necessarily a mortal sin.
- The Catechism states that “lying is the most direct offense against the truth. … By injuring man’s relation to truth and to his neighbor, a lie offends against the fundamental relation of man and of his word to the Lord…” (see 2483)
- The Catechism also states that by its very nature, lying “…is to be condemned. … The culpability is greater when the intention of deceiving entails the risk of deadly consequences for those who are led astray…” (see 2485).
- Further, the Catechism states that lying “…is destructive of society; it undermines trust among men and tears apart the fabric of social relationships…” (see 2486).
- The Lord denounces lying as the work of the devil: “You are of your father the devil, . . . there is no truth in him. When he lies, he speaks according to his own nature, for he is a liar and the father of lies.” (see 2482)
So, lying is an instrinsic evil. However, it is not automatically a grave matter or a mortal sin. However, one can see that when a lie is “…made publicly, a statement contrary to the truth takes on a particular gravity. In court it becomes false witness. When it is under oath, it is perjury. Acts such as these contribute to condemnation of the innocent, exoneration of the guilty, or the increased punishment of the accused. They gravely compromise the exercise of justice and the fairness of judicial decisions” (see 2476).
- 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 (see 2484).
- However, we must remember that a good intention (for example, that of helping one’s neighbor) does not make behavior that is intrinsically disordered, such as lying and calumny, good or just. The end does not justify the means. Thus the condemnation of an innocent person cannot be justified as a legitimate means of saving the nation …” (see 1753).
Reference: See the Catechism of the Catholic Church, Part Three: Life in Christ, Section Two The Ten Commandments, Chapter Two You Shall Love Your Neighbor As Yourself, Article 8 The Eighth Commandment, III. Offenses Against Truth