Catechism of the Catholic Church
Para. 1857: 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" (RP 17 § 12).
Para. 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" (Mk 10:19). 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.
Para 1859: Mortal sin requires full knowledge and complete consent. It presupposes knowledge of the sinful character of the act, of its opposition to God's law. It also implies a consent sufficiently deliberate to be a personal choice. Feigned ignorance and hardness of heart (Cf. Mk 3:5-6; Lk 16:19-31) do not diminish, but rather increase, the voluntary character of a sin.
NCCB/USCC Home Page
Office for the Catechism Home Page
General Info
Ad Hoc Committee
Cat Update
Q & A
Articles
Editions
Documents