Catechism of the Catholic Church

1849 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." ¹²¹

1850 Sin is an offense against God: "Against you, you alone, have I sinned, and done that which is evil in your sight." ¹²² Sin sets itself against God's love for us and turns our hearts away from it. Like the first sin, it is disobedience, a revolt against God through the will to become "like gods," ¹²³ knowing and determining good and evil. Sin is thus "love of oneself even to contempt of God." ¹²⁴ In this proud self- exaltation, sin is diametrically opposed to the obedience of Jesus, which achieves our salvation. ¹²⁵

1851 It is precisely in the Passion, when the mercy of Christ is about to vanquish it, that sin most clearly manifests its violence and its many forms: unbelief, murderous hatred, shunning and mockery by the leaders and the people, Pilate's cowardice and the cruelty of the soldiers, Judas' betrayal - so bitter to Jesus, Peter's denial and the disciples' flight. However, at the very hour of darkness, the hour of the prince of this world, ¹²⁶ the sacrifice of Christ secretly becomes the source from which the forgiveness of our sins will pour forth inexhaustibly.