Sin is defined as an offense against God and reason, arising from a perverse attachment to certain goods that wounds human nature and injures solidarity (CCC 1849-1850). It is a manifestation of disobedience and revolt against the love of God, characterized as a love of oneself that reaches the point of contempt for God (CCC 1850). Furthermore, sin is contrary to God’s eternal law and the obedience of Christ (Rom 11:30-32), and it is fundamentally an abuse of the freedom given by God (CCC 387).

The origin of evil is a mystery that is only fully understood through divine revelation and the love of Christ (CCC 385). The root of sin lies in the free will of the creature, as seen in the case of the devil, a created angel who became evil by freely choosing to reject God and His reign (CCC 392). In human history, the root of sin is also found in human free will (Mt 15:19-20), manifesting in the primeval event of the fall of Adam and Eve (Genesis 3).

Original sin is a state of deprivation of original holiness and justice that was contracted through the fault of Adam (CCC 405). This condition is transmitted through propagation, affecting all of human nature and implicating all people in Adam’s sin, which led to condemnation and death (Rom 5:12-19, CCC 402-404). The consequences of this first sin include a distorted image of God, a breakdown in human relationships—specifically a rupture in the communion between man and woman characterized by domination and lust (CCC 400, 1608)—and the entry of death into human history (Genesis 3:19, CCC 401). Original sin wounds human nature, making it subject to ignorance and suffering, and creates a proclivity toward evil known as concupiscence (CCC 405, 2515).

Personal sins are categorized by their gravity and the nature of the offense. While all wrongdoing is considered sin, a distinction is made between mortal and venial sins (CCC 1853-1864). Mortal sin destroys charity, turns a person away from God, and results in eternal death if left unrepented; it requires grave matter, full knowledge, and deliberate consent (CCC 1854-1858). Venial sin offends and weakens charity but does not destroy it, remaining humanly reparable through God’s grace (CCC 1854-1863). Sins may also be classified by the objects they target, the virtues they oppose, or the commandments they violate, with capital sins—such as pride, avarice, and lust—being particularly pernicious because they generate other vices (CCC 1865-1866).

The theological significance of sin is seen in its destructive power, as the wages of sin is death (Rom 6:23). This condition places humanity in captivity under the power of the devil (CCC 407) and creates a persistent internal struggle between the spiritual law of God and the law of sin dwelling in the members of the body (Rom 7:14-25, CCC 409). Because of this fallen state, the human person is prone to sin due to a carnal nature, and the natural law becomes obscured, necessitating divine revelation to be fully understood (CCC 2071-2072).

Redemption from sin is made possible through the mission of Jesus Christ, who came to free humanity from sin (Jn 3:16-17). Through faith in Christ, individuals are freed from the bondage of sin to become slaves of righteousness (Rom 6:16-23). The sacrament of Baptism erases original sin and all personal sins, granting sanctifying grace (CCC 406, 1263). For sins committed after Baptism, the sacrament of Penance, or Reconciliation, is necessary to restore the sinner’s relationship with God (CCC 1422-1424, 1486). This process requires a conversion of heart involving repentance, confession, and contrition—either perfect, arising from the love of God, or imperfect (CCC 1490, 1492). The source of this forgiveness is the sacrifice of Christ in His Passion and the grace offered in the Eucharist (CCC 1846, 1851).