Vice is engendered through the repetition of sin, which corrupts the conscience and creates a proclivity to continue sinning (CCC 1865). Certain sins, known as capital sins—which include pride, avarice, envy, wrath, lust, gluttony, and sloth—are particularly pernicious because they give rise to other vices and sins (CCC 1866).

Sin is defined as an offense against God and humanity, caused by a perverse attachment to certain goods and a revolt against God’s love, often manifesting as a love of oneself to the point of contempt for God (CCC 1849-1850). All wrongdoing is considered sin (1 John 5:17), and it is an act of disobedience that wounds human nature and injures solidarity with others. The root of all sin lies in the human heart and free will, originating from evil thoughts (Mt 15:19-20).

The relationship between vice and sin is one of mutual reinforcement, as the repetition of sinful acts engenders vice, which then increases the inclination to sin (CCC 1865). This is further seen in carnal concupiscence, which is a movement of the sensitive appetite contrary to reason; while concupiscence is not an offense in itself, it inclines a person to commit sins (CCC 2515). Furthermore, there is a progression in the gravity of these acts, as venial sins, which weaken charity and impede spiritual progress, can lead to mortal sin if they are left unrepented (CCC 1863).

Sins are categorized by their gravity, with mortal sin destroying charity and turning a person away from God (CCC 1854-1855). For a sin to be mortal, it must meet three conditions: grave matter, full knowledge, and deliberate consent (CCC 1857-1861). In contrast, venial sin offends charity but does not destroy it (CCC 1854-1855), occurring when the moral law is not observed in a less serious matter or is disobeyed in a grave matter without full knowledge or complete consent (CCC 1862).

To remedy the disorders caused by sin and vice, the Church emphasizes the sacrament of Penance, specifically Confession to a priest, which is essential for reconciliation with God and the Church (CCC 1456, 1486). Regular confession of venial sins is strongly recommended to fight against evil tendencies and to form the conscience (CCC 1458). Additionally, the cultivation of human virtues, such as temperance—the virtue of restraining one’s appetites to maintain moral balance—is essential for living a godly life and protecting the integrity of love (CCC 1809-1810).