From the Catechism
SIN
I. Mercy and Sin
1846 The Gospel is the revelation in Jesus Christ of God's mercy to sinners.113 The angel announced to Joseph: "You shall call his name Jesus, for he will save his people from their sins."114 The same is true of the Eucharist, the sacrament of redemption: "This is my blood of the covenant, which is poured out for many for the forgiveness of sins."115
1847 "God created us without us: but he did not will to save us without us."116 To receive his mercy, we must admit our faults. "If we say we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, he is faithful and just, and will forgive our sins and cleanse us from all unrighteousness."117
1848 As St. Paul affirms, "Where sin increased, grace abounded all the more."118 But to do its work grace must uncover sin so as to convert our hearts and bestow on us "righteousness to eternal life through Jesus Christ ourLord."119 Like a physician who probes the wound before treating it, God, by his Word and by his Spirit, casts a living light on sin:
Conversion requires convincing of sin; it includes the interior judgment of conscience, and this, being a proof of the action of the Spirit of truth in man's inmost being, becomes at the same time the start of a new grant of grace and love: "Receive the Holy Spirit." Thus in this "convincing concerning sin" we discover a double gift: the gift of the truth of conscience and the gift of the certainty of redemption. the Spirit of truth is the Consoler.120
113 Cf. ⇒ Lk 15.
114 ⇒ Mt 1:21.
115 ⇒ Mt 26:28.
116 St. Augustine, Sermo 169, 11, 13: PL 38, 923.
117 1 Jn 8-9.
118 ⇒ Rom 5:20.
119 ⇒ Rom 5:21.
120 John Paul II, DeV 31 # 2.
1848 As St. Paul affirms, "Where sin increased, grace abounded all the more."118 But to do its work grace must uncover sin so as to convert our hearts and bestow on us "righteousness to eternal life through Jesus Christ our Lord."119 Like a physician who probes the wound before treating it, God, by his Word and by his Spirit, casts a living light on sin:
Thanks for the Catechism. Correct me if I'm wrong, but I interpret this to necessarily mean mortal sins at a minimum (confessing required, etc.). That would mean that mortal sin is inevitable from original sin, which is what I thought the Catholic position was. But before I get ahead of myself ......... :)