Catechism of the Catholic Church
388 With the progress of Revelation, the reality of sin is also illuminated. Although to some extent the People of God in the Old Testament had tried to understand the pathos of the human condition in the light of the history of the fall narrated in Genesis, they could not grasp this story's ultimate meaning, which is revealed only in the light of the death and Resurrection of Jesus Christ. 261 We must know Christ as the source of grace in order to know Adam as the source of sin. The Spirit-Paraclete, sent by the risen Christ, came to "convict the world concerning sin", 262 by revealing him who is its Redeemer.
389 The doctrine of original sin is, so to speak, the "reverse side" of the Good News that Jesus is the Saviour of all men, that all need salvation and that salvation is offered to all through Christ. The Church, which has the mind of Christ, 263 knows very well that we cannot tamper with the revelation of original sin without undermining the mystery of Christ.
English Translation of the Cathechism of the Catholic Church for the United States of America © 1997, United States Catholic Conference, Inc.