Catechism [1030-1032, 954-959]
We can die in the love of God but still deserve punishment for our sins just like a person can steal something, be sorry, but still deserve punishment. This punishment we deserve might be called the “stains of sin.” Such stains are cleansed away in a purifying process called purgatory. These stains of sin are primarily the temporal punishment due to venial or mortal sins already forgiven but for which sufficient penance was not done during your lifetime. This doctrine of purgatory, reflected in Scripture and developed in Tradition, was clearly expressed in the Second Council of Lyons (A.D. 1274).
Having passed through purgatory, you will be utterly unselfish, capable of perfect love. Your selfish ego-that part of you that restlessly sought self-satisfaction-will have died forever. The “new you” will be your same inner self, transformed and purified by the intensity of God’s love for you.
Besides declaring the fact of purgatory, the Second Council of Lyons also affirmed that “the faithful on earth can be of great help” to persons undergoing purgatory by offering for them “the sacrifice of the Mass, prayers, almsgiving, and other religious deeds” (63)
A Redemptorist Pastoral Publication. Handbook for Today’s Catholic . 4th ed. Liguori : Liguori Publications, 2004; May 19, 2009.



