Temporal Punishment and Suffering
Sin has two consequences, or punishments (CCC 1472). The first is eternal punishment, in which the soul loses heaven and is confined to an eternity in hell. This punishment is remitted through the forgiveness of sins. The second is temporal punishment, in which a person must expiate, or make reparation for his sins. This temporal punishment remains even after sin is forgiven. Some examples include Adam and Eve getting thrown out of Paradise when they ate the forbidden fruit (Genesis), and the Israelites losing the privilege of seeing the Promised Land because they worshiped the golden bull (Exodus). Unlike eternal punishment, temporal punishment remains only for the period of time it takes for the expiation of one's sins. Temporal punishment is God's method of loving discipline: "Do not disdain the discipline of the Lord . . . for whom the Lord loves, he disciplines; he scourges every son he receives" (Heb. 12:5).
How does one expiate his sins? The Catholic Church has traditionally identified three major ways–prayer, fasting, and almsgiving. Any good work or sacrifice expiates sin, as well as patiently bearing our sufferings and offering them up in satisfaction for our sins (CCC 1459-1460). We may also take it upon ourselves to do voluntary penance. Some saints have done austere penances in satisfaction for their sins, such as sleeping on bare boards, dressing scantily in cold weather, self-flagellation, and wearing a hairshirt or a necklace made of jagged items to irritate the skin. Although efficacious, most Christians should strive to follow the penitential spirit of the saints while performing penances suitable to them.
There is one more method of expiation, and that is the gaining of indulgences. An indulgence is the remission of temporal punishment due to sins already forgiven (CCC 1471). The merits gained by Christ was enough to expiate all sins, and these merits, combined with the merits of Mary and the saints that were in excess of what they needed, form the Spiritual Treasury of the Church (CCC 1476). It is from this treasury that the Church grants indulgences for the remission of temporal punishment, when a certain prayer or work is performed. A plenary indulgence (ie. The Stations of the Cross) remits all of one's punishment, while a partial indulgence (ie. reading Scripture or 15 minutes) remits a portion of one's punishment. A certain number of days and years used to be attached to partial indulgences, but this was changed due to the confusion it caused. Indulgences may be gained for one's self, or may be applied to the souls in purgatory. To gain an indulgence, one must have at least a general intention of gaining the indulgence, be in the state of grace, and perform the work. To gain a plenary indulgence, which can only be gained once per day, one must also confess eight days before or after the work is performed, receive communion on the day of the work, pray an Our Father and a Hail Mary for the pope's intentions, and have no attachment to (intention to commit) any sin, even venial sin.
What happens if one has not fully expiated his sins before dying? Such a person, before going to heaven, would have to expiate his sins in purgatory (CCC 1030), where love for God is perfected through our sufferings there. Traditionally, the sufferings of purgatory have been compared to a "consuming fire" (1 Cor. 3:11-15). Because certain sins can be forgiven "in the age to come" (Matt. 12:32), Catholics have always prayed for the dead–for the relief of their souls, or their speedy deliverance, if they are in purgatory, for "it is a holy and wholesome thought to pray for the dead, that they may be loosed from their sins" (2 Macc. 12:46).
Our sufferings, according to St. Paul, "make up for what is lacking in the sufferings of Christ" (Col. 1:24). Interpreted properly, this means that our sufferings can be offered up for any intentions and act just like a prayer. When we do this, God pours out His grace (as He does through all our prayers) and our sufferings become redemptive. Because of this, we should patiently bear our sufferings and "offer them up".