The Catholic doctrines concerning purgatory and indulgences are based upon the Catholic doctrines of sin, penance, and the solidarity of the Mystical Body of our Lord Jesus. In other words, purgatory and indulgences have their place in Catholic moral life, because they are tightly tied into the sacramental ordering of life by the sacraments of penance and the anointing of the sick. Both doctrines—on purgatory and indulgences—are often misunderstood.35
Many people imagine that indulgences are remissions of sin. They are not. On the contrary, indulgences are of no use whatever unless sin itself has been repented and forgiven. Many people think of purgatory as a kind of short-term hell, suited to those who are sinners but not great enough sinners to be damned forever. On the contrary, purgatory is an initial stage of heavenly glory, suited to those who are saints but who need a moment to adjust their garments—that is, the good deeds in which they are dressed—before making their entrance into the wedding banquet which lasts forever.
Basic to both doctrines is the idea of temporal punishment. Once sin itself has been overcome by repentance and reconciliation, there remain existential effects of sin. These effects are taken care of by penance, provided one has a sufficient opportunity to do penance and does it. If one fails to do sufficient penance in this life, the rectification still necessary is somehow accomplished after death, in ways only God knows. This rectification after death is purgatory (see DS 1304/693, 1580/840, 1820/983).
Someone who dies in friendship with God is in a position utterly diverse from that of someone who dies at enmity with him. Even if some rectification is required, one who dies in friendship with God is welcomed into the kingdom. If some purification is needed, it is like the process of healing, not like the void of death (see S.c.g., 4, 91). Therefore, purgatory is altogether diverse from hell, and the tendency to assimilate the two states is mistaken.
Still, some who die and many who live can use help in satisfying for sins. All the penance we can do either is not enough or would be too arduous for us. At this point, the solidarity of the Church comes to the rescue. Having been redeemed by being united with Jesus, our satisfaction for sin also can be achieved by his help and by the help of Mary and the other saints. By the will of Jesus, the Church, which has the power to make effective in heaven what it does on earth (that is, the power of binding and loosing), simply extends to the repentant sinner in need of help in penance the help abundantly present in the merits of Jesus and the saints. This extending of help is an indulgence.
Thus, indulgences are remissions of punishment, not absolutions of sin. They are an act by which Jesus in the Church, having forgiven sin, also takes away all or part of the moral consequences of one’s having sinned (see S.t., sup., q. 25, a. 1; q. 27, a. 1). The effect of the system of indulgences is that either the sacrament of penance or anointing together with a plenary (full) indulgence puts one in much the same position as a newly baptized person or one who died immediately after baptism without having committed any sin whatsoever.
The doctrine of purgatory reveals the importance of the penitential dimension of Christian life. The granting of indulgences makes it clear that this dimension need not and should not be onerous. Only sin is ultimately evil, and penance is not sin. It is an important aspect of unity with Jesus, who though sinless paid for sin.