An indulgence is a remission of the temporal punishment due to sins whose guilt has already been forgiven, which the faithful Christian gains under certain prescribed conditions through the action of the Church.
Sin has two consequences: guilt and punishment. Punishment can be eternal or temporal. When God forgives sins, he removes the guilt and the eternal punishment, but the temporal punishment may remain. An indulgence removes this temporal punishment. Therefore, an indulgence is called partial or plenary according as it removes either part or all of the temporal punishment due to sin. The distinction between eternal and temporal punishment is evident in connection with Original Sin. When it is forgiven a temporal punishment remains. We will all die.
It is the essence of the doctrine of indulgences that Jesus in his mercy uses the Church he founded to forgive sins and to remove the temporal penalties due sins. The biblical basis for this teaching is found in the power Jesus promised his Church through Peter and his Successors "I will give you the keys of the kingdom of heaven, and whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven" (Mt 16:19)
The traditional opposition to indulgences at the time of the Reformation came from the abuse of indulgences that bordered on superstition, and from the evil practice of selling indulgences. Today that opposition is rooted in the rejection of the Church's authority, and defective notions of justification that has God doing everything and humans doing nothing.
The purpose of granting indulgences is to spur Christians to perform "works of devotion, penance, and charity." (CCC 1478) In this way the Church brings God's mercy to sinners in another way, as she encourages her members to pray for the dead and to offer prayers and penances for them.
The most common forms of penance are prayers, fasting, and almsgiving. These three pious acts diminish or eliminate pride, disordered appetites, and excessive attachment to and desire for things. Jesus recommended prayer, fasting, and almsgiving during the Sermon on the Mount.
To gain a plenary indulgence, a person must receive the sacraments of confession and the Eucharist seven days before or after performing the indulgenced work. The person must pray for the intention of the Pope. The customary prayers include one Our Father, one Hail Mary, and one Glory Be. Finally, the person must be free from any attachment to sin, even venial sin. If any of these conditions are absent, the indulgence will be partial.
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