What an indulgence is
The Catechism defines it (CCC 1471): an indulgence is a remission before God of the temporal punishment due to sins whose guilt has already been forgiven. The faithful who are properly disposed can gain it under certain defined conditions, through the Church's help, as she dispenses and applies the treasury of the merits of Christ and the saints.
Take that apart. We've seen that sin has two consequences: the guilt, and the lingering effects that need healing. Confession removes the guilt. An indulgence addresses the second thing, the temporal punishment. It doesn't forgive sin, and it doesn't give grace. It's a way the Church, drawing on the merits of Christ and the saints, helps heal what forgiveness has left unfinished.
What it is not
An indulgence isn't a license to sin. It isn't a purchase. It isn't a ticket out of Purgatory, and it doesn't guarantee a particular outcome. The Council of Trent condemned the abuse of money in connection with indulgences, and in 1967 Pope Paul VI reformed their discipline and removed the old numbers of days and years that had misled people. Today the Church says plainly that indulgences are to be sought with the right interior dispositions, and that they depend on the person's conversion of heart.
Partial and plenary
An indulgence is either partial or plenary. A partial indulgence removes part of the temporal punishment, and a plenary indulgence removes all of it. For the person gaining it, a plenary indulgence requires being completely free of any attachment to sin, even venial sin, which is why it's rarely gained in its fullness. The Church's wording is cautious here. If the person lacks this disposition, the indulgence is only partial.
The usual conditions
The usual conditions for a plenary indulgence are these: sacramental confession (within about twenty days before or after), Holy Communion, prayer for the intentions of the Holy Father, and the interior disposition of being free from all attachment to sin. The work specified must be done too, whether that's a prayer, a pilgrimage or a visit. Normally, one plenary indulgence can be gained per day.
Applying them to the dead
This is where indulgences matter for our subject. The Church allows an indulgence to be offered for a soul in Purgatory, but only "by way of suffrage," which means as a prayer to God asking Him to apply it, not as something that takes effect automatically. We can't gain an indulgence for another living person, but we can offer one for the dead. And we can't be certain how God will apply it. The Church teaches that it's a real help, and she leaves the result with Him.
November and All Souls' Day
The Church offers special indulgences for the dead around All Souls' Day. A plenary indulgence, applicable only to the souls in Purgatory, can be gained by those who devoutly visit a cemetery and pray, even mentally, for the departed on each day from November 1 to 8. On November 2 itself, a plenary indulgence is available for those who visit a church or oratory and say the Our Father and the Creed. At other times of the year, a visit to a cemetery with prayer for the dead gains a partial indulgence.
It's worth noting that the exact norms are set by the Apostolic Penitentiary and can change, so please check the current instructions each year, or ask your parish priest, before you rely on any dates or conditions.
Avoiding the transaction mindset
The best protection against superstition is to remember what an indulgence is for. It isn't a way of saving time. It's a way of loving someone. The heart of every indulgence is an act of love: a prayer, a visit to a grave, a gift to the poor, a sacrifice offered. If you find yourself counting and calculating, it's a sign to return to the simple center, which is prayer for someone you love.
.
