To put it shortly, every time you go to Confession the priest gives you a penance.
This penance is
only a partial penance for the sins you committed. While the guilt is forgiven, the penance due to sin
is not forgiven by Confession. Every sin has penance due it by God’s justice.
If we do not do the penance in this life
we do it in the next. This is Purgatory.
There are two effects of sin Purgatory is said to address: First of all the interior changes needed within a person to enter Heaven, and Second the penance due God’s Justice for the sin.
In this life we are called by the Church to do penance for our sins. The Church’s indulgences are the giving of the merits of Christ and of the saints towards our penances.
It is through the power of St. Peter’s keys and the authority to bind and loose sin that indulgences are given.
What are the merits of the saints? To understand this you must understand merit. I will not explain that here unless you need to know, it is also basic Catholicism that often is not taught however.
As Christians we are called to gather as much merit as we can in this life so that our place in Heaven is the high point it should be, rather than less than it should be. Those with merit are the first in the kingdom of Heaven, those without are the last. We can only acquire it in a state of grace, as too our prayers are only obliged to be heard in, and indulgences given.
Since spiritual indulgences require right intention to be received, it is impossible to buy them, and so this never actually occurred despite the accusations.
Indulgences are the Church’s application of Christ’s and the saints’ merits to our own penances, and she ‘indulges’ certain acts and penances so that these merits are authoritatively joined with ours in the Communion of Saints.
Thereby we may through indulgences:
- Lessen our time of penance in Purgatory, to eliminate it.
- Lessen others time of penance in Purgatory, to eliminate it.
So they are a large part of the charitable devotion to relieve the suffering souls in Purgatory.
There is a small Handbook on Indulgences which lists some of them one can purchase and make use of.
To gain an indulgence it is necessary to: A. Be in a state of grace. B. Perform the indulgenced act, according to whatever requirements it has, and C. Intend to gain the indulgence.
I have heard it said it is sufficient at the start of the day to say a short prayer with the intention of gaining all the indulgences applicable to one’s acts that day, to gain them generally for that day but I would keep the intention in mind fresh.
If I’ve made any mistake about what I have said here please correct me or fill in the blanks.
