What Is An Indulgence
God is infinitely just and infinitely merciful. For us justice and mercy are usually a compromise. If we are just, in the strictest sense, we may not be merciful. And, if we are merciful, beyond the requirements of personal responsibility, we may not be just. But, for God justice and mercy are not in opposition.
When we approach the Sacrament of Penance, certain requirements must be present before sins can be forgiven.
This last requirement, the requirement for reparation, is where indulgences come into play. God in His infinite Mercy knows we cannot repair the full damage of our sins. Only Jesus, in His Sacrifice on the Cross, can make a full retribution to God's Justice. He pays the price for what we cannot repair, and an indulgence frees us from the burden and restores us fully in His Grace.
Perhaps and example will clarify this point.
"A boy playing ball breaks a window of his home. Contrite and sorrowful he goes to his father, who forgives him. However, despite the forgiveness the window is still broken and must be repaired. Since the boy's personal resources are insufficient to pay for a new window, the father requires him to pay a few dollars from his savings and forego some of his allowance for several weeks, but that he, the father, will pay the rest." 2
"This balances justice and mercy. To ask the boy to do nothing, when it is possible for him to make some reparation, would not be in accordance with the truth, or even the boy's good. Yet, even this temporal debt is beyond the boy's possibilities."3
"Therefore, from his own treasury the father generously makes up what the child cannot provide. This is [the nature of an] indulgence. Catholic teaching respects the natural order of justice, as Jesus clearly did in the Gospels, yet [Our Lord and His Church] recognizes that man cannot foresee or undo all the temporal consequences of his sin. However, God in His mercy will satisfy justice for what we cannot repair." 4 He will pay what we cannot.
"So, while sacramental absolution forgives the eternal guilt of sin, which requires the infinite merits of Christ, it does not necessarily remove all the temporal punishment, since they are somewhat within our power to repair (and somewhat unknown to us)…"5
An indulgence, therefore, takes our expiation, in the form of a specified prayer, penance, act of charity or other designated work, and adds to its intrinsic merit before God an additional value based on the treasury of merits of Jesus Christ, and those perfectly united to Him in heaven (the saints).
"Performing an indulgenced work should have the consequence of fixing our will away from our sins and entirely on God. This is why among the most important of the conditions for receiving a plenary indulgence, and the hardest to satisfy, is the complete detachment or detestation of our sins. By detesting our sins we orient our will away from creatures (to the degree we love them inordinately), towards God. In this way we open our will to the action of His mercy flowing into our souls, which alone is able to effect the complete remission of the temporal punishment to our sins."3
An indulgence is an action of the Church which spreads her treasure of merits to the suffering members of the family of God.
It is "a remission before God of the temporal punishment due to sins whose guilt has already been forgiven, which the faithful Christian who is duly disposed gains under certain prescribed conditions through the action of the Church which, as the minister of redemption, dispenses and applies with authority the treasury of the satisfactions of Christ and the saints.”6