from the Council of Trent file…

In 1967, Pope St. Paul VI wrote:
The practice of indulgences has at times been improperly used either through untimely and superfluous indulgences, by which the power of the keys was humiliated and penitential satisfaction weakened, or through the collection of illicit profits by which indulgences were blasphemously defamed. (para. 8 of Indulgentiarum Doctrina)
In the 16th century: Lutheranism, Protestantism–the whole mighty conflict–began. And it began with: Indulgences.
During my Protestant youth, my good instructors in religion, including my dear mother and aunt, often repeated the story of the indulgence-preacher Johann Tetzel, who declared, “As soon as the coin in the coffer rings, the soul from purgatory springs.” Luther explicitly condemned that sentiment in his 95 theses.
Let’s try to sort this out.
God wills to befriend us for eternal life with Him. But that requires reconciliation with Him, with His pure goodness and holiness. Because we do not possess pure goodness and holiness.
Our reconciliation with God involves two dimensions:
1. Becoming God’s friend through Christ. Simple forgiveness of the eternal punishment we all deserve. The eternal punishment we all deserve = not being God’s friend forever. But, even though we don’t deserve His friendship, He offers it to us anyway.
2. Making up for all the bad effects of sin. Reparation. Doing penance. Serving a punishment that isn’t eternal. (Therefore, temporal.)

If we die lacking the first dimension of reconciliation with God, we wind up in… correct: Hell.
If we die having the first, but lacking the full term of the second aspect of reconciliation, we wind up in… you got it. Purgatory.
Now, only I, myself, me–responding freely and courageously in faith to the promptings of my conscience, by the grace of Christ–can avoid hell. I myself have to love God and regret my sins, in order to be a friend of God in Christ.
God forgives the penitent soul through the ministry of His Son’s Church. But the individual penitent soul must undergo that ministry. No one can go to confession on someone else’s behalf. No one can decide for someone else to love God and regret sin.
And no one will make a successful appeal on judgment day to someone else’s contrition for his sins. “My mom was sorry that I stopped writing her. She went to church a lot and prayed for me to get paroled. Isn’t that good, Big Guy?” Ah. No.
Hell awaits all unrepentant sinners who die.
But: When it comes to the second dimension of reconciliation with the perfect holiness of God–that is, a friend of God serving a just sentence for the bad effects of his or her sins–in that business, we can help each other.
In fact, in that business, the friends of God are all in it together. Christ our Head, and all His members, including our Lady and all the saints, share resources in order to overcome the effects of sin and achieve total honesty, total purity, total readiness to meet God face-to-face.
Obtaining an indulgence involves sharing in those resources, the “treasury” of the Holy Church, the holiness of Christ and His saints. Only a friend of God can receive an indulgence. And all of us friends of God need the help.
[Click HERE to read the full official Vatican handbook of indulgences. If offers very consoling reading.]