For most Christians today, indulgences represent darker days in the history of the Church. For Protestants, the Church’s practice of granting indulgences is seen as a real deathblow to Catholicism—indisputable evidence that the Catholic faith cannot be true. For Catholics—many of them devout and well-meaning—indulgences are a thing of the past and “thankfully” no longer a part of the Church’s teaching.
However, both of these sets of Christians are mistaken. Indulgences are still (and always will be) a part of the Catholic Church's infallible teaching. And they constitute a real gift—an astoundingly beautiful and wonderful blessing—in the life of the Church. But to understand why indulgences represent a blessing, rather than an embarrassment, for the Catholic Church, we must first understand what an indulgence actually is.
According to the Catechism of the Catholic Church,
“[a]n indulgence 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” (1471).
To put this into layman's terms, we would say that an indulgence is simply what we receive when the Church, through Her power to bind and loose (Mt. 16:19, 18:17-18), lessens the temporal punishment we face as a result of our sins, even after they have been forgiven.
Let’s unpack this. Scripture shows us that the punishment we receive for our sins can be both eternal (i.e. hell) and temporal (i.e. here on this earth). For example, when Adam and Eve sinned, the temporal punishments that they each respectively received were the toiling over the land and the intensifying of childbearing pains (Gen. 3:16-19). But what is interesting, for the purposes of our discussion on indulgences, is that Scripture also tells us that, even after our sins have been forgiven, the temporal punishments we face as consequence of them often remain. For example, when the prophet Nathan confronts King David about the king's adultery, Nathan tells him, "The Lord on His part has forgiven your sin; you shall not die. But since you have utterly spurned the Lord by this deed, the child born to you must surely die" (2 Sam. 12:13-14). Another example is in Numbers, where we read, "Then the Lord said, 'I have pardoned them, according to your word; but truly as I live...none of the men who...have not hearkened to my voice, shall see the land which I swore to their fathers" (Num. 14:20-23). Even death itself is a temporal punishment of the sin of Adam and Eve, which is a punishment that we still bear today, despite the forgiveness of sins we receive from Jesus.
So, the Bible teaches us that the temporal punishment we receive for our sins often remains even after we repent and are given the forgiveness of God. And an indulgence is a grant from the Church that reduces this punishment.
How does the Church do this, and does She even have the authority to do so?
Throughout Scripture, we see that God blesses some people as a reward to others. For example, consider how Jesus heals a daughter, as a result of her mother's faith (Mt. 15:21-28). And sometimes, when God blesses a person as a reward to another, this blessing takes the form of a reduction of the temporal punishment to which the first person is subject. As an example of this, we might look at 1 Kings 11:11-13, which reads,
"The Lord said to Solomon, 'Since this is what you want, and you have not kept my covenant and my statutes which I enjoined on you, I will deprive you of the kingdom and give it to your servant. I will not do this during your lifetime, however, for the sake of your father David; it is your son I will deprive. Nor will I take away the whole kingdom. I will leave your son one tribe for the sake of my servant David and of Jerusalem, which I have chosen."
So, God delays and reduces the temporal punishment due to Solomon, not because of Solomon’s own merits and piety, but as a result of the holy life of his father, David.
All of this provides the context necessary for understanding what an indulgence is and how they work. The Catholic Church recognizes that the pious and charitable acts of Jesus, Mary, and the saints—whether the saints in heaven or those on earth—can please God so as to shorten the temporal punishment of other Christians. Therefore, the Church, through Her authority to bind and loose (Mt. 16:19, 18:17-18), is able to “open…the treasury of the merits of Christ and the saints” (CCC 1478), and “dispense and appl[y] with authority th[is] treasury of satisfactions” (CCC 1471) to a forgiven and repentant sinner, and does so by granting such sinner an indulgence. However, the Church, in an effort “not…simply to come to the aid of [individual] Christians, but also to spur them to works of devotion, penance, and charity” (CCC 1478), only grants indulgences under limited circumstances. For example, an indulgence might be granted when a forgiven sinner strives to please God through the pious act of going to Confession and praying for the intentions of the Pope, or through the charitable act of tithing or donating money for the construction of a hospital or church.
The fact that the Catholic Church grants indulgences in recognition for the charitable act of tithing, in large part, explains why so many, both in the past and present, mistakenly believe that the Church “sells” indulgences. But, to reiterate what has already been said, indulgences are granted in these instances not in exchange for money, but in recognition for the faith and piety displayed in charitably giving away one’s financial means.
It is true that, in the time of Martin Luther, there were priests who misunderstood the official teaching of the Church on indulgences as they apply to the souls in Purgatory. However, the official teaching of the Church--before Luther, during Luther, and after Luther--has never permitted the selling of indulgences. Any priest who might have gone rogue and preached otherwise was in direct contradiction with the Church. 
The practice of granting indulgences is a long-standing practice of the Catholic Church, and, as noted before, is one She exercises through Her God-given power to bind and loose. Through an indulgence, a repentant sinner is (1) encouraged to take further action to make amends for his forgiven sins; (2) is able to “supercharge”—in a manner of speaking—these acts by coupling or uniting them with other holy actions performed by Jesus and the saints throughout history; and (3) receives the assurance of the Church that he has pleased God in taking these actions. So, let us celebrate and take full advantage of this incredible gift made available to us in the Church, rather than attempting to sweep it under the rug, as if it were some sort of embarrassing vestige of our Church’s past.
 Much of the abuse of the doctrine of indulgences is today attributed to the now infamous Dominican, Johann Tetzel. Contrary to many of the exaggerated and even unfounded accusations made against Tetzel today, many historians now agree that he was a man of real moral integrity. But it is nonetheless true that the friar preached his personal, but mistaken belief about indulgences as they apply to souls in Purgatory. To be more specific, although it is absolutely true that we can gain indulgences that benefit or apply to souls in Purgatory (as, again, God blesses some as a reward to others), Tetzel mistakenly believed that this meant that the earthly soul did not actually have a contrite heart, but instead only needed to perform external acts of piety, in order to receive an indulgence in this particular situation. In other words, for Tetzel, because the earthly soul was not benefiting from the indulgence, but was instead offering the indulgence up to be applied to another, he thought that the subjective state of the earthly soul was irrelevant in these scenarios. But, even though a handful of priests like Tetzel might have proclaimed this false doctrine, it is also true that Catholic authority figures, like Cardinal Cajetan, publicly rejected and condemned this false position, as late as 1517-19.
Daniel Box lives in Chicago with his wife, but is a proud Texan (Fort Worth native) and Mexican-American. He is a practicing real estate and zoning attorney, after having clerked with the Thomas More Society and served as the Board Chairman of the Chicago chapter of Young Catholic Professionals in 2015 and 2016. He received his Bachelor of Arts degree in Politics from the University of Dallas in 2012.