On ARTICLE 10 of the Catechism of the Catholic Church (CCC) - I Believe in the Forgiveness of Sins, II. The Power of the Keys, CCC 981-83, 86-87; submitted November 3, 2017.
“[The Church] has received the keys of the Kingdom of heaven so that, in her, sins may be forgiven through Christ’s blood and the Holy Spirit’s action.” This is perhaps the most important argument for the legitimacy of the Church and the divine license by which she operates. All at once, Saint Augustine affirms the long-held Tradition of the Church’s apostolic succession, the forgiving authority she holds, and teaching office she alone maintains, by describing—in a two-fold sense: literally and symbolically—the nature of the relationship between the Catholic Church and God. More specifically, however, Augustine reminds us that this office, first given to Peter, serves as the means by which sins are forgiven in life. The permanency, efficacy, and importance of this divine authority cannot be understated. After all, Christ himself warns, or at least informs us that whatsoever the Church forgives—or doesn’t forgive—will apply to us even in heaven.
The importance of this teaching, especially as it pertains to the forgiveness of sins, goes beyond its Scriptural implications. Protestants have argued for centuries against the saving power of the Sacraments. Luther himself, in the first three paragraphs of his 95 theses, maintains:
"(1)When our Lord and Master Jesus Christ said, “Repent” [MATT. 4:17], he willed the entire life of believers to be one of repentance. (2) This word cannot be understood as referring to the sacrament of penance, that is, confession and satisfaction, as administered by the clergy. (3) Yet it does not mean solely inner repentance; such inner repentance is worthless unless it produces various outward mortifications of the flesh."
Luther thusly started what would become a foundational argument of Protestantism against the divine authority of the Catholic Church. But the legitimacy and necessity of the Catholic Church is unencumbered by this singular and shallow argument. Protestant arguments against the Church are, in a general sense, largely misinformed; that is, oftentimes, as in the case of Martin Luther, the context of the original biblical message is not considered. Surface-level interpretations of Scripture can make for a poor, shallow argument. Indeed, when Christ bequeathed the keys to Peter, it was clearly understood to be a bestowal of power and authority. Understanding what Christ was actually saying, as Steve Ray, a well-known Catholic apologist and convert to the faith, explains, “[t]he early Jewish converts would not have been confused or uncertain about what Jesus meant by these words.”
In acknowledging that the Catholic Church possesses the sole and complete authority on earth to forgive, or loose, sins, the impediment of understanding to how it works begins to dissolve. Along with all of the other Sacraments instituted by Christ, the Sacrament of Reconciliation acts as a means of reconciling us to the God who loves us. Further, it is not the will of God that his children are lost, but rather, Christ died that we might be found, and preserved, for the glory of his kingdom. In that way, and for that purpose, the Catholic Church is “endowed with heavenly riches,” which, guided by the Holy Spirit and sustained by Christ, allow her to continue on her holy mission to proclaim the gospel, forgive sins, and lead all souls to Christ who saves us. Indeed, in the words of St. Augustine, “Were there no forgiveness of sins in the Church, there would be no hope of life to come or eternal liberation. Let us thank God who has given his Church such a gift.”
 St. Augustine, as quoted in: CCC 981
 See Matthew 16:19
 Armbrust, Kevin, “The 95 Theses: A Reader’s Guide,” lcms.org, https://blogs.lcms.org/2017/luthers-95-theses-a-readers-guide (accessed November 3, 2017).
 Ray, S. K. (1999). Upon This Rock: St. Peter and the Primacy of Rome in Scripture and the Early Church (p. 270). San Francisco: Ignatius Press, 270.
 Conf. CCC 605
 CCC 771; see also, Lumen Gentium, 8.
 St. Augustine, as quoted in: CCC 983.