Perhaps the only Catholics who correctly understand Sunday's three readings are those who recently have been baptized or accepted into the Church. "Born-Catholics," whose Jesus-experience is based on and accompanied by an experience of a tightly structured, hierarchical Church, probably will have a hard time appreciating the significance of these particular scriptural passages.
Those for whom our liturgical writings originally were composed started and maintained their faith through a direct relationship with Jesus. The first Christians didn't expect the Church to mediate that relationship. The Church's role simply was to introduce those who wished to grow into such a rapport to the experience of doing do. It both supported and fostered individuals in this endeavor, supplying the environment in which their relationship with Jesus was daily experienced and grew.
No one in the early Church ever thought a link to an institution could replace a relationship with Jesus. A direct tie-in to Jesus was essential for faith and salvation.
As John quotes Jesus in the Gospel (Jn 10:1-10), "Amen, amen, I say to you, whoever does not enter a sheepfold through the gate but climbs over elsewhere is a thief and a robber....I am the gate. Whoever enters through me will be saved, and will come in and go out and find pasture."
John uses symbolic, shepherding images in this passage to describe an experience which all Jesus' disciples have. Eventually, everything revolves around Jesus. They experience Him in every dimension of their lives.
That's why first-century Christians didn't need Scripture scholars to help them understand the central statement in the second reading (I Peter 2:20-25): "Christ suffered for you...and left you an example, to have you follow in His footsteps. He did no wrong; no deceit was found in His mouth. When He was insulted, He returned no insult. When He was made to suffer, He did not counter with threats. Instead, He delivered Himself up to the One who judges justly....By His wounds, you have been healed. For you had gone astray like sheep, but you have now returned to the shepherd and guardian of your souls."
The writer didn't have to teach his reachers something they already knew. From the beginning of their faith journey, they were as close and dependent on Jesus as sheep are on shepherds.
Luke, in the first reading (Acts 2:14, 36-41), is interested in conveying just one important question: "What are we to do, brothers?" It's a question only asked by those for whom the door of faith is opened. But it's significant that we notice the crowd asks it of individuals who have already experienced the risen Jesus in their lives, those who know what it means to depend totally on Jesus.
So we should logically expect Peter's response to contain the basics of Christianity: "You must reform and be baptized, each one of you, in the name of Jesus Christ, that your sins may be forgiven; then you will receive the gift of the Holy Spirit."
In Semitic thought, when someone does anything in another's "name," he or she does it as the named person would do it. For all practical purposes, the two become one, as happens with the Christian and Christ.
The reform which precedes Baptism is nothing more than followers of Jesus making His value system their own. And it's because they've become new people that their sins are forgiven. They're not the people who've committed them. Those sinful individuals have died; they're now one with the risen Jesus who shares His Spirit with them so that they'll always know "what to do" in the future.
Thankfully, the restored catechumenate has introduced those seeking the faith to the process which the earliest disciples of Jesus thought essential for conversion. They seem to be thriving on it. There's only one problem: If we "born-Catholics" don't return to the same process, our newly baptized won't have a real Christian community within which to grow in their direct, unique relationship with Jesus.