When I was in high school I read a short explanation of the Catholic faith. The author laid down this challenge: if one believes Jesus is God one cannot avoid the Catholic Church as founded by Him. They go together like a spring and its stream.*
Eight years of seminary study and subsequent decades as a parish priest have increased my belief in the Catholic Church as Jesus' way of continuing his presence in time and space. I have staked my life on that faith. Anyone who has read the articles and homilies on this website know that I constantly return to this point: the teachings of the Church are the very teachings of Jesus himself.
Still it would be easy for someone to write me off, "Of course he believes that. He is a life-long Catholic. What's more, as a priest, he has a vested interest in saying the Church speaks for Jesus." It is not so simple to write off Mark P. Shea. He was Evangelical who to this day feels immense gratitude for the blessings he received through that faith. It was hard for him to leave his vibrant community, especially considering the present state of the Catholic Church.
In his short book By What Authority? Mark explains why he made such a drastic move. As the subtitle indicates it is the story of of how "an Evangelical discovers Catholic Tradition." Even life-long Catholics will be amazed at what he finds. We need to re-discover Tradition. Let's face it - many Catholics have imbibed the mistaken idea of Martin Luther: Sola Scriptura, the Bible interprets itself. Vatican II does not teach that. Rather the Council insists the Bible must be interpreted in terms of Tradition.**
Mark Shea illustrates this truth by showing how certain doctrines deeply cherished by Evangelicals (as well as by Catholics) cannot be established on the basis of Sola Scriptura. He gives three examples: the sanctity of human life (vs. abortion), the exclusivity of marriage (vs. polygamy) and the Trinity (vs. Arianism, the doctrine that Jesus is not God, but was created in time). He shows how the Bible can be used to defend abortion, polygamy and Arianism. There are of course abundant quotes against those heinous teachings, but the point is you could never resolve any of them just by exchanging Scripture texts. You need to look at how the Church has authoritatively interpreted the Bible from earliest times.
By What Autority? shows that the Bible by itself is not sufficient. We need an authority outside the Scriptures. Jesus gave us that when he set up the college of apostles and their successors, the pope and bishops. The most dramatic example of this necessity is the canon, that is, the very list of books which belong in the Bible.
Sola Scriptura appeals to the modern mind because we are accustomed to the printing press. We can easily have the morning newspaper delivered to our doorsteps. Many folks vaguely imagine that Jesus entrusted the Bible whole to the apostles before he ascended into heaven. Truth is he gave them no written document. He taught orally and the disciples handed on his teaching by the spoken word. It took several decades for the 27 books of the New Testament to be written - and much longer for them to be officially recognized as inspired. But who had the authority to "canonize" them? There was intense controversy over which books belonged, e.g. some considered the Letter to the Hebrews doubtful, while others wanted to include the Teachings of the Twelve Apostles.
Mark Shea takes up the various Evangelical attempts to keep the canon without appealing to the authority of the Catholic Church. None of them work and we are left with the question, "By What Authority?" If the Bible does not guarantee itself, who can guarantee it? To answer that we can learn from Joseph and Mary. They found Jesus teaching in the Temple - an image of the visible Church. (cf. Lk 2: 46f.) To those still at the doors, the invitation is clear, "The Spirit and the Bride say, 'Come.'" (Rev 22: 17)
We welcome Evangelicals like Mark Shea with immense gratitude to God. They bring a vivid sense of the uniqueness of the Church. They also underscore a virtue we forget: humility before an authority established by Jesus himself. As a help toward that humility I encourage you to read By What Authority?. While you are at it, please pick up the even more compact companion volume This is My Body. (An Evangelical Discovers the Real Presence.)
*The analogy limps in as much as a stream cannot return to its source, but it does give some image of identification and total dependence.
**"But in order to keep the Gospel forever whole and alive within the Church, the Apostles left bishops as their successors, "handing over" to them "the authority to teach in their own place" . This sacred tradition, therefore, and Sacred Scripture of both the Old and New Testaments are like a mirror in which the pilgrim Church on earth looks at God, from whom she has received everything, until she is brought finally to see Him as He is, face to face (see 1 John 3:2)." (DOGMATIC CONSTITUTION ON DIVINE REVELATION - Dei Verbum, 7)
Other articles on why this authority is necessary:
Flawed Expectations (the Reception of the Cathechism).
Dissent: An attempt to have your cake and eat it too?
Does Dogma Divide?
The crisis in Catholic Universities.
Other Recommended Books.