The authority we acknowledge in or attribute to a person or an institution is normally associated with identity: who or what they are defines their authority. Indeed, whom or what we acknowledge someone or something to be is usually the central question.

Jesus today asks His Apostles the “who” question. It’s hard understanding how a text fits into the overall Gospel when we read individual excerpts every week. But the Gospel was written as a whole. You might not think that the turning point of Mark’s Gospel, which we have been reading every Sunday since last Advent, would appear on Sept. 16.

But it does. Today’s Gospel is, actually, the turning point of Mark’s Gospel. It’s right in the middle. Things have been leading up to it and, now that Peter has confessed the faith of the Apostles that Jesus is “the Christ,” everything will follow from that acknowledgement.

The core question is: who is Jesus? Jesus has been doing all sorts of things, especially healings, which indicate who He is. Now, as He and the Apostles reach Caesarea Philippi, Jesus poses two questions.

On the surface, they seem similar. But they could not be more different.

The first question—“Who do people say that I am?”—is a reporter’s question. “Okay, men, we’ve been traveling around Israel for a while. What’s the word on the street? Who are people saying about me?”

One can answer that question neutrally, without any personal involvement. “Well, X said this, Y thought that, and Z has no opinion.” “John the Baptist, others Elijah, still others one of the prophets.”

The second question—“But who do you say that I am?”—is not just factual. It’s up close and personal. It can’t be answered in an objective manner that leaves the respondent disengaged. It’s an existential question. How I answer it (a) defines our relationship going forward and (b) commits me to something.

“You are the Christ,” says Peter on behalf of the Twelve. “You are the Anointed One. You are the One God sent.”

Just three weeks ago, Jesus posed a similar question in the Gospel of John. When the crowd that was initially enthusiastic about the man who provides bread chooses to wander off after Jesus’ Eucharistic teaching, Jesus asks the Twelve if they want to leave, too. “Where shall we go?” asks Peter. “You have the word of everlasting life.”

Jesus exacts a commitment from His followers, even though their understanding of “the Christ” is still inchoate. This week, Peter answers well. Jesus then starts talking that “the Son of Man must suffer greatly.” Although it’s omitted from this week’s reading, within four verses Peter doesn’t do so well in the answers department. When Peter rebukes Jesus for being a downer and pushing this suffering stuff, Jesus even calls him a “Satan.” The Apostles have some idea of whom Jesus is, but it is incomplete and it is loaded down with lots of other mental baggage (like the Anointed One who will come in glory to liberate Israel politically). That is why Jesus repeatedly tells the disciples not to talk about what they see and experience “until the Son of Man is raised from the dead.” Because until Jesus has suffered, died, and risen, the Apostles cannot understand who He is. But in the light of the Passion, Death, and Resurrection, they can take “the Christ” as coequal, “consubstantial” with God—as God Himself.

It takes a while to see the whole truth. When you’re in a dark room, turning on a 250-watt bulb doesn’t help you see better. It blinds you. It takes time to adjust to the whole truth.

Because the Apostles eventually understand “who I AM,” they attribute to Him the “words of everlasting life.” What Jesus teaches, what He prescribes, what He forbids, gets its authority from who He is. Whom you confess Him to be is critical to the authority you accept from Him.

Thomas Jefferson answered “who do you say I am” as Jewish Confucius or Plato –Jesus is a wise ethical teacher who taught some inspiring things about which the “Sage of Monticello” would decide was or was not worth following. But he certainly said He was not a god. Jefferson’s God was essentially a divine clockmaker who wound up the universe and remained aloof from it. Yes, he threw a reference to “reliance on Divine Providence” into the Declaration of Independence,” but it’s hard to see how Providence played much of a role for a Deist “god.”

So, Jesus’ core question is the turning point: it follows, depending on “who do you say I am,” whether Jesus is just a moral sage, maybe even a prophet, whose teaching is as good as the reasons I discover behind it, or if He is the “Christ, the Son of God” whose divinely originated teaching by the very nature of that teaching demands my assent.

So what does this have to do with Humanae vitae?

Humanae vitae is not just a question of moral teaching. It also involves an understanding of “what do you say the Church is?” The identity you acknowledge in the Church is intrinsically connected to the authority of its teaching.

Catholics understand the Church is the continuation of Christ’s Body in space and time. Jesus did not just simply teach and leave. “I am with you all the days, until the end of the world.”

In other Gospels, Peter’s confession of Jesus’ identity is tied up with Jesus’ conferring upon Peter the “power of the keys,” i.e., the power to absolve or retain sins. But to forgive or retain sins presupposes knowing what is right and wrong, i.e., being able to teach what God permits and what He prohibits. Because Jesus promises “I will not leave you orphans,” bereft of moral teaching to lead you through life.

Yes, the Church has a human side and – as we can see from the recent clergy sex scandals—that side can be ugly. I recently read a commentator who, living through the sordid filth of the last month, said he finally understood how the Reformation happened. Conservative commentator J.J. McCullough observed how what should be heavenly has been thrust into the gutter: “A Church whose most powerful appeal rests on transcendent claims now looks very much of this world.”

And yet Peter denied Christ and, according to legend, was ready to do it again as he fled Nero’s Rome. Most of the Apostles ran away. The Church has had great sinners even in leadership roles. It was Boccaccio, I think, who said that if this Church was only human, it would have been gone a long time ago.

But it isn’t.

And even though people have been ready to write its epitaph, just as they were ready to declare “God is dead,” both are still alive.

And that means that the Church has to teach. Because that is what her mission is. Even on matters of sexual ethics. Even when she shoots herself in the foot by compromising her teaching witness with practical infidelity.

So, we have to get back to the question: “what do you say the Church is?”

If we admit that, in terms of teaching people what God wants of people in their lives (prescinding from the dissonance between preaching and practicing), that is what the Church is here for, then we have to ask: “what do you say the Church is?” Is it just a human institution, in which case we are all Lone Rangers, orphans hoping somehow to figure out how God wants us to live in a complex world very different from Jesus’, aiming somehow to “get it right” and “get to heaven?” If that’s the case, then the Church’s teaching is only as good as I discover it to be.

But that is not what Catholics understand the Church to be. Nor does Scripture tell us we are orphans, left to our own devices to figure out right and wrong. Whatever moral warts its clergy may have, the Church’s moral teaching claims to embody God’s: what you bind on earth is bound in heaven, what you loose on earth is loosed in heaven.

Yes, I understand the complexity of moral teaching, the historical development of the Church’s moral teaching, etc. Acknowledging all of that, I still insist—as does the Church—that her moral teaching is more than just the Pope’s prudential advice, as good as the particular Catholic thinks it is. That’s why this teaching is a matter of moral assent, not just individual take-it-or-leave-it.

In the debate over Humanae vitae, part of the discussion centered on the moral teaching (what the Church was saying about sexual morality) but part of it centered on ecclesiology (what the Church says it is). Sex is not marginal to most people’s lives. It is action that practically implicates most people. And, despite changing mores, there are certain constants to sex. It can give life. And it can join spouses together.

If the Church as the Body of Christ—as His continued Presence in a world in which He has not left us orphans—cannot teach with moral authority and clarity on a matter so fundamental to most people’s lives, or if that teaching is wrong, then the Church is not what it says it is.

The Church has consistently taught that the procreative and unitive meanings of the sexual act cannot be morally separated on human initiative. That teaching has been expressed in various ways and forms, and the formulation above is essentially how it appears in the encyclical. But its essence has been what the Church has taught as the bottom line of Catholic sexual ethics consistently. Indeed, all Christians held that position until 1931, when the Anglican Church first broke away from the unanimous Christian consensus. The Catholic Church still teaches that teaching today.

Consider what that means. The Church has been divided about many things. The Reformation split Christianity over what is the Eucharist—the “body and blood, soul and divinity” of Jesus Christ, Jesus-in-bread, a symbolic reminder of Jesus, or just something-He-said-to-do-so-we-do-it. If Christians were able to maintain a moral consensus about what was moral and immoral in matters sexual for 20 centuries—even when they divided over other things—doesn’t that suggest this is the Christian way?

So, either the Christian Church was really wrong about a really basic aspect of life for almost two millennia (with the Catholic Church stubbornly persisting in error until today) – in which case, please quit the Christian Church, which is a most incompetent moral teacher – or, despite the individual faults of individual clergy, the Church’s moral teaching has consistently embodied, for over 20 centuries, what God expects of His disciples in the area of sexual morality.

And so, we’re back to two questions: “What are people saying about the Church?” And the more important, the existential question for you: “what do you say the Church is?”