Why the Church had to say who Jesus is

🎯 Objectives

By the end of this lesson you will be able to:

explain what Christology is and why it concerns the life of every believer;
recognize the main ancient errors about the person of Christ;
understand how the Church responded by going back to the Scriptures, and why the same questions return today.

📖 Receive

Read Matthew 16:13-17 slowly, then 1 John 4:1-3.

“And Simon Peter answered and said, Thou art the Christ, the Son of the living God.” — Matthew 16:16 (KJV)

Notice two things. Jesus does not ask his disciples what they think of his teaching, but who he is. And John, a few decades later, warns that not every teaching about Jesus comes from God: it must be examined.

🔍 Examine

The most important question

At Caesarea Philippi Jesus asks two questions. The first is easy: “Whom do men say that I the Son of man am?” The answers are many: John the Baptist, Elijah, Jeremiah, one of the prophets. The second is personal: “But whom say ye that I am?”

Two thousand years later, people’s answers are still many: a moral teacher, a revolutionary, a mystic, a myth. But the question addressed to the disciples remains the same, and the answer is not a matter of indifference. If Jesus is only a man, the cross is the death of a righteous man but it cannot save us. If he is God but not truly man, he has not really taken our place. Who Jesus is decides what the cross, salvation and faith mean.

What Christology is

The word comes from the Greek Christós (Christ, the Anointed One) and lógos (word, discourse). Christology is the orderly study of what the Bible teaches about the person of Christ (who he is) and about his work (what he has done).

It is not an exercise for specialists. Jesus is the center of Scripture: he himself said of the Scriptures, “they are they which testify of me” (John 5:39). Studying Christ means reading the whole Bible with the right key, and above all knowing better the One we love and worship.

The errors that denied his deity

Already in the first centuries some groups reduced Jesus to a mere man.

Ebionism, widespread in Jewish-Christian circles, saw Jesus as an exceptional prophet, the natural son of Joseph and Mary, chosen by God for his faithfulness to the Law. A great man, but only a man.
Arianism was far more insidious. In the fourth century the presbyter Arius of Alexandria taught that the Son is the first and highest of creatures: existing before the world, but not eternal like the Father. His motto was: “there was a time when the Son was not”. The Council of Nicaea (325) answered by confessing the Son “of the same substance” (in Greek homooúsios) as the Father.

The errors that denied his humanity

Others made the opposite mistake: a Christ so divine that he was not really human.

Docetism (from the Greek dokéō, “to seem”) taught that Jesus’ body was only an appearance. Behind it lay the Greek idea that matter is evil and unworthy of God.
Cerinthianism, linked to Cerinthus, distinguished the man Jesus from “the Christ”, a heavenly power that came down on him at his baptism and withdrew before the cross.

John seems to be answering ideas of exactly this kind: “Every spirit that confesseth that Jesus Christ is come in the flesh is of God” (1 John 4:2; see also 2 John 7).

The errors about the Trinity and the union of the natures

Monarchianism wanted to defend the oneness of God, but sacrificed the distinction of the persons. In its “modalist” form (associated with Sabellius) Father, Son and Spirit were only three masks of the one God: so on the cross the Father himself would have died.
Apollinarianism (from Apollinaris of Laodicea, fourth century) taught that in Jesus the human mind was replaced by the divine Logos. But a Christ without a human mind is not fully human, and what has not been assumed has not been redeemed.
Nestorianism, linked to Nestorius, patriarch of Constantinople, stressed the distinction of the two natures so much that it risked making Christ two persons side by side. The Council of Ephesus (431) reaffirmed that there is only one Christ.
Eutychianism, at the opposite extreme, merged the two natures into one. The Council of Chalcedon (451) confessed one Christ “in two natures”, united without confusion and without separation. We will return to this in lesson 8.

📌 Two ravines and a path

Almost all errors about Christ fall into one of two ravines: taking something away from his deity or taking something away from his humanity. The path of Scripture runs between them: Jesus is true God and true man, one single person.

How the Church responded

The councils did not invent a new faith. Pastors and theologians went back to the Scriptures, compared them and looked for precise words to say what the Bible teaches, ruling out what contradicts it. The creeds are like a fence: they are not the pasture, but they protect the flock.

The timeline below summarizes the four great ancient councils and the error each one answered. Look at it carefully: each step arises from a concrete question put to the Church, not from a desire to complicate the faith.

timeline
    title The great councils and the errors about Christ
    325 : Nicaea : against Arius, the Son is true God
    381 : Constantinople : against Apollinaris, the Son is true man
    431 : Ephesus : against Nestorius, one single person
    451 : Chalcedon : against Eutyches, two natures without confusion

The table helps you see at a glance where each error falls in relation to the “two ravines”:

Error	What it takes away	Biblical answer
Ebionism, Arianism	full deity	John 1:1; Colossians 2:9
Docetism, Apollinarianism	full humanity	1 John 4:2; Hebrews 2:17
Nestorianism	the unity of the person	John 1:14
Eutychianism	the distinction of the natures	Philippians 2:6-7

Why these debates were not “just words”

Sometimes people say that the councils quarreled over nuances, such as the famous difference of a single letter between homooúsios (“of the same substance”) and homoioúsios (“of similar substance”). In reality, behind those words lay the decisive question: who saves us?

Athanasius of Alexandria, the great defender of Nicaea, reasoned like this: if the Son is a creature, however exalted, then a creature has saved us, and we worship a creature. But Scripture says that only God saves (Isaiah 43:11) and that only God is to be worshiped. In the same way, the defenders of Christ’s humanity said: if the Son did not assume a true human nature, complete with body and mind, then he has not really taken our place. Gregory of Nazianzus summed it up in a phrase that became famous: what has not been assumed has not been healed.

Every error about Christ, sooner or later, becomes an error about the gospel.

The same questions today

These errors are not museum pieces. Today there are those who present Jesus as a great teacher but not as God; those who consider him a created heavenly being; those who turn him into a spiritual idea without history. Paul was already warning the Corinthians not to accept “another Jesus” (2 Corinthians 11:4). Knowing the ancient errors helps us recognize them when they return under new names.

A practical example

Imagine reading this sentence on social media: “Jesus was the greatest enlightened one in history: he discovered the divine spark that is in each of us”. It sounds respectful, but try examining it with three questions. What does it say about his deity? Jesus becomes a man who “discovered” something, not the eternal Son. What does it say about his work? There is no cross and no forgiveness: an inner knowledge would save us. What do the Scriptures say? John 1:1-14 presents the Word who was God and who became flesh; Romans 3:23-25 speaks of sin and redemption. In a few lines you have recognized a modern echo of ancient Gnosticism. This is exactly the fruit of Christology: discerning calmly, without fear and without aggression.

🔗 Connect

Jesus’ question runs through the whole of Scripture:

John 20:31: the gospel is written so that we may believe that Jesus is the Christ, the Son of God, and have life in his name. The truth about Christ is bound up with life.
Colossians 2:8-9: Paul warns against empty philosophies, because in Christ dwells all the fullness of the Godhead bodily.
Jude 3: we are called to contend earnestly for the faith once for all delivered.
Acts 17:11: like the Bereans, we examine every teaching about Jesus in the light of the Scriptures.

🙏 Apply

If a friend asked you today “who is Jesus to you?”, what would you answer in three sentences?
Which of the two “ravines” seems more common in the culture you live in: a Jesus who is only a man, or a distant Jesus who is hardly human?
Have you ever heard teachings about Jesus that left you uneasy? How could you examine them with the Bible?
Thank God for the faithfulness of those who, before us, guarded the truth about Christ.

📚 Go Deeper

Read 1 John 4:1-6 and 2 John 7-11: how did the first Christians apply the criterion of Christ’s “flesh”?
Read the Niceno-Constantinopolitan Creed (381) and underline the phrases that speak of the Son: which error does each one rule out?
If you have taken the course Who Is Jesus, review the lesson “Recognizing the true Jesus”: here we will go deeper.

In the next lesson we will enter the heart of Jesus’ identity: what does it mean that he is the only begotten Son of the Father?