Sources of Authority on Incarnation

Why Jesus is an authority for Christian life

For Catholics, the incarnation means that God the Son became human in Jesus, who is fully God and fully human. This explains why Jesus is more than a wise moral teacher: his teaching reveals God’s will, while his human life shows how that will can be lived.

Catholics encounter this teaching through three connected sources of authority. Scripture records Jesus’s life and words. Tradition hands on the Church’s understanding of them, including the writings of early teachers such as Irenaeus. The Magisterium, the teaching authority of the Pope and bishops, explains Catholic beliefs through documents such as Dei Verbum and Verbum Domini.

Fulfilling the law rather than replacing it

The Old Testament law includes the commandments given by God to Moses. Jesus places his teaching within this Jewish tradition, saying: “I have come not to abolish but to fulfil” the law and the prophets (Matthew 5:17).

To fulfil the law means to bring it to its intended purpose, not to make it irrelevant. Jesus perfectly lives according to God’s will and teaches people to look beyond outward obedience to their motives and attitudes. Avoiding a forbidden action is not the whole of moral goodness: a person should also develop a loving character.

A virtue is a good moral quality which shapes someone’s choices. Catholics regard Jesus as a model of virtues because his perfect humanity shows what a life fully directed towards God looks like. His teaching encourages mercy, humility, purity of heart and peacemaking; his obedience to the Father shows these qualities belong to a way of life, not just a list of ideas.

The Beatitudes: the attitudes of God’s kingdom

The Beatitudes open the Sermon on the Mount in Matthew 5:1–12. The word comes from a Latin word meaning blessed or happy. Here, being blessed means receiving God’s favour: Jesus is not promising that his followers will always have comfortable lives.

Each Beatitude connects an attitude or circumstance with a promise:

Jesus also reassures those insulted or falsely accused because of their commitment to him that their reward in heaven is great.

These teachings challenge the idea that happiness depends on wealth, power or popularity. They also deepen moral obedience: someone might avoid violence yet do nothing to make peace. The Beatitudes encourage the positive virtue of peacemaking. Similarly, mercy requires more than avoiding cruelty; it involves actively responding with compassion.

Helping people in need: the Sheep and Goats

In Matthew 25:31–46, Jesus describes judgement using the image of a shepherd separating sheep from goats. The decisive distinction is how people have responded to those in need.

The actions Jesus names are concrete:

• Feeding the hungry.
• Giving drink to the thirsty.
• Welcoming strangers.
• Clothing those who lack clothes.
• Caring for the sick.
• Visiting prisoners.

Jesus identifies himself with those who receive this care: “I was hungry and you gave me food” (Matthew 25:35). Those who helped did not realise that, through their service to others, they were serving him. Those who failed to help likewise failed to serve him.

The teaching therefore connects love of God with practical love of other people. It presents care for those in need as a serious moral responsibility, linked to judgement and eternal life, rather than an optional extra. For example, supplying food to someone who is hungry puts this teaching into action; merely feeling sympathy does not meet the person’s need.

Together, the two passages connect character and action. The Beatitudes encourage merciful attitudes; the Sheep and Goats shows what mercy looks like in practice.

Irenaeus: a human being fully alive

Irenaeus of Lyon, an early Christian teacher who lived around AD 130–202, explored how Jesus reveals God to humanity. His work Adversus Haereses means Against Heresies: it defended Christian belief against teachings the Church considered false.

In Adversus Haereses 4,20,7, the phrase studied is: “The glory of God is a human being, fully alive.” It is connected with the further statement that human life is the vision of God. Together, these ideas link true human life with knowing God.

“Fully alive” does not simply mean being physically healthy, wealthy or successful. It means living in openness to God and fulfilling the purpose of human life. Jesus displays this perfectly: as the incarnate Son, he reveals God’s qualities through a fully human life entirely directed towards the Father.

The phrase also has significance for other human beings. By following Jesus’s teaching and example, people can become more fully alive and reflect God’s glory through their own actions. Showing mercy or helping someone in need is therefore not merely obeying a rule; it is part of becoming the person God intends them to be.

Irenaeus’s teaching connects belief in the incarnation with moral life. God is beyond complete human understanding, but Jesus makes God known. Human life can reveal God’s goodness rather than being something separate from, or opposed to, closeness to God.

Dei Verbum 4: Jesus reveals God and brings salvation

Dei Verbum, meaning “God’s word”, was issued by the Second Vatican Council in 1965. Paragraph 4 explains that God sent his Son to dwell among human beings and reveal God’s innermost being.

It describes Jesus as the “Word made flesh”, sent as “a man to men”. This brings together his divinity and humanity: the one who reveals God is genuinely human, not merely appearing human.

The paragraph also calls Jesus “God with us”. The incarnation has a saving purpose: Jesus comes to free humanity from sin and death and bring eternal life. Its emphasis is therefore on Jesus as God’s revelation and the one who brings salvation.

Verbum Domini 12: the divine Word becomes accessible

Verbum Domini, meaning “the word of the Lord”, was written by Pope Benedict XVI in 2010. Paragraph 12 describes the Son as the Logos, the eternal divine Word.

It uses the striking image of the eternal Word becoming “small enough to fit in the manger”. Becoming a child makes God accessible to human understanding. This does not mean that Jesus stops being divine: the eternal Word is present in a genuinely human life.

The paragraph also emphasises that Jesus, in his perfect humanity, always does the Father’s will. It calls him the “new Adam” and “true man”. These descriptions present Jesus as the model of humanity obedient to God, including when obedience leads to his death.

Comparing the two documents

Both documents teach that Jesus is the divine Word who truly becomes human and makes God known. Neither presents him as half-God and half-human, only a holy man, or God merely disguised as a person.

Their emphases differ. Dei Verbum 4 concentrates on the Son revealing God and freeing humanity from sin and death. Verbum Domini 12 highlights how the eternal Word becomes accessible as a child and how Jesus’s perfect humanity fulfils the Father’s will.

These are complementary explanations. One particularly stresses what Jesus reveals and accomplishes for humanity; the other particularly stresses how God becomes approachable and what true human obedience looks like. Both help explain why Catholics regard Jesus as their authoritative teacher and model of moral life.