The inquiry begins with a question attributed to Jesus himself: who is he to his disciples? Frédéric Lenoir does not claim that historical research can penetrate Jesus’s inaccessible inner identity. Instead, he follows the formation of successive answers, from first-century testimony to conciliar definitions. The problem originates in a tension within the earliest Christian sources. Jesus appears fully human, yet related to God in an exceptional way; his disciples also claim to have seen him risen from the dead. The book therefore distinguishes the Jewish man from Galilee, his first followers’ interpretations, and the theological constructions developed later.

The sources neither date from the same moment nor speak with one voice. Paul’s letters stand relatively close to the movement’s beginnings, while Mark, Matthew, and Luke arrange traditions about Jesus in different ways. The later Gospel of John belongs to another stage of reflection. Lenoir stresses discrepancies, confessional purposes, and uncertainties of authorship. These documents do not provide a neutral biography. They nevertheless disclose a Jewish Jesus who was circumcised, strictly monotheistic, and immersed in the arguments of his people. He did not consciously establish a separate religion called Christianity.

This Jesus resists classification. He shares certain convictions with the Pharisees but condemns the distance between their learning and their conduct. His criticism of the Temple resembles that of the Essenes, yet he rejects their separation from people deemed impure. His freedom regarding the Sabbath and ritual observance is not mere rebelliousness. It subordinates rules to inward improvement, care for the weak, and even love of enemies. The traditions also portray him as a wisdom teacher, prophet, healer, and worker of wonders. Each category explains something, but none fully accounts for the peculiar authority assigned to his words and actions.

After the crucifixion, proclamation of the resurrection changes how the master is understood. His followers reread his life through Jewish scripture and accumulate titles: prophet, Messiah or Christ, Son of Man, Son of God, and Lord. Every title can bear several meanings, and none displaces all the others. In the reported sayings, Jesus himself remains elusive about his identity and does not make himself the Father’s equal. Yet the missionary movement, especially through Paul, extends salvation to non-Jews and loosens its connection to circumcision and dietary law. Jerusalem’s destruction in 70 then deepens the separation. By the end of the first century, Christology remains plural. It asserts an extraordinary greatness but does not yet possess the language that will define Jesus as God incarnate.

The second part moves into the second and third centuries as the movement spreads through the Roman Empire. Communities establish themselves from city to city and, to some extent, in the countryside, while facing ridicule, suspicion, and intermittent persecution. Refusal to join civic cults makes Christians appear atheistic or hostile to public order. Their endurance, moral discipline, assistance to vulnerable people, and communal organization nevertheless support their growth. Bishops, priests, and deacons gradually provide structure, while baptism marks entry into the Church. This institutional consolidation gives the emerging “Great Church” the means to promote its teaching among many competing Christian groups.

The Gospel of John provides the decisive intellectual turn. Jesus is no longer only God’s envoy, Messiah, or favoured Son. He is the pre-existent Logos, the Word present before creation and made flesh in history. His existence comes from God and returns to God; Thomas can therefore acknowledge him as Lord and God. The fourth Gospel also assigns the Spirit a continuing role as advocate and guide after Jesus’s departure. This Christology makes a relation among Father, Son, and Spirit conceivable, but sharpens the central difficulty: how can Christians confess Christ’s divinity without abandoning the oneness of God, and how can they preserve his genuine humanity?

Answers proliferate. Docetism reduces Jesus’s humanity and suffering to appearance. Adoptionism treats him as a man chosen or adopted by God. Monarchianism and modalism draw Father and Son so close that they risk collapsing the distinction between them; subordinationism places the Son beneath the Father in being. Jewish Christians continue to observe Torah while disagreeing about Jesus’s birth and nature. At the opposite extreme, Marcion removes Christianity’s Jewish origins, opposes an Old and a New Testament, and edits his selected writings accordingly. Gnostic movements often separate the historical Jesus from a metaphysical Christ who gives saving knowledge to a small circle of initiates. Their internal variety precludes treating them as a single system, particularly on the status of women.

Orthodoxy, then, does not appear fully formed. The Great Church constructs it by opposing rivals, refining a rule of faith, and selecting recognized scriptures. The response to Marcion accelerates formation of a New Testament. Irenaeus defends four Gospels, while other works remain disputed and excluded writings become apocrypha. “Heresy,” originally a word for choice, gradually becomes a term of condemnation. On the eve of the fourth century, persecutions under Decius, Valerian, and Diocletian severely test the communities without eradicating them. They leave behind a more organized Church, a largely stabilized canon, and a theology still under dispute. Once imperial power changes sides, controversies about faith also become matters of state.

Constantine ends the persecutions and favours Christians, but expects their religion to serve imperial unity. The controversy surrounding Arius threatens that project. Arius argues that the Son, begotten by the Father, has a beginning. He is higher than other creatures but neither eternal nor of the same substance as God. Bishop Alexander and his allies reject this “second god.” Constantine initially treats the quarrel as a minor matter, then convenes Nicaea in 325 to prevent schism. Its creed declares the Son begotten rather than created and “consubstantial” with the Father. The contested Greek term homoousios, absent from scripture, becomes the definition’s safeguard. Constantine compels signatures, exiles Arius, and orders his books destroyed.

Nicaea does not produce the promised peace. Arius is recalled, his protectors recover influence, and several variants emerge, some describing the Son’s substance as merely similar to the Father’s. Arian Christianity spreads beyond the empire among the Goths through Wulfila. Emperors, synods, and bishops alternate condemnations, exiles, restorations, and compromise formulas. Apollinarius, an opponent of Arius, proposes a fully divine Christ in whom the Word replaces a human soul, thereby weakening the doctrine’s other pole, Jesus’s real humanity. Under Theodosius, the Council of Constantinople in 381 confirms the Nicene direction and states the Spirit’s divinity more fully. Orthodoxy becomes the state religion, enforced against dissenters by law.

The argument then shifts to the manner in which divinity and humanity are united. Nestorius, associated with the Antiochene school, distrusts the title “Mother of God” for Mary because he fears attributing fleshly birth, suffering, and death to the eternal Word. Cyril of Alexandria instead insists on the unity of Christ’s person: the one born and made to suffer is the whole Christ. Their conflict also involves rivalry among episcopal sees. At Ephesus in 431, Cyril opens proceedings before the eastern delegation arrives and secures Nestorius’s deposition; eastern bishops meet separately and condemn Cyril. The Formula of Reunion in 433 restores partial agreement around one Christ from two natures, but does not erase the lasting divisions.

Eutyches then radicalizes the Alexandrian position by virtually absorbing Christ’s humanity into a single incarnate nature. The council held at Ephesus in 449 restores him amid violence. Bishop Flavian is deposed, beaten, and dies on his journey into exile. Chalcedon, convened in 451 by Marcian and Pulcheria, reverses that decision, condemns Eutyches and Dioscorus, and defines one Christ in two natures, without confusion or separation. The formula does not end the story. It humiliates Alexandria, provokes revolts, and strengthens rejection among the churches later called the Churches of the Three Councils, including the Coptic, Syriac, and Armenian churches. The majority doctrine thus emerges from genuine conceptual work, but also from contested procedure, ecclesiastical rivalry, and imperial force.

By the end of the account, Christ’s divinity and Trinitarian doctrine have become common foundations of the major Christian confessions, surviving both the separation of Eastern and Western churches and the Reformation. Later disputes concern authority, discipline, morality, and ecclesiastical organization more than Christ’s nature. This stability has a historical cost. Rival doctrines are prohibited, their books destroyed, and their defenders exiled or silenced. Imperial law reserves public expression for Nicene Christianity. Lenoir does not therefore dismiss doctrine as a political contrivance. The controversies address genuine intellectual problems. His point is that theological investigation, institutional interest, and coercion remain intertwined throughout their resolution.

The epilogue returns to testimony that predates the councils. If an exact formula of three persons and two natures were required for authentic faith, the apostles’ faith would have to be judged defective, since they did not yet possess those concepts. Lenoir rejects that conclusion. He reduces the common ground of the earliest witnesses to two propositions: Jesus is a man with a unique relationship to God and a saving role as mediator; he died, was raised, and remains invisibly present. On this reading, the resurrection accounts do not describe the resuscitation of a corpse. They depict a transformation that combines personal continuity with a new mode of existence.

Lenoir then offers his own interpretation, which must be distinguished from the preceding historical reconstruction. God remains one and inaccessible in essence but is manifested in three dimensions: creatively in the Father, intelligibly in the Logos, and consolingly in the Spirit. Jesus incarnates the Logos because his life and words make God perceptible in human form, without exhausting the divine essence. This understanding leads Lenoir to characterize Christianity as a religion of person and presence. He contrasts Jesus’s concrete attention to individuals with the impersonal enforcement of religious law, using the woman accused of adultery and a modern excommunication imposed without adequate regard for a tragic situation as his examples.

The claim to retain is therefore neither that Jesus abruptly “became” God by a council’s vote nor that doctrine merely transmitted a formula complete from the beginning. The book describes a long transformation of language: Jewish titles reread after the resurrection, mission among non-Jews, John’s theology of the Logos, second- and third-century controversies, and definitions imposed and revised through councils. Its limits are those of its evidence, which is often late, confessional, fragmentary, or preserved by opponents. Such sources cannot reveal Jesus’s inner consciousness and require caution in reconstruction. History can establish stages, conflicts, and relations of power. It can neither validate nor disprove the resurrection, incarnation, or truth of faith. It can show that now-familiar formulas were achieved only after centuries of uncertainty.