In the eleventh chapter of his third book Irenaeus answers the Gnostic teachers of his day who wanted to use one Gospel only, or to invent new ones to suit their systems. The Church, he says, has received four Gospels and no more, and there could be neither more nor fewer than four.

Irenaeus reads the fourfold form as written into the structure of the world: the four corners of the earth, the four winds, the four covenants God has made with humanity (with Adam, with Noah, with Moses, with Christ), the four living creatures around the throne of God in the prophet Ezekiel and again in the Revelation given to John. The Gospel is one, but the witnesses to it are four, and the Spirit who breathes through them is one Spirit.

John, he says, is the lion in this scheme: the evangelist of Christ's eternal divine origin, the Gospel that opens above the world rather than within it. Later Fathers would shift the assignments, Augustine and others gave the eagle to John, but the underlying conviction is Irenaeus': the fourfoldness of the Gospels is not an accident of history but the form the Spirit gave to the apostolic witness.

In the fifth book Irenaeus returns again and again to the verse that runs through every page he writes: 'the Word became flesh'. His teaching of recapitulation is built on it. Christ, by becoming what we are, gathers up the whole of human nature into Himself. He passes through every age of human life, infancy, childhood, youth, adulthood, sanctifying each.

Adam fell, and in him the whole human race; the Word, becoming Adam's descendant, restores in His own person what was lost. Where the first Adam disobeyed at a tree, the new Adam obeys to the tree of the Cross. Where the first Eve heeded the serpent, the new Eve, the Theotokos, heeds the angel. Where the first man brought death, the second brings life.

Irenaeus' phrase, which the Eastern Fathers will echo for centuries, is plain: He became what we are that He might make us what He is. The Fourth Gospel's 'and the Word was made flesh' is not the start of Christ's humiliation only; it is the beginning of our exaltation.