Irenaeus of Lyon (c. 130–202 AD) was an early Church Father and apologist. His major work “Against Heresies” defended orthodox Christianity against Gnosticism and articulated the concept of recapitulation—that Christ recapitulates all stages of human life to restore humanity to God.
Born in Smyrna (modern Izmir, Turkey), Irenaeus was taught by Polycarp, who had known the Apostle John. He later became bishop of Lyon in Gaul (France), where he worked to spread Christianity among the Celtic peoples.
Irenaeus famously wrote that “the Word of God became what we are, that He might bring us to be even what He Himself is.” This became a foundational statement of theosis in Christian theology. His vision of human destiny as participation in divine life has profound resonances with Latter-day Saint teachings on eternal progression and becoming like God.