Irenaeus' presentation of Christ as the New Adam is based on Paul's Christ-Adam parallel in Romans 5:12–21. Irenaeus uses this parallel to demonstrate that Christ truly took human flesh. Irenaeus considered it important to emphasize this point because he understands the failure to recognize Christ's full humanity the bond linking the various strains of Gnosticism together, as seen in his statement that "according to the opinion of no one of the heretics was the Word of God made flesh." Irenaeus believes that unless the Word became flesh, humans were not fully redeemed. He explains that by becoming man, Christ restored humanity to being in the image and likeness of God, which they had lost in the Fall of man. Just as Adam was the original head of humanity through whom all sinned, Christ is the new head of humanity who fulfills Adam's role in the Economy of Salvation. Irenaeus calls this process of restoring humanity recapitulation.