Without the resurrection Christianity is not a sustainable truth. Absent the resurrection, we would remain in darkness, without the hope of redemption. Lost for all eternity. The resurrection of Jesus is the foundation of our faith. Without it God's grace is of no consequence. When Jesus rose from the dead, he authenticated his identity as the Son of God, the work of atonement, redemption, reconciliation, and salvation was fulfilled. It was the physical raising of Jesus from the dead.
