I am praying not only for these disciples but also for all who will ever believe in me through their message. I pray that they will all be one, just as you and I are one–as you are in me, Father, and I am in you. And may they be in us so that the world will believe you sent me (John 17:20-21, NLT). For most Christians these words of Jesus seem like an unreachable ideal. Or they promise spiritual unity without a visible demonstration between real people. Some even read these words with a sense of fear seeing this text used for a compromise agenda. How should we understand this prayer offered for all who follow Jesus? What if Jesus really intended for the world to believe the gospel on the basis of looking at Christians who live deep unity in a shared relationship with him? What if there is way of understanding what Jesus desired so that we can begin anew to tear down the many walls of division that keep the world from seeing God’s love in us? Is our oneness much bigger and deeper than we could imagine? John Armstrong has devoted three decades to the work of Christian unity. His story and ministry have encouraged many around the world and now they are reflected in this memoir of a life devoted to unity.