No book in the Bible says more about the Trinity than the Gospel of John. Of the innumerable commentaries published on this much loved gospel, few have focused on this central theme. The author tries to listen to the discourses of Jesus in John and draw forth the disclosures of God's social nature in the activity of the incarnate Son. He discovers something quite remarkable about the attitude of the persons of the Triune Community, something he calls disposability. Father, Son, and Spirit are there for the other—servants who place themselves at the other person's disposal in an act of total generosity. They serve not only each other but also the fallen human race, and the creatures they redeem are invited to wash one another's feet as servants to the world. Devoted Bible students will find in this thematic commentary a dimension to the Gospel of John they may have noticed only vaguely. As they follow the author through this gospel chapter by chapter, they will acquire a far deeper understanding of the triune God, whom they serve because he has served them.