Introduction: John's Gospel and the church's Doctrine of the Trinity -- The approach of the present study -- Historical context -- John's Gospel and Jewish monotheism -- John's context -- John's portrayal of Jesus and Jewish monotheism -- The background of John's portrayal of Jesus' pre-existence -- Christ-devotion and exclusivist Jewish monotheism -- Implications for John's Gospel -- Biblical foundations -- God in John's Gospel -- The book of signs -- The book of glory -- The Father in John's Gospel -- The book of signs -- The book of glory -- The son in John's Gospel -- One-of-a-kind son -- Son of God -- Son of man -- The son -- The spirit in John's Gospel -- The book of signs -- The book of glory -- Father, Son and Spirit in John's Gospel -- Theological reflections -- Christology in John's trinitarian perspective : Jesus' filial identity -- The prologue : John's initial characterization of Jesus as the Son -- Jesus' filial identity and divine agency -- Jesus' filial identity and the nature of salvation -- The spirit who rests and remains on God's son and his brothers -- John's initial characterization of the spirit in relation to Jesus : book of signs -- Initial summary : Jesus and the spirit in the book of signs -- John's Fuller characterization of the spirit in relation to Jesus and the disciples : book of glory -- The spirit who rests and remains on God's son and his brothers -- Father, Son and Spirit -- 'As the Father has sent me, so I am sending you' : toward a trinitarian mission theology -- God (theos) -- The Father -- The Son -- The Spirit -- Father, Son and Spirit : the three persons of the Godhead united in one mission -- The Trinity and the church's mission -- The Trinity and John's Gospel -- John 17 : Jesus' high-priestly prayer -- Immanent and economic Trinity -- Conclusion: The gift of life : knowing the Triune God.