This thesis proposes that Robert W. Jenson's identification of the triune God faithfully describes the persons and being of God. To support this I examine the most basic argument of Jenson's 'Systematic Theology',: that God is freely but truly identified by and with Jesus Christ. This includes discussion of Jenson's starting point, his formal description of the three persons of God, and the theological ontology that this entails. Throughout I argue that Jenson's trinitarian description and theological ontology is rightly controlled by an a posteriori logic of response to the triune God's actual life with and for his people. Central to this is the way that Jenson creatively and courageously uses Jesus Christ's life and person as the controlling criterion of all dogmatic statements about God. Finally, this thesis proposes that Jenson's basic insights are made more exact when Jesus Christ is recognized in his perfect relation with the Father and Spirit before, in and after created history. To elucidate this suggestion the nature of the triune God's election and self-determination is reconsidered in light of Jenson's critical insight that the persons are mutually, not identically, perfect in deity. This in turn leads to a brief description of the eternity and freedom of the triune conversation that begins and ends with the Word who is Jesus Christ.