Martin Luther and the joyful exchange between Christ and his Christian: Implications for the doctrine of justification and the Christian life

This dissertation is a work of systematic theology, supported strongly by historical theology. Its themes of justification and the Christian life and its conclusions, handled largely within a Lutheran historical and contemporary context, are also meant for the larger Christian conversation.;We begin with the question of works: what does God require of God's children that they should be saved? Lutherans agree that justification is a free gift of God, imputed to the believer through faith. But how does the justified Christian become, through this event, someone who freely and joyfully engages in sacrificial works of love on behalf of the neighbor?;In Martin Luther's 1520 treatise The Freedom of a Christian he describes justification as both a declaration (forensic) and a real union (effective), in which a divine marriage and joyful exchange of righteousness for sinfulness takes place between Christ and the believer. This is possible because of the prior exchange, the communicatio idiomatum, between the two natures of Christ. In the Christian life, a third exchange takes place: the Christian takes on the sins and troubles of her neighbor, giving to the neighbor the goodness that she has received from Christ. Thus justification unfolds as sanctification: the two are a dynamic and eschatological unity.;I posit that a model of real, mystical and personal union between Christ and the believer, and through the believer, with the world, must be based neither on substance metaphysics nor on existential relational ontology. It must preserve the human individual and the "alien" nature of Christ's gift of righteousness, and also the doctrine of simul iustus et peccator , righteousness and sinfulness as total and simultaneous states of being. A successful model is trinitarian, perichoretic, and eschatological.;The cosmic basis of union with Christ is participation in the dynamic and essentially related life of the Trinity. The nature of the union is perichoretic, in which Christ inheres and indwells in the believer and is truly present, without loss of individuality. Finally, union with Christ confers the eschatological gifts of justification and sanctification, a perfect state of being that, in this life, is always coming-to-be.