Though I have not yet finished it, John Flett’s book The Witness of God has been riveting. Flett argues that contemporary missio Dei theology is largely plagued by a series of breaches that torpedo a theologically-sound account of the church’s mission. One of those breaches is that which ostensibly exists between God’s saving activity and the world. It is thought that this breach must to some extent exist in order to provide space for the church’s role in redemptive history. If God does literally everything himself in overcoming the ontological and moral gap between himself and fallen creation, then it appears that no significant or meaningful place is left for the church’s involvement.
I have not reached the conclusion of Flett’s own proposal, but my increasingly Torrancean instincts lean immediately toward a possible solution that avoids both the practical Arianism of missio Dei theology and yet gives importance to the church’s role in the fulfillment of the missio Dei, namely the doctrine of the vicarious humanity of Christ. T.F. Torrance, well-known for his strong emphasis on this doctrine, points toward such a solution in his essay on the meaning of order in the church:
Order is the co-ordinating of the life of the Church in its fellowship, worship, and mission in the service of the glory of God. The order of the Church’s ministry is the ordering of its life and work through participation in the obedience of Christ.
(1) In the biblical revelation the whole concept of order is viewed over against disorder and chaos. Apart from the ordering of God’s creative Word the world is without form or void, but into the ordered cosmos there has broken the disorder of sin. It belongs to the very nature of sin to divide, to disrupt, to be anarchic—sin is lawlessness, anomia….
(2) The biblical revelation does not work with a concept of natural law…. There is an order of creation (ordo creationis) but that is not discernible by observing the creation (cursus naturae) but only by observing the creative Will of God. This creative Will of God will restore creation to its lost order, and restore to creation its true form and harmony in the Word of God. That is shadowed forth in the divine law promulgated in the Old Testament….
(3) That new order, the new economy, or rather the eternal Economy of God for His creation, came into the world in Jesus Christ. In the Incarnation the Word of God entered into His own disordered world; the Light shone into the darkness; the divine economy entered within historical and creaturely existence. In other words, the Covenant Will of God broke into our world and is completely fulfilled in Jesus Christ both from the side of God and from the side of man….
(4) In Jesus Christ, therefore, in His Incarnation and in the whole course of His obedience, there has taken place in the divine economy a restoration of alienated man to fellowship with God, a conversion of rebellious humanity to the obedience and love of God. In other words, in the whole human life of Jesus the order of creation has been restored; in the midst of our disordered, sin-disrupted existence, there has been lived a human life in perfect order and proportion to the Will of God….
(5) Order in the new creation is to be regarded as a third dimension…. We are not simply concerned … in the Christian Church with the Will of God in love and grace, and then with the obedience of man in love and fellowship. We are concerned with these two, but with the two as fulfilled and completed in Jesus Christ, in the obedient ordering and perfection of His human life as an oblation of all praise and thanksgiving to God the Creator and Father, and therefore of our sharing in His obedience through the power of the Spirit.
(6) Thus order in the New Testament refers to the concrete ordering of our human life and being in the obedient Humanity of Jesus Christ. All order in the Christian Church is a participation in His obedient Humanity—whether that order be an ordering of its daily life, daily worship, or daily fellowship, or daily mission. The whole of the Church’s life is ordered through participation in the ordered life of Jesus Christ, the New Adam, the Head of the New Creation.
In Torrance’s typically dense and compacted style, he unfolds the biblical narrative in terms of order (creation), disorder (sin), and new order (new creation). This narrative sequence is more complex than this threefold schema would imply as it progresses through election of Israel, the function of the law, the prophetic witness, etc. Nevertheless, it is a helpful summary to the end of “ordering” the church’s missional theology and practice in a “scientific” way, one that faithfully corresponds to the nature of God’s own mission as Father, Son, and Holy Spirit.
In one sense, the ultimate terminus of the biblical narrative is a new creation that is co-extensive with the old, when the kingdom comes and God’s will is done on earth as in heaven. On the other hand, that terminus has already broken into the present — not in extensive but in an intensive way — in Jesus Christ. As Torrance explains, all that the new creation will one day be is now concentrated in Christ. He is the new creation, the new order, the fulfillment of the missio Dei in his very person. Having dealt with our sinful disordering in his death on the cross and having inaugurated the new order in his resurrection from the death, Jesus Christ is not only the God who creates new order from disorder but also the Man who has reached his ordered telos as image-bearer of God. As the incarnate Word, Christ is himself the order commanded by God and the corresponding obedience perfectly enacted by man.
Restated in missional terms, Jesus Christ is not simply the divine agent who accomplishes the missio Dei from the side of God, he is also the human agent in whom the ultimate goal of that missio has been fully realized on the side of mankind. By thinking out missiology in terms of the incarnation, in other words, the missio Dei comes to be understood in a twofold sense: both the saving act that comes from God to humanity as well as the obedient response of humanity to God, including the humanity’s movement from being the receiving object of reconciliation to also being an participating subject in the ministry of reconciliation.
This way of theologizing mission thus puts the vicarious humanity of Christ in center stage. This has the advantage of overcoming the breach between the missio Dei and the world (in the union of God and humanity in the person of Christ) while also giving meaningful place to the church’s role in fulfilling that mission (understood as a participation in the humanity of Christ). It also provides a truly scientific grounding for a theology of mission by establishing the obedient humanity of Christ as the primary criterion by which the church’s mission must be measured. Inasmuch as missiology conforms strictly to the missio Dei manifested in the humanity of Christ, it will be a theologically-sound, biblically-faithful, and practically-fruitful theology of mission. This is in many ways simply another way of saying that the church’s mission must be wholly governed by the gospel.
 T.F. Torrance, Conflict and Agreement in the Church, vol. 2 (London: Lutterworth, 1960), 13-16.