Did you notice the big blue circle that is bigger than the church in the missional view? Although the church as an institution may be one of the agents and instruments of the Missio Dei, it is not the only agent or instrument. On this view, the mission of God is being advanced not only through the church as an institution but also through the cultural activities of Chistians in the broader world.
The Missional Manifesto (of which Tim Keller is one of the architects) fleshes out what it means to be “missional” in terms of transforming the culture. That document calls on the church and Christians to be “agents of reconciliation” who are “leaders in deeds of justice and ministry to the poor, as well as live out the implications of their faith in business, the arts, in politics, the academy, the home, and in all of life.” This mandate follows from the assumption that “God’s mission ... universally encompasses every aspect of life: personal, familial, social, cultural, and economic” (there’s the big blue circle again).
It is clear that the missional philosophy rests on a Kuyperian philosophy of “Christ the transformer of culture” (to use Richard Niebuhr’s typology) rather than on the “two kingdoms” theology which is more consistent with biblical already/not-yet eschatology. The missional philosophy blurs the distinction between the holy kingdom of God and common grace realm, between cult and culture, between the holy and the common.
That is why, as a Klinean, I am unable to jump on the missional bandwagon. People probably know that I have been a strong critic of theonomy and Christian Reconstructionism, which is essentially the same problem, albeit wedded to a rightwing political philosophy. But Kuyperianism is wrong whether its rudder is tilted to the right or to the left. In the OPC, I was besieged by the Kuyperians of the right. Now that I am in the PCA, I am confronted by the Kuyperians of the left. Kuyperians to the right of me, Kuyperians to the left of me. Who will join me in affirming that “here we have no lasting city, but we seek the city that is to come” (Heb 13:14)?