What this book argues for in today's twenty-first-century church was a hallmark doctrine of old school Presbyterianism of the nineteenth century: the doctrine of the spirituality of the church. Which eschatological approach one uses will affect one's understanding of the nature and practice of missions. Mission creep—the expansion of the church's original objective(s)—is a real concern for the contemporary church, and how one understands eschatology affects one's focus on missions. The mission of the church is narrow (Matt 28:18-20), and the calling of individual believers is broad (Rom 12:1-2). If we fail to make this crucial distinction, the church's mission will lose its biblical emphasis. And if the church's mission is lost, then the authority structure, instantiated in the offices and officers of the church, devolves into illegitimacy, because the church is no longer advancing the kingdom ends she was mandated to do by King Jesus. If the institutional church fails to do this, we will be relinquishing and abdicating and abandoning our most singular and particular and peculiar kingdom of God vocation: the harvesting, gathering, and perfecting of the saints.