In Santiago de Compostela, Spain, the WCC`s Fifth World Conference on Faith and Order (1993) strongly urged the drafting of a statement on the nature and mission of the church. The resulting document, Faith and Order Paper 198, is titled, "The Nature and Mission of the Church: A Stage on the Way to a Common Statement." Of course, the unity of the church lies at the heart of the mission of the Faith and Order Commission-indeed, of the World Council of Churches itself. My paper offers a summary and evaluation of this important document from a confessional Reformed perspective. After summarizing Paper 198, including areas of agreement as well as critique, this paper also engages with approaches to these questions often found in current evangelical discussions of mission. Drawing on distinctively Reformed approaches, the principal argument is that the mission of the church is to execute the marks of the church, which are the same as the keys of the kingdom. There can be no antithesis, therefore, between the church-as-place (defined by its marks of public worship) and the church-as-people (defined by mission). In fact, even the attributes of the church are manifested publicly by these marks. Where the gospel is being preached, the sacraments are being administered, and the officers are caring for the flock, we may be confident that the mission is being executed, the keys are being exercised, and the attributes of "one holy, catholic, and apostolic church" are being exhibited. Preaching, sacrament, and discipline are singled out in the Great Commission and, as we have seen, in Acts 2:42. If these are missing, marginalized, or obscured, there is no office, no charismatic ministry, and no innovative program that can build and expand Christ`s kingdom. God may use many means, but he has ordained these and has promised to work the greatest signs and wonders through them. In this way, the New Jerusalem is seen as an eschatological event-a people united to the Son as his Bride, coming down from heaven. It is not a kingdom that we are building, but one that we are receiving (Heb 12:28). And yet, it is also an enduring city in this passing evil age, a historical institution that, for all of its failures, remains the embassy of grace that Christ is building among the ruins of the City of Man.