We don't make Church "happen." Only Christ can do so. It's his happening.
Let's answer the purpose of the Church by first recognizing what the Church is and how the Church may be identified as God's conservation society. Ascertaining the what and how of the Church greatly factor into the very purpose of the Church; that is, they essentially answer the question why the Church? And, further, why the Church is theologically conservative and necessarily so.
We start with a distinction. Our use of the capitalized word "Church" denotes the "one, holy, catholic, and apostolic Church," as opposed to one's congregation — a "church." So "Church," with a capital "C," denotes the big picture, while "church," with a lower-case "c," demarcates your localized participation in the Church. Additionally, the Church present on Earth should be understood as contiguous with those Christians, those saints, who have died in Christ and whose spirits are with the Risen Lord while their bodies await the resurrection on the Last Day. In other words, although the Church is one, yet it is not entirely manifest as such in the here and now. Still, the dead in Christ are of the Church every bit as much as we who abide in this life.
Now, what is the Church (with a capital "C") as we experience it in this mortal life? Simply put, the Church is Christ manifesting his body through "the assembly of all believers among whom the gospel is preached in its purity, and the holy sacraments are administered according to the gospel" (Augsburg Confession VII:1). This means the Church has a Christological reference, not an anthropological reference. It is less about the activity of people (e.g., assembling and calling themselves a "church") and everything to do with Christ's activities and presence. We neither engender the Church nor self-designate it as such. Simply put, we don't make Church "happen." Only Christ can do so: It's his happening. Consequently, the Church is the result of Christ's creative or manifesting activities by the word of the Gospel.
We don't make Church "happen." Only Christ can do so: It's his happening.
Martin Luther explained it like this: "through the gospel alone the Church is conceived, formed, nourished, generated, instructed, fed, clothed, adorned, strengthened, armed and preserved—in short, the whole life and substance of the Church is in the Word of God." Thus, the Church proceeds from not merely Christ's victory on Golgotha, resurrection from the tomb and ascension, but also from His very being. The Church, then, is the result of divine (Christic) activity within "the assembly of all believers" in which the Son is given in the power of the Holy Spirit as "the gospel is preached in its purity and the sacraments are administered according to the gospel." In this way, the Church is purposed by Christ to be the ark of salvation. The location of Christ for us and as we experience our Lord in the here and now is precisely the Church. In sum, to reappropriate professor David Scaer's maxim: Christology determines ecclesiology: He is the Vine and we, as the Church, are the branches. He is the Temple and we are fitted together in him as a holy habitation of God. He is the head that vivificates the body. Christology determines ecclesiology. That's the first principle of biblical ecclesiology: Christology determines ecclesiology.
Such an orientation advances our understanding of the Church as Christ's self-giving through the Word and Sacraments as not only the means of grace but also the very means by which God the Father, Son, and Holy Spirit articulate and manifest the Church as God's kingdom in this world. The Church, then, is "how" and "where" God's gracious will is "done on Earth as it is in heaven" (Matt. 6:10). Herein, we find the chief purpose of the Church: The Church exists so that the Father would establish, further, preserve and glorify His kingdom on Earth through the reign of the Son within His kingdom people by the power of the Holy Spirit. The Church exists, therefore, as the domain or kingdom of the Triune God's self-giving in love, mercy, grace, truth, and peace. The Church, therefore, is the what, how, where, and why of the Holy Trinity's self-giving for our salvation and sanctification. Hence Saint Cyprian of Carthage's second-century dictum: extra ecclesium nolla salus — "outside of the church there is no salvation." His maxim can and must only be understood with respect to Christ's activity, nothing else. For the Church cannot and does not exist independent of Christ in any way.
The Church exists so that the Father would establish, further, preserve and glorify His kingdom on Earth through the reign of the Son within His kingdom people by the power of the Holy Spirit.
Herein we find yet another purpose of the Church emerging: To vouchsafe the Gospel-boundaried commissioning of water, bread, wine, and duly called and ordained clergy keep the object of faith—Christ—and his word always at center and as the proper object of worship and adoration. In this way, the Church is inherently conservative: It conserves that which begets, preserves, and perpetuates itself — namely the Word of God and the Sacraments of our Lord; it conserves Christology determining ecclesiology. If it does not zealously conserve this, then it cannot exist as the Church (capital "C"). Christ is not present, and it is Christ who, as it were, "performs" the Church. Thus, the Church is inherently theologically conservative and necessarily so. Other competing ecclesiologies may approximate Christianity, but, again, only Christ makes the Church manifest through the pure preaching of the Gospel and the Sacraments administered according to the Gospel. Only Christ makes a thing Christian. Christ actuates the Church, and only he has the power to do so, and he predictably and specifically does so through the full counsel of God and the miracles of the sacraments. So approximation without realization, in this regard, is the loss of all that constitutes the Church as such. That is why the Augsburg Confession says that it is enough to have unity or identification of the Church through these two essential marks of the Church: the pure preaching of the Gospel and the Sacraments administered according to the Gospel. These marks entail and envelop the conservation of other distinguishing marks like antiquity, unity, and liturgy. To have the pure Gospel is to have apostolic antiquity. To have the sacraments according to the Gospel is to have unity. To have these things together is to have the ancient, unifying liturgy as the vehicle by which the Lord brings us himself through the Church. And, so, the Church and her Lord are identified through the conservation of Christ's self-proclamation and accompanying miracles.
Without the necessary conservation of Christ's means of grace codified in the New Testament, the Church does not perpetuate, nor does it proliferate. Instead, the failure to jealously defend and proclaim the conserved Word of God results in non-Church, which is a human endeavor devoid of the power and presence of God. A dying Church is not a small church or a struggling, shrinking congregation but one without the gospel of Christ and the Christ of the gospel. Faithfulness in conservation is life and salvation. Unfaithfulness is death and damnation, no matter a congregation's association, be it Lutheran, or Roman Catholic, or Anglican. Unity and authenticity can only be found in the defining marks of the Church: the pure preaching of the gospel and the sacraments administered according to the gospel, or in the words of Dr. Arthur A. Just: "Gospel Proclamation and Gospel Miracles."
