The oneness of the Church (Nicene Creed #9)

In this post we continue looking at the marks (identifying characteristics) of the Church as defined in the Nicene Creed. For other posts in the series, click a number: 1, 2, 3, 456, 7, 8, 10, 111213.

As with the other marks of the Church, the Creed presents its oneness as grounded in its union and communion with the Holy Trinity. As noted by Thomas F. Torrance (in his book, The Trinitarian Faith), the Trinity is...
The regulative center to which all the worship, faith and mission of the Church take their shape: from the Father, through the Son and in the Spirit, and to the Father, through the Son and in the Spirit (p263a). 
The Creed thus proclaims a Christ-centered, incarnational (participatory), Trinitarian ecclesiology (doctrine of the Church). T.F. continues:
Everything we say of the Church must be consistent with the consubstantial oneness between the Son and the Father and be an expression of the union and communion between God and man effected in the incarnate life and reconciling work of the Mediator [Jesus Christ]. That is to say, the doctrine of the Church must be expounded in terms of its internal relation and not some external relation, to Jesus Christ, for it is in Christ and his inherent relation to the Father and the Holy Spirit that the essential nature of the Church is to be found (p264).
This vital truth is the heart of Athanasius' biblical doctrine of the Church as the one Body of Christ. Note T.F.'s commentary here:
It is not due to some external relation in moral resemblance to Christ that the Church is his Body, but due to a real participation in him who is consubstantial with God the Father (p265a).
This participation (koinonia, communion) with Christ, which makes us his one Body, "is not one of nature but one of adoption and grace effected through the gift of the Spirit who comes to dwell in us as he dwells in God" (p265b). Thus this union and communion is deeply personal in that it happens within the incarnate person of Jesus himself, who in his dual nature as God and man, has united God and humanity in one person (p266).

Moreover, Jesus...
...Makes our humanity in him partake of the Holy Spirit with which he has been anointed and sanctified as man for our sakes, and thereby unites it through himself with the Godhead... The Church is thus to be regarded as constituting all who are reconciled to God in one body through the Cross and are made one in Christ, united with his humanity in such a way that he now comprises both in himself, their humanity and his own, as 'one new man,' for he is in them as they are in him (p267).
T.F. then emphasizes that the Church is the one Church of Christ only as it...
...Looks away from itself to its objective source and ground in the Godhead, and dwells in the Holy Trinity, for it is in the Father, Son and Holy Spirit that the Church and its faith are rooted and founded.... The Church is truly Church in so far as it dwells in the Holy Trinity and embodies the truth of the Gospel in its empirical life and worship (p268).
The Church's dwelling in the Holy Trinity is in Jesus, who in his representative humanity is the Church (p270). As members of this Church we are given to participate in the one Body of Christ. This participation is actualized through the one faith and one baptism of the Church (see pp269, 278). With this understanding our definition of what constitutes the one Church is being focused. Though all humanity has, via the incarnation, life, death, resurrection and ascension of Jesus, been (objectively) united to Christ, it is not accurate to say that all humanity is the Church. Rather, Jesus himself is the Church and we humans are part of his one Body as we, through the power of the Holy Spirit, personally (subjectively) participate.

Though the Spirit is at work in all people (poured out on "all flesh"), he is sent from the Father and the Son with a particular ministry of sanctification in the lives of those who are participants in the Church.

As T.F. notes...
The Church constitutes the sanctified community within which we may draw near to the Father through the Son and in the Spirit and share in the eternal life, light and love of God himself (p275).
Thus through the communion [koinonia, participation] of the Holy Spirit imparted to it by Christ, the Church is united to Christ as his body (p277).
Through the pouring out of the Holy Spirit upon it, the Church [is] constituted the unique 'place' where access to the Father through the Son [is] grounded in space and time among the nations of mankind (p278).
When we next return to this series on the Nicene Creed, we'll continue exploring these marks of the Church. Next up is the Church's holiness.