In preparing for a class session on prayer I reread this helpful piece by Hoekema. It provides a good reminder of the need for us to have a rich and full understanding of the spiritual benefits of Christ's work.
One of the ways in which the doctrine of union with Christ is helpful is in enabling us to preserve a proper balance between two major aspects of the work of Christ: what we might call the legal and the vital aspects. The Western branch of the Christian church, represented by such theologians as Tertullian and Anselm, tended to emphasize the "legal" side of Christ's work. The aspect of sin these theologians were inclined to stress was guilt, which Christ took away through his atonement, by which he made satisfaction for us and thus paid our debt; the outstanding soteriological blessing was seen as justification; and the most important day on the ecclesiastical calendar was thought to be Good Friday. The Eastern wing of the church, however, represented by such theologians as lrenaeus and Athanasius, was more inclined to stress the "vital" or "life-sharing" side of Christ's work. The aspect of sin these theologians tended to emphasize was pollution, which Christ took away by joining us to himself through .his incarnation; the outstanding soteriological blessing was seen as sanctification; and the most important feast day for the church was Easter. For the Western church, the central boon of the Christian life was deemed to be forgiveness, whereas for the Eastern church it was everlasting life. The Western church tended to accent the Christ who is for us; Eastern church, on the other hand, was more inclined to celebrate Christ who is in us.
We must always keep these two aspects of Christ's work together: legal and the vital, Christ for us and Christ in us. Standing as we doing the Western tradition, we are probably inclined to overstress the legal aspect of our Savior's work and to understress the vital or life-sharing aspect. The doctrine of union with Christ can help us to keep these two facets proper balance. Christ came to earth not just to pay the price for our salvation, as one might pay an overdue bill, but also to bring us into and keep us always in living union with himself. Through union with Christ we receive every spiritual blessing. Christ not only died for us on Calvary’s cross many years ago; he also lives in our hearts, now and forever.
Anthony A. Hoekema, Saved by Grace (Grand Rapids, Mich.:. Eerdmans, 1989), 66-67