The term ‘union with Christ’ sums up the relationship between Christ and his people.
The church has understood this in various ways.
1. Incarnational union. This view, which was held my many of the early Fathers and continues to be held in the Eastern Orthodox tradition, is that in incarnation God in Christ became one with us in order to make us one with him. He took on our human nature in so that we might partake in his divine nature. The focus of God’s saving work, according to this view, would be Jesus’ birth, rather than his death and resurrection.
2. Union by faith. This view owes much to Martin Luther. We sinners can contribute nothing towards our salvation. Christ, on the other hand, is all-sufficient. This dual emphasis gives the impetus for the exercise of faith, which unites us with Christ as a bride is united with her bridegroom. By faith, our sins are imputed to him, and his righteousness is imputed to us.
3. Covenantal union. The Reformed tradition has tended to see the church’s relationship with Christ in terms of a covenant, which is based on the divine promises and which find their expression in Christ’s work as Mediator. The idea of ‘federal headship is key: just as we share in Adam’s sin and condemnation, so we share by faith in Christ’s obedience and atonement. Priority is given to god’s eternal redemptive purposes, rather than to the temporal response of faith. Indeed, this latter is itself the gift of God.
4. Sacramental union. The Catholic tradition stresses incorporation into Christ through baptism as the outward sacrament of initiation and repentance and faith is its inward appropriation. The Eucharist is the sacrament of continuation in Christ, and enables Christians to grow in him and with one another.
5. Experiential union. Christians have generally understood the life of faith to be not merely a following of Jesus, but an actual participation in his life, death and resurrection. Our old sinful nature has died with him, and we share in the life and power of his resurrection. Empowered by the Holy Spirit, we share Jesus’ status, privileges and suffering, as we are made more like him and prepared for life with him in glory.
6. Spiritual or mystical union. Mysticial, pietist and charismatic traditions often emphasise the conscious experience of union with Christ. This often draws on the love-relationship of bride and groom, and focuses on prayer, meditation, contemplation and worship. The goal is to enjoy free and unrestrained fellowship with Christ.
Drawing on these various perspectives, we might say that union with Christ:
- has its foundations in the loving purpose of a covenanting God;
- is established by the saving ministry of his incarnate Son;
- is entered into through the outward (sacramental) response of an inner trusting faith in the promises of the gospel;
- sanctifies us by transforming us into the likeness of Jesus as the Spirit baptizes us into his life and privileges;
- introduces us to an intimate loving relationship with Christ, and through him to the Father, which we shall experience through time and eternity.
(Based on A.J. Spence, in New Dictionary of Theology: Historical and Systematic, art. ‘Union with Christ’. The final bulleted list is quoted verbatim, although reformatted)