"[3] Given the large number of occurrences and the wide range of contexts, the phrase embodies a breadth of meaning.
According to the narrower sense of the phrase, used in Christian theology, union with Christ is a step in the ordo salutis ("order of salvation"), and the basis of the believer's justification.
"[6] Traditional Roman Catholic theology centres the union with Christ in a substantial sense on the unity of the institutional church, past and present.
[8] Medieval conceptions of union with Christ were influenced in large part by mysticism, such as in the preaching of St. Bernard of Clairvaux.
In Reformed theology, union with Christ is understood to be a comprehensive category that runs through the entire doctrine of Salvation.
It is an extensive union in that Christians are united with Christ in everything he has done, including his life, death, burial, resurrection, ascension, and session.
Both the apostle John and Paul employ the Greek preposition eis rather than en in these passages to convey the notion of union with Christ.
Roman Catholic theology holds that believers actually imbibe the physical body and blood of Christ when they partake in the Eucharist.
[23] Evangelical theology contains the idea of an experiential union, where Jesus having gone through life, death and resurrection, shares these experiences with believers.
[24] Both Reformed and Evangelical theology acknowledges that union with Christ is the subjective application of God's objective work in Salvation.