In Reformed theology, union with Christ is understood to be a comprehensive category that runs through the entire doctrine of Salvation. John Murray observes: "Union with Christ is a very inclusive subject. It embraces the wide span of salvation from the ultimate source in the eternal election of God to its final fruition in the glorification of the elect." Sinclair Ferguson distinguishes six categories of union with Christ. Union with Christ is federal or covenantal in the sense that Christ's obedience is accounted to believers. It is carnal or fleshly in the sense that Christ became incarnate and thus became one with humanity. Union with Christ is also a faith union in which by faith Christians depend on Christ for nourishment. It is a spiritual union because Christians are united to Christ by the agency of the Holy Spirit. 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. It is finally a union of life because Christ lives in Christians and he is visible in their lives. As a step in the order of salvation, union with Christ was seen by John Calvin to be the basis for both justification and sanctification. Alister McGrath notes that while Martin Bucer suggested that justification causes (moral) regeneration, Calvin argued that "both justification and regeneration are the results of the believer's union with Christ through faith." Evangelical Some Evangelicals see union with Christ as a discrete stage in the "order of salvation." The evangelical theologian William Shedd comments "The impartation of Christ's righteousness presupposes a union with him." Robert Dabney, while avoiding deification, said that the bond of the union is the indwelling of the Holy Spirit. Eastern Orthodox Eastern Orthodox theology emphasizes the incarnation as the starting point for our union with Christ. "In Christ God becomes one with us in order to make us one with him; he stooped to take our nature, in order that we might be restored to become partakers of his nature." Theological Content Basis In Christian theology the union of Christ is built on the a priori assumption of Adam's union with humanity (Romans 5:12-21). Also according to the Apostle Paul, Christ's death and resurrection is a prerequisite for believers to be identified with Christ (Romans 6:8-10). In other words, the vicarious death of Jesus is the basis for