...And He is the radiance of God's glory and the exact representation of His nature...(Hebrews 1:3)
As we have read previously, the author of the epistle to the Hebrews deifies Christ by establishing His role in creation and by declaring Him the "radiance of [God's] glory" (Hebrews 1:2-3). Yet, the writer continues to expound the nature of Christ, for conjoined to this latter proposition is one of the most definitive expressions of Jesus' divinity in the entire epistle: Jesus is "the exact representation of [God's] nature" (1:3, NASB). This phrase is rendered into English multiple ways in a variety of translations, each proclaiming the same truth, that Jesus: "is the express image of [God's] person," "is the exact imprint of [God's] nature," "bears the very stamp of [God's] nature," or is "the very image of [God's] substance" (1:3, KJV/NKJV; 1:3, ESV; 1:3, RSV; 1:3, ASV). Interestingly, the differences in wording are reminiscent of the historical development of some important theological terms, terms that saints of old took great care to formulate in order to most accurately represent the relationship(s) between the God, the Father, the Son, and the Holy Spirit.
Though the orthodox position traces back to first generation Christians (and, crucially, to Scripture), disagreement concerning the Person of Christ culminated in the fourth century with what is often termed the Arian Controversy/Heresy. Because of the uniqueness of Christ, many were divided (as people still are today) with respect to how to more or less "categorize" Him in terms of ontology. That is, we can make an ontological distinction between God and non-God, between God and God's creation. Within the latter of these categories we can further distinguish between, for example, angelic beings and human beings (among other things). Those who knew Christ on the earth were wholly convinced of His humanity; they had physically "heard," "seen" and "touched" Him (1 John 1:1). Yet they were additionally assured of His simultaneous other-than-humanness. Jesus is the only-begotten Son of God who is better than the angels (cf. John 1:14, 18; 3:16, 18; 1 John 4:9; Hebrews 1:2-5). A pressing question immediately arose in the early church, one that we do well to consider today: Who is Jesus the Christ?
In the early part of the 4th century A.D., under an attempt to preserve the "unicity of God," Arius brought "trinitarian speculation" to a head, denying the deity of all but the Father (Davis 1983:61). At the Council of Nicaea, Bishop Athanasius of Alexandria (pictured at right) opposed Arius with what would come to be adopted as the biblically affirmed catholic faith in regard to the Person of Christ: Christ shares, and is, the same being as the Father. Eventually, the terms that developed to maintain a proper and biblically-founded Christology were "hypostasis" (cf. Hebrews 1:3) and "being/essence (ousia)" in the East, and "person" and "substance" in the West. Using a modified philosophical term, Athanasius confirmed that Jesus was "one in being (homoousia)" with the Father, and this confession is preserved in the Nicene Creed, which states:
We believe in one God,
the Father, the Almighty,
maker of heaven and earth,
of all that is, seen and unseen.
We believe in one Lord, Jesus Christ,
the Only Son of God,
eternally begotten of the Father,
God from God, Light from Light,
true God from true God,
one in Being with the Father
As a result, the orthodox view of the early church affirmed that God exists in three hypostases but one being (ousia), in three Persons but one substance.
Returning to the epistle to the Hebrews, we see its author maintaining the same Christology: Jesus Christ is "the exact representation of [God's] nature," "the exact imprint of [God's] nature," "the very image of [God's] substance" (Hebrews 1:3, NASB, ESV, and ASV). Although we may be tempted to dismiss such discussion as too abstract, we find concrete relevance of this eternal truth in the ability of the Incarnate God to bring about our salvation, as Jesus is He who "made purification for our sins" (1:3).
Davis, L.D. (1983). The First Seven Ecumenical Councils (325-787): Their History and Theology. Collegeville, MN: Liturgical Press.