I’ll never forget the first time I traveled back to the States after moving to the U.K. Most of the year, London is covered in a blanket of gray gloom, extinguishing incandescence wherever it can be found. But one year I was invited to speak at a conference in Texas. When my plane finally landed, I walked out of the airport and was met by the giddy smile of a prosperous blue sky, its glistening sunshine coating my vitamin D–deficient face. I felt as if I’d been redeemed, brought back to planet earth after a dreary, dispirited exile.
The creation story begins in deep darkness. But then God speaks and suddenly the darkness scatters (Gen. 1:2–3). The New Testament authors were obsessed with this concept of light. Echoing the creation account, both John and the author of Hebrews use light’s radiance to describe the eternal Son’s origin. They give us glistening truths that illuminate our understanding of the eternal relations between the persons of the Trinity.
Light from Light
John opens his Gospel: “In the beginning was the Word. . . . In him was life, and the life was the light of men. The light shines in the darkness, and the darkness has not overcome it” (John 1:1, 4-5). After John announced that the Word had entered the darkness of our forbidden world, he once again used light to announce salvation itself: “The true light, which gives light to everyone, was coming into the world” (v. 9). John is strategic here, preparing us for Jesus’s own declaration: “I am the light of the world. Whoever follows me will not walk in darkness but will have the light of life” (8:12).
Echoing the creation account, both John and the author of Hebrews use light’s radiance to describe the Son’s eternal origin.
The author of Hebrews reminds us that God spoke in former days by the prophets, but in these last days he’s spoken to us by his Son (Heb. 1:2). Returning to the creation story, the author then says this same Son is the One through whom God made the world. Therefore, he must be the “radiance of the glory of God” (1:3). These words are remarkable. The author positions the Son as the “radiance” of God himself. The Son is the same one who “upholds the universe by the word of his power” (1:3). He’s not created by God; he’s the blazing brilliance of divinity.
Lest we subordinate this Son as a lesser glory than the Father, Hebrews changes imagery and says this radiance is the “exact imprint of his [God’s] nature,” a phrase that further establishes the coequality of the Son with the Father. As John Webster wrote, “God’s glory is God himself in the perfect majesty and beauty of his being. The glory is resplendent. Because God himself is light, he pours forth light.” But what does Webster mean when he uses a phrase like “pours forth light”?
Pouring Forth Light
Many church fathers used the language of light to confess the doctrine of the Trinity. Gregory of Nyssa (Against Eunomius 1.39, 2.9) and Basil of Caesarea (Against Eunomius 2.17, 32) taught that the Son is the “resplendent effulgence” of divine glory. They were convinced the biblical imagery of light supported their belief in the eternal generation of the Son.
Eternal generation means the Father communicates the one, indivisible divine essence to his Son from all eternity. To change metaphors from light to birth, the church fathers believed the Son and Father are called by those names because the Son is begotten from the Father’s essence. Yet unlike human birth, the Son is eternally begotten, meaning there never was a time when the Father and Son were not Father and Son. In this way, eternal generation both distinguishes the Son from the Father and ensures the Son’s equality with the Father.
Like the language of light, the language of begetting also comes from Scripture. Back in the opening of his Gospel, John testifies, “We beheld his glory, the glory of the only begotten of the Father” (1:14, KJV). Right there, the apostle mentions glory in the same breath as begetting.
Eternal generation means the Father communicates the one, indivisible divine essence to his Son from all eternity.
That’s why when the fathers defended the Trinity at the Council of Nicaea, they not only confessed the Son as “only-begotten,” but they were also sure to confess him as “Light from Light.” They understood that unless the Son is the radiance of God’s glory, they could not confess him as “true God from true God, begotten not created, of the same essence as the Father, through whom all things came into being.”
God’s Illuminating Image
Once our eyes are opened—or shall we say, illuminated—to the doctrine of eternal generation, we begin to see it everywhere. If John uses the language of begetting, and Hebrews uses God’s radiance, Paul draws our attention to this doctrine by calling the Son “the image of the invisible God” (Col. 1:15), as well as God’s power and wisdom (1 Cor. 1:22–24; cf. Prov. 8:22–30). Yet the imagery of light and glory is not foreign to Paul either: “For God, who said, ‘Let light shine out of darkness,’ has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ” (2 Cor. 4:6). How gracious of God to communicate the grandeur of this great mystery to us by giving us a whole mosaic of biblical concepts that testify to eternal generation in their own way!
Paul’s exclamation reminds us that this doctrine is indispensable for our salvation, a bedrock for the gospel itself. If the Son is not eternally begotten, how can he be sent by the Father to dwell among us and give us new birth? If the Son is not the radiance of God’s glory, how can he descend into our dark world to usher us into his life and light? Unless this Son is the radiance of the glory of God, we have no confidence that the brilliance of his everlasting light will scatter the darkness that leaves us void and empty.
Portions of this article were adapted from Matthew Barrett’s book Simply Trinity: The Unmanipulated Father, Son, and Spirit (Baker, 2021).