He is the radiance of the glory of God and the exact imprint of his nature, and he upholds the universe by the word of his power (Heb 1:3).
Commentators are divided on how best to render apaugasma in Heb 1:3. In principle, it could either be rendered actively–denoting radiant light, or passively–denoting reflected light. O’Brien offers a good, if pretty brief, defense of the active sense.
Similar ambiguities affect 2 Cor 4:18. Is it active (producing a reflection), middle (self-reflection), or passive (reflection)?
In think the choice in Heb 1:3 may present a false dichotomy. Let’s work our way to that conclusion by examining some other material.
For now we see in a mirror dimly, but then face to face. Now I know in part; then I shall know fully, even as I have been fully known (1 Cor 13:12).
Some commentators think this involves a distinction between the blurry, distorted image (allegedly) produced by ancient mirrors, and seeing without a distorting medium. However, Senft and Fitzmyer think that’s based on ignorance of ancient mirrors, which could reproduce a fairly good likeness. Fitzmyer and Thiselton think this verse involves a distinction between direct and indirect knowledge. A reflected image involves indirect perception rather than direct perception of the object.
For if anyone is a hearer of the word and not a doer, he is like a man who looks intently at his natural face in a mirror (Jas 1:23).
Here the focus of the metaphor lies, not on indirect perception, but self-perception or self-reflection. Looking in the mirror was a metaphor for self-examination.
Seeing yourself in a mirror is a psychological paradox. It doubles you. Objectifies you. Suddenly, you–the perceptive subject–becomes the object of your own perception.
And before the throne there was as it were a sea of glass, like crystal (Rev 4:6).
A sea of glass would be a huge mirror, reflecting the sky.
No one has ever seen God; the only God, who is at the Father's side, he has made him known (Jn 1:18).He is the image of the invisible God, the firstborn of all creation (Col 1:15).18 And we all, with unveiled face, beholding [or reflecting] the glory of the Lord, are being transformed into the same image from one degree of glory to another. For this comes from the Lord who is the Spirit.4 In their case the god of this world has blinded the minds of the unbelievers, to keep them from seeing the light of the gospel of the glory of Christ, who is the image of God.6 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.18 as we look not to the things that are seen but to the things that are unseen. For the things that are seen are transient, but the things that are unseen are eternal (2 Cor 3:18; 4:4,6,18).
Even though these passages don’t specifically use mirror imagery (although that may be implicit in 2 Cor 3:18), they dovetail very nicely with the notion mirror imagery.
In particular, it’s possible to see someone obliquely who’s out of sight. For instance, if two men are standing in front of a large mirror, with one behind the other, you can see the man behind you in the mirror. Even though your back is turned to him, he is visible in the mirror.
That would suit the contrast between the Father’s invisibility, and the visibility of the Incarnate Son, who mediates the Father in the person of the Son.
In addition to bronze and copper mirrors, you could have makeshift mirrors. When the lighting was right, you could see your reflection in a water basin.
Besides artificial mirrors, the ancients were acquainted with reflective phenomena in nature. A smooth body of water reflected the sky. Likewise, you could see your own reflection in water. In a boat. On the edge of a pond.
However, the natural world also presented more complex reflections. The play of light, rain, and water could produce primary, secondary (double), and tertiary rainbows; stacker (or supernumerary) rainbows; twined rainbows; reflected rainbows; and reflection rainbows. For instance:
Needless to say, Bible writers were quite familiar with rainbows (e.g. Gen 9:13-16; Ezk 1:28; Rev 4:30; 10:1). Keen observers of meteorological phenomena. This raises the possibility that when Scripture uses mirror imagery to illustrate the interrelationship between the Father and the Son, this could be a double reflection, like arranging two mirrors face to face. They mirror each other, in mutual reflection.