In Christ, the uncreated light of God became visible and incarnate. Third, light is laden with information . Extensive formulas are needed to decode light's information. Christ was the light sent from God, full of information for humankind. Fourth, light is impartial .
Light acts in the same way from all points of view.
The speed of light cannot be altered. In the same way, the grace of God is impartial. We cannot add to or take away from the grace of God. Torrance's sermon may seem superficial in some ways, but in the sermon he uses many physical and metaphysical examples to give the sermon a most substantial grounding. There are many fine sermons in print on this text.