Chapter 4 — Part I — Article II (Of the Son of God)
Section 143. Q. What mean in the Creed the words Light of light? A. Under the figure of the visible light they in some manner explain the incomprehensible generation of the Son of God from the Father. When we look at the sun, we see light: from this light is generated the light visible every where beneath; but both the one and the other is one light, indivisible, and of one nature. In like manner, God the Father is the everlasting Light. 1 John i. 5. Of him is begotten the Son of God, who also is the everlasting Light; but God the Father and God the Son are one and the same everlasting Light, indivisible, and of one divine nature.