There certainly was not a time when God was not the...

There certainly was not a time when God was not the Father. Neither, indeed, as though He had not brought forth these things, did God afterward beget the Son, but because the Son has existence not from himself, but from the Father. Being the brightness of the eternal light, he himself is also absolutely eternal. For since light is always in existence, it is manifest that its brightness also exists, because light is perceived to exist from the fact that it shines, and it is impossible that light should not shine. Now this word "I am" expresses his eternal substance. For if he is the reflection of the eternal light, he must also be eternal himself. For if the light subsists forever, it is evident that the reflection subsists forever. And that this light subsists, is known only by its shining; neither can there be light that does not give light. We come back, therefore, to our illustrations. If there is day, there is light; and if there is no such thing, the sun certainly cannot be present. If, therefore, the sun had been eternal, there would have been also endless day. Now, however, as it is not so, the day begins when the sun rises, and it ends when the sun sets. But God is eternal light, having neither beginning nor end. And along with Him there is the reflection, also without beginning, and everlasting. The Father, then, being eternal, the Son also is eternal, being light of light; and if God is the light, Christ is the reflection.— Dionysius (About A.D. 249).