15 Extracts from the 'Refutation and Defence.'
'For never was there a time when God was not a father.' And this he acknowledges in what follows, 'that Christ is for ever, being Word and Wisdom and Power. For it is not to be supposed that God, having at first no such issue, afterwards begot a Son, but that the Son has His being not of Himself but of the Father.' And a little way on he adds on the same subject, 'But being the brightness of light eternal, certainly He is Himself eternal; for as the light exists always, it is evident that the brightness must exist always as well. For it is by the fact of its shining that the existence of light is perceived, and there cannot be light that does not give light. For let us come back to our examples. If there is sun, there is sunlight, there is day. If there is none of these things, it is quite impossible for there to be sun. If then the sun were eternal, the day also would be unceasing. But in fact, as that is not so, the day begins and ceases with the sun. But God is light eternal, never beginning nor ceasing. The brightness then lies before Him eternally, and is with Him without beginning and ever-begotten, shining in His Presence, being that Wisdom which said, “I was that wherein he rejoiced, and daily I was glad in his presence at all times”.' And again after a little he resumes the same subject with the words, 'The Father then being eternal, the Son is eternal, being Light of Light: for if there is a parent there is also a child. But if there were not a child, how and of whom can there be a parent? But there are both, and that eternally.' Then again he adds, 'God then being light, Christ is brightness; and being Spirit, for “God is a Spirit” —in like manner Christ is called the breath, for He is the “breath of the power of God”.' And again, to quote the second book, he says, 'But only the Son, who always is with the Father and is filled of Him that IS, Himself also IS from the Father.'
Source: De Sententia Dionysii (New Advent)