And this also it behoves us to know, that the names Fatherhood, Sonship and Procession, were not applied to the Holy Godhead by us: on the contrary, they were communicated to us by the Godhead, as the divine apostle says, Wherefore I bow the knee to the Father, from Whom is every family in heaven and on earth. But if we say that the Father is the origin of the Son and greater than the Son, we do not suggest any precedence in time or superiority in nature of the Father over the Son (for through His agency He made the ages ), or superiority in any other respect save causation. And we mean by this, that the Son is begotten of the Father and not the Father of the Son, and that the Father naturally is the cause of the Son: just as we say in the same way not that fire proceeds from light, but rather light from fire. So then, whenever we hear it said that the Father is the origin of the Son and greater than the Son, let us understand it to mean in respect of causation. And just as we do not say that fire is of one essence and light of another, so we cannot say that the Father is of one essence and the Son of another: but both are of one and the same essence. And just as we say that fire has brightness through the light proceeding from it, and do not consider the light of the fire as an instrument ministering to the fire, but rather as its natural force: so we say that the Father creates all that He creates through His Only-begotten Son, not as though the Son were a mere instrument serving the Father’s ends, but as His natural and subsistential force . And just as we say both that the fire shines and again that the light of the fire shines, So all things whatsoever the Father does, these also does the Son likewise. But whereas light possesses no proper subsistence of its own, distinct from that of the fire, the Son is a perfect subsistence, inseparable from the Father’s subsistence, as we have shown above. For it is quite impossible to find in creation an image that will illustrate in itself exactly in all details the nature of the Holy Trinity. For how could that which is create and compound, subject to flux and change, circumscribed, formed and corruptible, clearly show forth the super-essential divine essence, unaffected as it is in any of these ways? Now it is evident that all creation is liable to most of these affections, and all from its very nature is subject to corruption. — Book I, Chapter 8, Concerning the Holy Trinity.