Monologion: Chapter 44
BASIC WRITINGS
Thus, just as the individual distinguishing characteristics of each do not admit of plurality, since they do not belong to both of them, so what is common to both keeps its individual unity, even though it belongs wholly to each.
For just as there are not two fathers or two sons but one Father and one Son, since their individual distinguishing characteristics belong to them individually, so there are not two spirits but one, even though the Father is a complete spirit and the Son is also a complete spirit. In virtue of their relations they are opposed in such a way that neither takes on the distinguishing characteristic of the other; in virtue of their nature they are harmonious in such a way that each always has the essence of the other. For in virtue of the fact that one is the Father and the other is the Son, they are so different that the Father is never called the Son and the Son is never called the Father; and in virtue of their substance they are so much the same that the essence of the Son always exists in the Father and the essence of the Father always exists in the Son. For there are not different essences but the same essence, not several* essences, but one essence of both.
Chapter 44 How one is the essence of the other Hence, if we say that one is the essence of the other, we are not straying from the truth but rather emphasizing the supreme unity and simplicity of their common nature. For if we say that the Father is the essence of the Son and the Son is the essence of the Father, we cannot understand this in the same way as when we talk about the wisdom of a man through which the man is wise. For a man cannot be wise through himself; but we do not mean that the Son exists through the Father and the Father through the Son, as if one could exist only through the other in the same way that a man can be wise only through wisdom. For just as the supreme wisdom is always wise through himself, so also the supreme essence always exists through himself. Now the Father is completely the supreme essence, and the Son is also completely the supreme essence.Therefore, the Father exists completely through himself, and the Son also exists completely through himself, just as each of them is wise through himself.
For that essence or wisdom which is the Son is no less perfect simply because he is an essence born of the Father's essence and a wisdom born of his wisdom.
But he would indeed be a less perfect essence or wisdom if he did not exist through himself or were not wise through himself. For it is in no way contradictory that the Son both subsists* through himself and has being from the Father. For just as the Father has essence and wisdom and life in himself, so that it is not through someone else's but through his own essence that he exists, through his own wisdom that he is wise, and through his own life that he lives,