Chapter 5.--Nothing is Spoken of God According to Accident, But According to Substance or According to Relation.
6. Wherefore nothing in Him is said in respect to accident, since nothing is accidental to Him, and yet all that is said is not said according to substance. For in created and changeable things, that which is not said according to substance, must, by necessary alternative, be said according to accident. For all things are accidents to them, which can be either lost or diminished, whether magnitudes or qualities; and so also is that which is said in relation to something, as friendships, relationships, services, likenesses, equalities, and anything else of the kind; so also positions and conditions, [570] places and times, acts and passions. But in God nothing is said to be according to accident, because in Him nothing is changeable; and yet everything that is said, is not said, according to substance. For it is said in relation to something, as the Father in relation to the Son and the Son in relation to the Father, which is not accident; because both the one is always Father, and the other is always Son: yet not "always," meaning from the time when the Son was born [natus], so that the Father ceases not to be the Father because the Son never ceases to be the Son, but because the Son was always born, and never began to be the Son. But if He had begun to be at any time, or were at any time to cease to be, the Son, then He would be called Son according to accident. But if the Father, in that He is called the Father, were so called in relation to Himself, not to the Son; and the Son, in that He is called the Son, were so called in relation to Himself, not to the Father; then both the one would be called Father, and the other Son, according to substance. But because the Father is not called the Father except in that He has a Son, and the Son is not called Son except in that He has a Father, these things are not said according to substance; because each of them is not so called in relation to Himself, but the terms are used reciprocally and in relation each to the other; nor yet according to accident, because both the being called the Father, and the being called the Son, is eternal and unchangeable to them. Wherefore, although to be the Father and to be the Son is different, yet their substance is not different; because they are so called, not according to substance, but according to relation, which relation, however, is not accident, because it is not changeable.
[570] Habitus
Chapter 6.--Reply is Made to the Cavils of the Heretics in Respect to the Same Words Begotten and Unbegotten.
7. But if they think they can answer this reasoning thus,--that the Father indeed is so called in relation to the Son, and the Son in relation to the Father, but that they are said to be unbegotten and begotten in relation to themselves, not in relation each to the other; for that it is not the same thing to call Him unbegotten as it is to call Him the Father, because there would be nothing to hinder our calling Him unbegotten even if He had not begotten the Son; and if any one beget a son, he is not therefore himself unbegotten, for men, who are begotten by other men, themselves also beget others; and therefore they say the Father is called Father in relation to the Son, and the Son is called Son in relation to the Father, but unbegotten is said in relation to Himself, and begotten in relation to Himself; and therefore, if whatever is said in relation to oneself is said according to substance, while to be unbegotten and to be begotten are different, then the substance is different:--if this is what they say, then they do not understand that they do indeed say something that requires more careful discussion in respect to the term unbegotten, because neither is any one therefore a father because unbegotten, nor therefore unbegotten because he is a father, and on that account he is supposed to be called unbegotten, not in relation to anything else, but in respect to himself; but, on the other hand, with a wonderful blindness, they do not perceive that no one can be said to be begotten except in relation to something. For he is therefore a son because begotten; and because a son, therefore certainly begotten. And as is the relation of son to father, so is the relation of the begotten to the begetter; and as is the relation of father to son, so is the relation of the begetter to the begotten. And therefore any one is understood to be a begetter under one notion, but understood to be unbegotten under another. For though both are said of God the Father, yet the former is said in relation to the begotten, that is to the Son, which, indeed, they do not deny; but that He is called unbegotten, they declare to be said in respect to Himself. They say then, If anything is said to be a father in respect to itself, which cannot be said to be a son in respect to itself, and whatever is said in respect to self is said according to substance; and He is said to be unbegotten in respect to Himself, which the Son cannot be said to be; therefore He is said to be unbegotten according to substance; and because the Son cannot be so said to be, therefore He is not of the same substance. This subtlety is to be answered by compelling them to say themselves according to what it is that the Son is equal to the Father; whether according to that which is said in relation to Himself, or according to that which is said in relation to the Father. For it is not according to that which is said in relation to the Father, since in relation to the Father He is said to be Son, and the Father is not Son, but Father. Since Father and Son are not so called in relation to each other in the same way as friends and neighbors are; for a friend is so called relatively to his friend, and if they love each other equally, then the same friendship is in both; and a neighbor is so called relatively to a neighbor, and because they are equally neighbors to each other (for each is neighbor to the other, in the same degree as the other is neighbor to him), there is the same neighborhood in both. But because the Son is not so called relatively to the Son, but to the Father, it is not according to that which is said in relation to the Father that the Son is equal to the Father; and it remains that He is equal according to that which is said in relation to Himself. But whatever is said in relation to self is said according to substance: it remains therefore that He is equal according to substance; therefore the substance of both is the same. But when the Father is said to be unbegotten, it is not said what He is, but what He is not; and when a relative term is denied, it is not denied according to substance, since the relative itself is not affirmed according to substance.