There is, accordingly, a good which is alone simple, and therefore alone un- changeable, and this is God. By this Good have all others been created, but not simple, and therefore not unchangeable. “Created,” I say,–that is, made, not begotten. For that which is begotten of the simple Good is simple as itself, and the same as itself. These two we call the Father and the Son; and both together with the Holy Spirit are one God; and to this Spirit the epithet Holy is in Scripture, as it were, appropriated. And He is another than the Father and the Son, for He is neither the Father nor the Son. I say “another,” not “another thing,” because He is equally with them the simple Good, unchangeable and co-eternal. And this Trinity is one God; and none the less simple because a Trinity. For we do not say that the nature of the good is simple, because the Father alone possesses it, or the Son alone, or the Holy Ghost alone; nor do we say, with the Sabellian heretics, that it is only nominally a Trinity, and has no real distinction of persons; but we say it is simple, because it is what it has, with the exception of the relation of the persons to one another. For, in regard to this relation, it is true that the Father has a Son, and yet is not Himself the Son; and the Son has a Father, and is not Himself the Father. But, as regards Himself, irrespective of relation to the other, each is what He has; thus, He is in Himself living, for He has life, and is Himself the Life which He has.
It is for this reason, then, that the nature of the Trinity is called simple, because it has not anything which it can lose, and because it is not one thing and its contents another, as a cup and the liquor, or a body and its color, or the air and the light or heat of it, or a mind and its wisdom. For none of these is what it has: the cup is not liquor, nor the body color, nor the air light and heat, nor the mind wisdom. And hence they can be deprived of what they have, and can be turned or changed into other qualities and states, so that the cup may be emptied of the liquid of which it is full, the body be discolored, the air darken, the mind grow silly. The incorruptible body which is promised to the saints in the resurrection cannot, indeed, lose its quality of incorruption, but the bodily substance and the quality of incorruption are not the same thing. For the quality of incorruption resides entire in each several part, not greater in one and less in another; for no part is more incorruptible than another. The body, indeed, is itself greater in whole than in part; and one part of it is larger, another smaller, yet is not the larger more incorruptible than the smaller. The body, then, which is not in each of its parts a whole body, is one thing; incorruptibility, which is throughout complete, is another thing;–for every part of the incorruptible body, however unequal to the rest otherwise, is equally incorrupt. For the hand, e.g., is not more incorrupt than the finger