For it pleased the Father that in him should all fullness dwell;
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Ambrose of Milan
AD 397
With regard to his Godhead, therefore, the Son of God so possesses his own glory that the glory of Father and Son is one: he is not, therefore, inferior in splendor, for the glory is one, nor lower in Godhead, for the fullness of the Godhead is in Christ. .
The fullness is in him and remains in him. This means that he surpasses all things and cannot be surpassed, that he may fashion, refashion, restore the fallen, raise the dead. Thus he says, “Just as the Father has life in himself; so he gives it to the Son to have life in himself.” .
In him it was pleasing, that all fulness should dwell. The greatest plenitude of graces was conferred on him as man, and from him, as he was our head, derived to all the members of his Church. The Protestant translation, followed by Mr. N. by way of explanation adds, it hath pleased the Father; but, as Dr. Wells observes in his paraphrase, there is no reason to restrain it to the Father, seeing the work of the incarnation, and the blessings by it conferred on all mankind, are equally the work of the blessed Trinity, though the Second Person only was joined to our nature. (Witham)
En afterwards the world had attained unto its completion, there came down from above, for causes that we shall afterwards declare, in the time of Herod a certain man called Christ, with a threefold nature, and a threefold body, and a threefold power, (and) having in himself all (species of) concretions and potentialities (derivable) from the three divisions of the world; and that this, says (the Peratic), is what is spoken: "It pleased him that in him should dwell all fulness bodily"
Whatsoever things are of the Father, these he says are of the Son also, and that with more of intensity, because that He both became dead for, and united Himself to us. He said, Firstfruits, as of fruits. He said not Resurrection, but Firstfruits, showing that He has sanctified us all, and offered us, as it were, a sacrifice. The term fullness some use of the Godhead, like as John said, Of His fullness have all we received. That is, whatever was the Son, the whole Son dwelt there, not a sort of energy, but a Substance.
By the term fullness some speak of the Godhead, like as John said, “Of his fullness have we all received.” That is, whatever was the Son, the whole Son dwelt there, not a sort of energy, but a Substance.
Now how will he be proved to have been before all things, who appeared after all things? Who can tell whether he had a prior existence, when he has found no proof that he had any existence at all? In what way also could it have "pleased (the Father) that in Him should all fulness dwell? "