4. And I know not whether the words, “They are one,” are ever found in Scripture as spoken of things of which the nature is different. But if there are more things than one of the same nature, and they differ in sentiment, they are not one, and that so far as they differ in sentiment. For if the disciples were already one by the fact of being men, He would not say, “That they may be one, as we are one,” 606 when commending them to the Father. But because Paul and Apollos were both alike men, and also of like sentiments, “He that planteth,” he says, “and he that watereth are one.” 607 When, therefore, anything is so called one, that it is not added in what it is one, and yet more things than one are called one, then the same essence and nature is signified, not differing nor disagreeing. But when it is added in what it is one, it may be meant that something is made one out of things more than one, though they are different in nature. As soul and body are assuredly not one; for, what are so different? unless there be added, or understood in what they are one, that is, one man, or one animal [person]. Thence the apostle says, “He who is joined to a harlot, is one body;” he does not say, they are one or he is one; but he has added “body,” as though it were one body composed by being joined together of two different bodies, masculine and feminine. 608 And, “He that is joined unto the Lord,” he says,” is one spirit:” he did not say, he that is joined unto the Lord is one, or they are one; but he added, “spirit.” For the spirit of man and the Spirit of God are different in nature; but by being joined they become one spirit of two different spirits, so that the Spirit of God is blessed and perfect without the human spirit, but the spirit of man cannot be blessed without God. Nor is it without cause, I think, that when the Lord said so much in the Gospel according to John, and so often, of unity itself, whether of His own with the Father, or of ours interchangeably with ourselves; He has nowhere said, that we are also one with Himself, but, “that they maybe one as we also are one.” 609 Therefore the Father and the Son are one, undoubtedly according to unity of substance; and there is one God, and one great, and one wise, as we have argued.
5. Whence then is the Father greater? For if greater, He is greater by greatness; but whereas the Son is His greatness, neither assuredly is the Son greater than He who begat Him, nor is the Father greater than that greatness, whereby He is great; therefore they are equal. For whence is He equal, if not in that which He is, to whom it is not one thing to be, and another to be great? Or if the Father is greater in eternity, the Son is not equal in anything whatsoever. For whence equal? If you say in greatness, that greatness is not equal which is less eternal, and so of all things else. Or is He perhaps equal in power, but not equal in wisdom? But how is that power which is less wise, equal? Or is He equal in wisdom, but not equal in power? But how is that wisdom equal which is less powerful? It remains, therefore, that if He is not equal in anything, He is not equal in all. But Scripture proclaims, that “He thought it not robbery to be equal with God.” 610 Therefore any adversary of the truth whatever, provided he feels bound by apostolical authority, must needs confess that the Son is equal with God in each one thing whatsoever. Let him choose that which he will; from it he will be shown, that He is equal in all things which are said of His substance.