Collatio cum Maximino, § 14.
If He is begotten, He is Son: if He is Son, He is the “true Son,” because Only-Begotten. For we also are called sons: He Son by nature, we sons by grace . . . To say that because He is begotten, He is of another nature, is to deny that He is the “true Son.” Now we have the Scripture: “That we may be in His true Son Jesus Christ; He is the true God and Eternal Life.” 2566 Why “true God”? because “true Son” of God. For if He has given to animals this property, that what they beget shall be none other than what they themselves are: man begets man, dog begets dog, and should God not beget God? If then He is of the same substance, why callest thou Him less? Is it because when a human father begets a son, though human beget human, yet greater begets less? If so, then let us wait for Christ to grow as human beings grow whom human beings beget! 2567 But if Christ, ever since He was begotten (and this was not in time but from eternity), is what He is, and yet is less than the Father, at that rate the human condition is the better of the two: for a human being at any rate can grow, and has the property of sooner or later attaining to the age, to the strength of the father; but He never: then how is He a “true Son”?
C. Serm. Arian, sec. 1.529:2567
C. Maximin. i. 5.