Today is the feast of St. Ambrose of Milan, Doctor of the Church. From his work On the Holy Spirit (Book II, Chapter 12):
Consider meanwhile whether you can say that the Spirit effects all things which the Father effects; for you cannot deny that the Father effects those things which the Holy Spirit effects; otherwise the Father does not effect all things, if He effects not those things which the Spirit also effects. But if the Father also effects those things which the Spirit effects, since the Spirit divides His operations, according to His own will, you must of necessity say, either that what the Spirit divides He divides according to His own will, against the will of God the Father; or if you say that the Father wills the same that the Holy Spirit wills, you must of necessity confess the oneness of the divine will and operation, even if you do it unwillingly, and, if not with the heart, at least with the mouth.
But if the Holy Spirit is of one will and operation with God the Father, He is also of one substance, since the Creator is known by His works. So, then, it is the same Spirit, he says, the same Lord, the same God. And if you say Spirit, He is the same; and if you say Lord, He is the same; and if you say God, He is the same. Not the same, so that Himself is Father, Himself Son, Himself Spirit...; but because both the Father and the Son are the same Power. He is, then, the same in substance and in power, for there is not in the Godhead either the confusion of Sabellius nor the division of Arius, nor any earthly and bodily change.
The Roman governor of Aemilia-Liguria, whose capital was Mediolanum or Milan, he was only a catechumen when he was forcibly made bishop by the people. Ambrose tried to get out of it, but the Emperor thought he made a great choice for bishop, and he was baptized, confirmed, ordained, and elevated to bishop all in the same week.