XXVII. You see lights breaking upon us, gradually; and the order of Theology, which it is better for us to keep, neither proclaiming things too suddenly, nor yet keeping them hidden to the end. For the former course would be unscientific, the latter atheistical; and the former would be calculated to startle outsiders, the latter to alienate our own people. I will add another point to what I have said; one which may readily have come into the mind of some others, but which I think a fruit of my own thought. Our Saviour had some things which, He said, could not be borne at that time by His disciples (though they were filled with many teachings), perhaps for the reasons I have mentioned; and therefore they were hidden. And again He said that all things should be taught us by the Spirit when He should come to dwell amongst us. Of these things one, I take it, was the Deity of the Spirit Himself, made clear later on when such knowledge should be seasonable and capable of being received after our Saviour's restoration, when it would no longer be received with incredulity because of its marvellous character. For what greater thing than this did either He promise, or the Spirit teach. If indeed anything is to be considered great and worthy of the Majesty of God, which was either promised or taught.
XXVIII. This, then, is my position with regard to these things, and I hope it may be always my position, and that of whosoever is dear to me; to worship God the Father, God the Son, and God the Holy Ghost, Three Persons, One Godhead, undivided in honour and glory and substance and kingdom, as one of our own inspired philosophers not long departed showed. Let him not see the rising of the Morning Star, as Scripture says, nor the glory of its brightness, who is otherwise minded, or who follows the temper of the times, at one time being of one mind and of another at another time, and thinking unsoundly in the highest matters. For if He is not to be worshipped, how can He deify me by Baptism? But if He is to be worshipped, surely He is an Object of adoration, and if an Object of adoration He must be God; the one is linked to the other, a truly golden and saving chain. And indeed from the Spirit comes our New Birth, and from the New Birth our new creation, and from the new creation our deeper knowledge of the dignity of Him from Whom it is derived.
XXIX. This, then, is what may be said by one who admits the silence of Scripture. But now the swarm of testimonies shall burst upon you from which the Deity of the Holy Ghost shall be shown to all who are not excessively stupid, or else altogether enemies to the Spirit, to be most clearly recognized in Scripture. Look at these facts:—Christ is born; the Spirit is His Forerunner. He is baptized; the Spirit bears witness. He is tempted; the Spirit leads Him up. He works miracles; the Spirit accompanies them. He ascends; the Spirit takes His place. What great things are there in the idea of God which are not in His power? What titles which belong to God are not applied to Him, except only Unbegotten and Begotten? For it was needful that the distinctive properties of the Father and the Son should remain peculiar to Them, lest there should be confusion in the Godhead Which brings all things, even disorder itself, into due arrangement and good order. Indeed I tremble when I think of the abundance of the titles, and how many Names they outrage who fall foul of the Spirit. He is called the Spirit of God, the Spirit of Christ, the Mind of Christ, the Spirit of The Lord, and Himself The Lord, the Spirit of Adoption, of Truth, of Liberty; the Spirit of Wisdom, of Understanding, of Counsel, of Might, of Knowledge, of Godliness, of the Fear of God. For He is the Maker of all these, filling all with His Essence, containing all things, filling the world in His Essence, yet incapable of being comprehended in His power by the world; good, upright, princely, by nature not by adoption; sanctifying, not sanctified; measuring, not measured; shared, not sharing; filling, not filled; containing, not contained; inherited, glorified, reckoned with the Father and the Son; held out as a threat; the Finger of God; fire like God; to manifest, as I take it, His consubstantiality); the Creator-Spirit, Who by Baptism and by Resurrection creates anew; the Spirit That knows all things, That teaches, That blows where and to what extent He lists; That guides, talks, sends forth, separates, is angry or tempted; That reveals, illumines, quickens, or rather is the very Light and Life; That makes Temples; That deifies; That perfects so as even to anticipate Baptism, yet after Baptism to be sought as a separate gift; That does all things that God does; divided into fiery tongues; dividing gifts; making Apostles, Prophets, Evangelists, Pastors, and Teachers; understanding manifold, clear, piercing, undefiled, unhindered, which is the same thing as Most wise and varied in His actions; and making all things clear and plain; and of independent power, unchangeable, Almighty, all-seeing, penetrating all spirits that are intelligent, pure, most subtle (the Angel Hosts I think); and also all prophetic spirits and apostolic in the same manner and not in the same places; for they lived in different places; thus showing that He is uncircumscript.
XXX. They who say and teach these things, and moreover call Him another Paraclete in the sense of another God, who know that blasphemy against Him alone cannot be forgiven, and who branded with such fearful infamy Ananias and Sapphira for having lied to the Holy Ghost, what do you think of these men? Do they proclaim the Spirit God, or something else? Now really, you must be extraordinarily dull and far from the Spirit if you have any doubt about this and need some one to teach you. So important then, and so vivid are His Names. Why is it necessary to lay before you the testimony contained in the very words? And whatever in this case also is said in more lowly fashion, as that He is Given, Sent, Divided; that He is the Gift, the Bounty, the Inspiration, the Promise, the Intercession for us, and, not to go into any further detail, any other expressions of the sort, is to be referred to the First Cause, that it may be shown from Whom He is, and that men may not in heathen fashion admit Three Principles. For it is equally impious to confuse the Persons with the Sabellians, or to divide the Natures with the Arians.
XXXI. I have very carefully considered this matter in my own mind, and have looked at it in every point of view, in order to find some illustration of this most important subject, but I have been unable to discover any thing on earth with which to compare the nature of the Godhead. For even if I did happen upon some tiny likeness it escaped me for the most part, and left me down below with my example. I picture to myself an eye, a fountain, a river, as others have done before, to see if the first might be analogous to the Father, the second to the Son, and the third to the Holy Ghost. For in these there is no distinction in time, nor are they torn away from their connection with each other, though they seem to be parted by three personalities. But I was afraid in the first place that I should present a flow in the Godhead, incapable of standing still; and secondly that by this figure a numerical unity would be introduced. For the eye and the spring and the river are numerically one, though in different forms.
Source: Orations (New Advent)