What is the ontological Trinity?

Thus we see that there could be no full revelation of God, but through the Son by the Spirit, and thereby of the Father. The full revelation of the one God is only thus - Father, Son, and Holy Ghost. This, this only, is what the one God is, one identity of will and being, so that they are essentially one and one only, yet distinct in willing and acting (and we can distinguish them in willing and acting: hence we commonly speak of persons), yet never willing or acting but in the common will and unity of nature.

Without the Trinity love was not known, righteousness, holiness - the spiritual nature of God and purity as such. That is, He never was revealed as He is and always was. All the true nature of God, that is, what He is, without the Trinity is unknown. The Father wills; the Son quickens whom He will; but because we have separate wills, why necessarily have the Father and the Son? The Spirit distributes to whom He will; but this is not separate from the will of the Father and the Son. They have not the same counsel but one counsel, mind, purpose, thought; yet they act distinctly in the manifestation of that counsel. The Father sends the Son, and the Son the Spirit. Yet when the Son comes, He is not thereby separate from the Father. "The Father that dwelleth in me, he doeth the works." So He casts out demons by the Spirit of God; yet He casts them out. There is unity in all that constitutes oneness when we speak spiritually - not unity as one by arriving at the same things, or union, or by being united, as we are by having only one Spirit dwelling in all, but - by being one in eternal being; so that all else flows from that one will and counsel, yet so as that distinction in action in that will is revealed to us: not distinct will, but distinct willing.

Here in this very majestic declaration of the Oneness of the Godhead, care is taken to state it consistently with the truth afterwards revealed concerning the Three Persons of the Godhead—Father, Son and Spirit. These Three Persons, of one Substance, completely united in thought, will, purpose, counsel, are not three Gods, but One God, not a tritheism, but a Holy Trinity. We cannot understand the mystery of all this, but this truth lies at the very foundation of the Christian faith.

So we must be careful in using the terms, first, second and third Persons in the Trinity, not to think there is any difference in importance. The Father is God; the Son is God; the Spirit is God—the Spirit equal in nature and substance to the Father and the Son. If the three Persons of the Godhead are each of them God, it does not follow that there are three Gods. That were impossible. There can be only one God, supreme and unique. Orthodox Christendom believes in three Persons in the Godhead, yet one God, indivisible and unique—the three Persons in the Godhead with one will, one purpose, each sharing to the full every thought and desire and purpose in the minds of the others. We may not, nay cannot, comprehend this. It is a mystery hidden in the Godhead, yet the Godhead is pleased to reveal Itself as Father, Son, and Holy Spirit.

There are three divine persons: the Father, the Son and the Holy Spirit. Each of them is ‘God’.

For the Son, see questions 2 and 3. For the Father, there are so many references to Him as the ‘God and Father’ (e.g. Eph. 1:3). The Spirit is eternal (Heb. 9:14), omnipresent (Ps. 139:7) and co-equal (‘on the same level with’) the Father and the Son (Mt. 18:19; 2 Cor. 13:13; Rev.1:4).

"For the threefold personality of God does not contradict His unity in any way: it shows the manner or condition of it. There are not three independent units side by side, on a level with each other, each almighty, each eternal, each finding in Himself the source of His own life. The unity of the three blessed Persons is not a similarity of character and qualities and powers … three Beings each of Whom is a God. (Will the reader carefully note the exact language employed here—"a God" not "God." Each is God, but not "a God."). It is true though inexpressible, unity of Three Persons … incapable of existence apart from one another. The life of all three is one and the same life, and it has but one source, not three. The very titles by which They are known to us, imply this. They are not proper names, like those of heathen divinities, but titles of relationship, which involve each other, and would be meaningless alone. Fatherhood is impossible without sonship, and sonship without fatherhood."

God, dwelling in the unapproachable light, is Father, Son and Holy Spirit; a community of essence, a community of moral nature and character, a community of life both in principle and continuous activity — a community of fellowship peculiar to themselves, known only to themselves and enjoyed only by themselves; and that jointly and co-equally. It is an eternal fellowship, abiding, unchangeably the same from everlasting to everlasting, an eternally mutual and reciprocal fellowship.

We are, for example, taught in Matt. 28:19 that Father, Son, and Holy Spirit are comprehended under a single “name.” Though there are three Persons, there are not three names, but one; there are not three "grades," but one Tri-personal Unity.* The Lord also said, "I and the Father are One" (John 10:30); and "The Son can do nothing of Himself save whatever He sees the Father doing"; and "The Father knows Me, and I know the Father" (John 5:19; 10:15). These and other passages teach unity and community of nature between the Father and the Son.

Being One in nature, substance and essential being, they love necessarily the same things and so have the same thoughts, will and purpose about everything, though each having His distinct part in activity and relationship in all that the Triune God does, but always working together in complete unison carrying out one common purpose and will. Thus of Christ, the incarnate Son, we read: "For in Him dwelleth all the fulness of the Godhead bodily." "Believest Thou not that I am in the Father, and the Father in Me? the words that I speak unto you I speak not of Myself: but the Father that dwelleth in Me, He doeth the works." "My Father worketh hitherto, and I work." "And Jesus returned in the power of the Spirit into Galilee." "I cast out devils by the Spirit of God." "Who through the eternal Spirit offered Himself without spot to God" (Col. 2: 9, John 14: 10; John 5: 17; Luke 4: 14; Matt. 12: 28; Heb. 9: 14). Each Person of the Godhead takes part in what He, the incarnate Son, does. (John 1: 14; 1 John 5: 20; 1 John 3: 8).

So if the Son takes a place of apparent subordination to the Father and the Spirit takes a place of apparent subordination to the Son, yet it is apparent only, for in fact, each is willingly doing His own part in conjunction and concert with the other two in carrying out one common purpose and will. All three are coequal in deity, essential in being and nature, but distinct in personality and in eternal unchanging relationship to the other and each having His own part and activity which He willingly does in carrying out one divine plan and purpose. Understand it we cannot, speculate on it we dare not, believe it we must, or else we make the divinely inspired Word of God a lie.