The Biblical Trinity Does not Violate Monotheism

The three persons or roles and modes called the Father, Son and Spirit are reflection and roles of one God. Trinitarian doctrine is not monolithic; that is, there are differing interpretations among Christians. There is definitely some controversy as to the meaning of personhood when using the term persons for the Trinity. Although the multipersonal nature of the one God has been well established in the Hebrew scripture without any controversy, the topic became controversial after the advent of Christ, and the heathens may have contributed a lot in obscuring and corrupting the true trinity that the overall scripture reveals. Here is a good study series by the top Christian philosopher on the trinity:

Unfortunately, the doctrine of the Trinity is often obscured by Christians in mystery. We are very often told that the doctrine of the Trinity is incomprehensible, that it is above logic, that it is something we only grasp by faith and it is inherently mysterious. I think that that is actually selling the doctrine of the Trinity short. The doctrine of the Trinity is not the logical contradiction that three Gods are somehow mysteriously one God. That would in fact be a contradiction. Nor is the doctrine that three persons are somehow one person. That would also be a contradiction. Rather, the doctrine of the Trinity states that there are three persons in one God or, alternatively, that the one God who exists has three centers of self-consciousness – the Father, the Son, and the Holy Spirit. There is really nothing even at face value contradictory about that. It doesn’t say three persons are one person, or that three Gods are one God. Rather, it says that the one God is three persons and there is nothing even apparently logically contradictory about that doctrine.

The doctrine of the Trinity is a systematic summary of the scriptural data concerning the Father, the Son and the Holy Spirit. It doesn’t really matter that the word “Trinity” is not found in the scriptures as such. Any word could be coined to label this doctrine just so long as it is faithful to the scriptural data. And I think that the classical doctrine of the Trinity does express what the scriptures teach.

To study the detailed scriptural background on the Trinity, this website is the best source comprising the Jewish roots of Christianity, also see the trinity page.

The Holy Spirit is the spiritual and invisible aspect of God. The nature of God is defined as a spirit as opposed to physical idol or flesh. The Holy Spirit is ascribed to both God the father and the Son, since they both have the same spirit.

[Isa 63:9-10 NHEB] ⁹In all their affliction he was afflicted, and the angel of his presence saved them: in his love and in his pity he redeemed them; and he bore them, and carried them all the days of old. ¹⁰But they rebelled, and grieved his holy Spirit: therefore he was turned to be their enemy, and he himself fought against them.

Acts 16:7 When they had come opposite Mysia, they tried to go into Bithynia, but the Spirit of Jesus did not allow them.

Phil 1:19 For I know that this will turn out for my deliverance, through your petition and the supply of the Spirit of Jesus Christ,

[Eph 3:14-17 NHEB] ¹⁴For this cause, I bow my knees before the Father, ¹⁵from whom every family in heaven and on earth is named, ¹⁶that he would grant you, according to the riches of his glory, that you may be strengthened with power through his Spirit in the inner person; ¹⁷that Christ may dwell in your hearts through faith; to the end that you, being rooted and grounded in love,

(Utley commentary) - 3:14-17 "Father. . .Spirit. . .Christ" Notice the work of the Trinity as in Eph. 1:3-14. It is true that the term "Trinity" is not used in the NT. However, there are numerous passages where the three divine persons are mentioned in a unified context (cf. Matt. 3:16-17; 28:19; John 14:26; Acts 2:33-34,38-39; Rom. 1:4-5; 5:15; 8:9-10; 1 Cor. 12:4-6; 2 Cor. 1:21-22; 13:14; Gal. 4:4-6; Eph. 1:3-14, 17; 2:18; 3:14-17; 4:4-6; 2 Thess. 2:13; Titus 3:4-6; 1 Pet. 1:2; Jude 1:20-21).

Being the Son of God, Jesus, in the form of a servant always pointed all to his father (as one true God), which does not contradict the worship and equality of the Son; he was never distinct and separated from his father. Just as there is only one Truth, the Spirit of God is also one, because God is only-one in mono-theism.

Jesus says, that God the Father is a Spirit, yet Paul says there is one Spirit. How do trinitarians understand who or what the Holy Spirit is?

The essential elements on the Holy Spirit may be resumed in the following propositions:

• The Holy Spirit is the Third Person of the Blessed Trinity.

• Though really distinct, as a Person, from the Father and the Son, He is consubstantial with Them; being God like Them, He possesses with Them one and the same Divine Essence or Nature.

He proceeds, not by way of generation, but by way of spiration, from the Father and the Son together, as from a single principle. - Holy Ghost

Who is the Holy Spirit?

The Third Person of the Blessed Trinity

This heading implies two truths:

• The Holy Ghost is a Person really distinct as such from the Father and the Son;
• He is God and consubstantial with the Father and the Son.

The first statement is directly opposed to Monarchianism and to Socinianism; the second to Subordinationism, to the different forms of Arianism, and to Macedonianism in particular. The same arguments drawn from Scripture and Tradition may be used generally to prove either assertion. We will, therefore, bring forward the proofs of the two truths together, but first call particular attention to some passages that demonstrate more explicitly the distinction of personality. - Holy Ghost

The term Trinity is employed to signify the central doctrine of the Christian religion — the truth that in the unity of the Godhead there are Three Persons, the Father, the Son, and the Holy Spirit, these Three Persons being truly distinct one from another. For non-Trinitarianism to understand the concept of understanding the Trinity they must start with understanding what we mean by spirit, personality and person.

In Theology, the uses of the word are various. In the New Testament, it signifies sometimes the soul of man (generally its highest part, e.g., "the spirit is willing"), sometimes the supernatural action of God in man, sometimes the Holy Ghost ("the Spirit of Truth Whom the world cannot receive"). The use of this term to signify the supernatural life of grace is the explanation of St. Paul's language about the spiritual and the carnal man and his enumeration of the three elements, spirit, soul, and body, which gave occasion to the error of the Trichotomists (1 Thessalonians 5:23, Ephesians 4:23).

Matter has generally been conceived as in one sense or another the limitation of spirit. Hence, finite spirits were thought to require a body as a principle of individuation and limitation; only God, the Infinite Spirit, was free from all admixture of matter. Thus, when we find the angels described as asomatoi or auloi, in the writings of the Fathers, this properly means only that the angels do not possess a gross, fleshly body; it does not at all imply a nature absolutely immaterial. Such Scripture expressions as "bread of angels", "they shall shine as the angels", as well as the apparitions of these heavenly beings, were adduced as proofs of their corporeality. So speak Sts. Ambrose, Chrysostom, Jerome, Hilary, Origen and many other Fathers. Even in Scholastic times, the degree of immateriality that belongs to finite spirits was disputed. St. Thomas teaches the complete simplicity of all spiritual natures, but the Scotists, by means of their famous materia primo prima, introduced a real composition, which they conceived to be necessary to a created nature. As regards the functions of spirits in the world, and their active relations to the visible order of things, Scripture abounds in instances of their dealings with men, chiefly in the character of intermediaries between God and His servants. They are the heralds who announce his commands, and often too the ministers who execute His justice. They take a benevolent interest in the spiritual good of men (Luke 15:10).

A compact diagram of the Trinity, known as the "Shield of Trinity". The Shield is not generally intended to be a schematic diagram of the structure of God, but it presents a series of statements about the correlation between the persons of the Trinity. - Trinity (Wikipedia)

The Roman Catechism teaches that the Holy Spirit "proceeds from the divine will inflamed, as it were, with love" (I,9.7). The biblical name of the third Person, "Holy Spirit" (pneuma = wind, breath, principle of life), designates a principle of activity. An act of will is an inclination to some known good.

Theologians have given a name to that type of proceeding, calling it "spiration," from the noun "spirit" which, of course, means "breath." We have a good indication of this in St. John's Gospel in Ch. 20:20-23. After his resurrection when Jesus appeared to his Apostles, St. John says "he breathed on them" (v. 22) and then gave them the power to forgive and to retain sins.

The term "spiration" designates the loving activity between the Father and the Son which results in the term of their love, namely, the Holy Spirit. So they say that the Holy Spirit proceeds from the Father and the Son through spiration. This doctrine was taught clearly by the Second Council of Lyons in 1274. - The One and Triune God

Trinitarians understand God to be three persons.

Simply put, Trinitarians understand God to be three persons (the Father, the Son, and the Holy Spirit) with one nature. The Father is God, the Son is God, and the Holy Spirit is God - and there is only one God.

Moreover, only one of the persons of God (the Son) has a physical body - the other two are immaterial beings. Only one of those two is the Spirit, though, and that's the context that Paul is talking about. He's talking about the Church and the indwelling of the Holy Spirit, and only the Holy Spirit is involved in that.

Moreover, he's saying that there's only one Holy Spirit, who dwells within every Christian and every holy space it inhabits simultaneously. It's not an angel; there isn't a host of Holy Spirits assigned to each individual Christian and church.