Here is a summary of the HS taken from my recent treatise on the subject as it relates to the Trinity.
The Holy Spirit is the divine third Person of the Holy Trinity
The Holy Spirit was joined with Father and Son as one God by Christian writers very early in the first millennium [St. Clement of Rome (c. 95); St. Ignatius of Antioch (d. 107)], but the Holy Spirit did not gain official recognition by the church as being divine and part of the Trinity until Constantinople I. Early Christian theologians in search of a deeper understanding of God’s nature and the works of the Holy Spirit “gradually made more explicit that which was contained only implicitly” in Scripture (Catholic Encyclopedia, 96).
As explained, the Jehovah's Witnesses reject the idea that the Holy Spirit is a Person or hypostasis, and teach that it is nothing more than God’s active force, “likened to electricity, a force that can be adapted to perform a great variety of operations” (Should You Believe, Chapter 8). This interpretation, however, is wrong.
First, it is true that in the Old Testament God’s Spirit is primarily referred to as a power used to create and influence men’s souls and minds like Moses, David or the prophets either temporarily or permanently (Catholic Encyclopedia, 574). It would teach, guide and eventually affect a moral transformation of mankind under the future New Covenant (ibid.). “The OT clearly does not envisage God’s spirit as a person, neither in the strictly philosophical sense, nor in the Semitic sense. God’s spirit is simply God’s power” (ibid.).
In the New Testament, however, the Spirit of God is both a power and a Person (ibid., 575). The Jehovah's Witnesses regard the supporting verses as mutually exclusive - the Spirit must be either a power or a person, and since it can’t be a person it must be a power. However, Scripture read together cannot accept one meaning at the expense of another, so, as indicated in Strong and Vine’s the power is the “Power of the Holy Spirit” (at 162), which is the Spirit of God (Romans 9:8-11 RSV), and Jehovah (or Lord RSV) is the Spirit (2 Corinthians 3:17 NWT). The Holy Spirit is not simply an inert unthinking electrical current flowing from Jehovah God. It is a powerful spirit Person.
“The revelation that the Spirit of God is a Person is gradual” (Catholic Encyclopedia, 575). The majority of NT texts reveal God’s spirit as something, not someone… (ibid.), but “in the Synoptic Gospels [the Trinitarian formula in Mt. 28.19] clearly speaks of the person of the Holy Spirit.” So even though in most cases “the phrase ‘spirit of God’ reflects the OT notion of “the power of God,” as a result of the teaching of Christ, the definite personality of the Third Person of the Trinity is clear” (ibid.).
In the Acts of the Apostles the Spirit’s personality is not overtly demonstrated in the texts although “[t]he statement in Acts 15.28, “the Holy Spirit and we have decided,” alone seems to imply full personality” (ibid., 575). Paul uses the [Greek word for spirit] 146 times. Sometimes it means man’s natural spirit, but more often it signifies the divine sanctifying power (2 Cor 3.17-18; Gal 4.6; Phil 1.19). However, the Trinitarian formulas employed by St. Paul (e.g., 2 Cor 13.13), indicate a real personality” (ibid., 575).
The personality of the Holy Spirit is very obvious in the theology of the apostle John and is “very rich in meaning” (ibid.).
The Holy Spirit is the Spirit of truth (Jn 14.17; 15.26; 16.13; cf. 1 Jn 4.6; 5.6), and “another helper,” the “paraclete” (Jn 14.16). The Spirit is “another” helper because, after Christ’s Ascension, he takes Christ’s place in assisting the disciples, in teaching them all that Jesus himself had not yet told them, in revealing the future to them, in recalling to their minds that which Jesus had taught them, in giving testimony concerning Jesus, and in glorifying Him (14.26; 16.12-16; 15.26; 1 Jn 2.27; 5.6). (Catholic Encyclopedia, 575)
The New Testament contains many additional references to attributes of the Holy Spirit that indicate personality such as “speaking, hindering, desiring [or] dwelling (Acts 8.29; 16.7; Rom 8.9)” (ibid., 575). Granted, taken in and of themselves one should not automatically identify them as personality traits because “the same expressions are used in regard to rhetorically personified things or abstract ideas (see Rom 8.6; 7.17).” However, in light of the above verses that clearly identify the Holy Spirit as a Person, other activities of a personal nature reinforce the fact that the Holy Spirit is a Person, not an impersonal “it” - and most certainly not an electrical current, or a mere “figure of speech.”
Thus, the Person of the Holy Spirit speaks (Acts 28:25), teaches (John 15:26), strives with sinners (Genesis 6:3), comforts (Acts 9:31), helps our infirmities (Rom 8:26), is grieved (Eph 4:30) and is resisted (Acts 7:51) (Strong and Vine’s, 95, Supplement).
Secondly, the Jehovah's Witnesses reason that “[t]he Holy Scriptures tell us the personal name of the Father - Jehovah. They inform us that the Son is Jesus Christ. But nowhere in the Scriptures is a personal name applied to the holy spirit” (Reasoning, 407). The weakness in this argument lies in the fact that Scripture does not disclose the personal name of the pre-incarnate Word either (John 1:1) and since Jesus is not an archangel, the Word’s name cannot be Michael as they claim (see section 46 ). In line with the Jehovah's Witnesses’ logic the Word was not a Spirit person either because we don’t know His name (based on their assumption that the Word is completely separate from God), but we know that to be untrue. Neither are we told all of the personal names of all angelic spirit and demonic forces but that does not establish their impersonal natures or prove they don’t exist.
Third, the Jehovah's Witnesses argue further that “Acts 7:55, 56 reports that Stephen was given a vision of heaven in which he saw “Jesus standing at God’s right hand.” But he made no mention of seeing the holy spirit (see also Revelation 7:10; 22:13)” (Reasoning, 407). But this ignores the fact that the Holy Spirit has manifested itself visibly as a dove and flames of fire in the past, and is spirit and unseen to the eye in the unaltered form. Just because we don’t see angels or the Almighty does not mean they don’t exist.
Also, the Jehovah's Witnesses claim, falsely, that the Second Coming of Christ, the parousia, occurred in 1914 A.D. (another theory recently changed in part) and that Jesus is present among us today although invisible. According to their way of thinking then, Jesus is not a person either because he can’t be seen. Remember, God Almighty is an invisible spirit (Colossians 1:15) so the Jehovah's Witnesses should be careful in placing too much literal emphasis on Stephen’s “vision” of God in heaven, or the accompanying Spirit which, after all, is spirit.
Fourth, the personal nature of the Holy Spirit is further illustrated by Jesus’ reference to the Holy Spirit as a “helper” or “advocate” (Greek paraclete) who would teach, guide and speak (John 14:16, 26; 16:13). Even though Jesus used the masculine personal pronoun with reference to the Holy Spirit, the Jehovah's Witnesses claim that Jesus was referring to an “it” when He called the advocate “he” or “him.” They write:
Jesus spoke of the holy spirit as a “helper,” and he said it would teach, guide, and speak. (John 14:16, 26; 16:13) The Greek word he used for helper (pa-ra’kle-tos) is in the masculine gender. So when Jesus referred to what the helper would do, he used masculine personal pronouns. (John 16:7, 8) On the other hand, when the neuter Greek word for spirit (pneumatic) is used, the neuter pronoun “it” is properly employed.
Most Trinitarian translators hide this fact, as the Catholic New American Bible admits regarding John 14:17: “The Greek word for ‘Spirit’ is neuter, and while we use personal pronouns in English (‘he,’ ‘his,’ ‘him’), most Greek MSS [manuscripts] employ ‘it.’
So, when the Bible uses masculine personal pronouns in connection with pa-ra-kle-tos at John 16:7, 8, it is conforming to rules of grammar, not expressing a doctrine. (Should You Believe, Chapter 8)
It should first be noted that since the New American Bible “admits” the Greek word for Spirit is neuter they’re not hiding that fact at all. And what the current New American Bible actually states is that “While it has been customary to use masculine personal pronouns in English for the Advocate, the Greek word for “spirit” is neuter, and the Greek text and manuscript variants fluctuate between the masculine and neuter pronouns” (NAB notes John 14:17). Therefore, there is no grammatical prohibition against referring to the Holy Spirit as “he” or “him” versus “it.” It can be either/or.
A literal rendering of “he” at John 15:26 is “that one” (Greek ekeinos), and should not be translated as a gender-neutral “it.” According to Strong and Vine’s, “ekeinos denotes “that one, that person”; its use marks special distinction, favorable or unfavorable; this form of emphasis should always be noted;…” (Strong and Vine’s, 80). Thus, the Jehovah's Witnesses have it backwards. The “it” is a “he” or a “him,” a Person, not the other way around.
This is further illustrated by 1 John 2:1, which the Jehovah's Witnesses forgot to bring to your attention in their publication “Should You Believe in the Trinity?” There, John refers to Jesus as an advocate/helper or paraclete also. It provides in relevant part “And if anyone sins, we have an advocate (paracletos) with the Father, Jesus Christ the righteous” (Green’s Literal Translation).
Thus, both Jesus and the Holy Spirit are referred to as advocate/comforter/helper (paraclete) yet according to the Jehovah's Witnesses’ rules of grammar Jesus is not a person but a gender-neutral “it.” For that matter, Jehovah who can’t be proven to be male or female would also be an “it” although clearly personified as “Him” and “Father” throughout the Bible. That goes for angels as well who, though being gender-neutral are similarly regarded as spirit persons, not electrical currents. The Holy Spirit is the paraclete, the advocate, the counselor and comforter, and in the relevant context a “Person” (hypostasis); the third Person of the Holy Trinity.
Fifth, 1 Corinthians 2:10, 11 illustrates a distinctiveness of the Holy Spirit compared to God (though not independent of God), and an intellectual ability to probe the thoughts of God, something a current of electricity is most likely not capable of doing.
For the Spirit searches everything, even the depths of God. For what person knows a man’s thoughts except the spirit of the man which is in him? So also no one comprehends the thoughts of God except the Spirit of God.