In the New Testament 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.).
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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)