Proposition #21: Acts 5:3 says that Ananias lied to the Holy Spirit and verse 5 says that he lied to God. So the Holy Spirit must be a Person in the Godhead. [1]
Response: Jesus called the holy spirit the “finger of God;” so the holy spirit is God’s instrument of activity, and the Bible associates God’s spirit with His power. [2] Therefore, the holy spirit should not be regarded as a person, whether as part of a trinity or as a totally separate person; but it is reflective of personality, and that personality is the Father’s. There is one point in trinitarian beliefs with which the monotheist [3] can agree: “The Holy Spirit is of the Father… neither made, nor created, nor begotten, but proceeding ….” Since the holy spirit is a projection of God, lying to it is the same as lying to God.
Also, Jesus, having received from his Father all authority in heaven and earth, has been granted exercise over the holy spirit. He can use it, direct it, distribute it, and communicate through it as he wills. Therefore, the holy spirit can be reflective of his personality as well.
Trinitarians claim to be monotheists, but the details of their doctrine contradict the definition of monotheism since they believe in God the Father, God the Son, and God the Holy Spirit, each one individual and distinct from the other.
[1] Consider this, Peter also said, “Ananias, why has Satan filled your heart to lie… How is it that you have contrived this deed in your heart?” Because of the parallels in Peter’s words here, do trinitarians teach that Ananias is one person of a triune Satan? — Acts 5:3, 4 (RSV) [Prop # 21]
[2] Compare Matthew 12:28 to Luke 11:20; and compare Genesis 1:2 to Jeremiah 32:17; consider Luke 24:49 and Acts 1:8. Notice also the parallelism in Luke 1:35. [Prop # 21]
[3] Monotheism asserts that there is only one God.