Real question. The more I try and find answers about the Holy Ghost the less cohesive it becomes. I am not asking about current spiritual practices.
I am asking of it's historical origins and impact. Where did the concept come from? Is it a misrepresentation of a greater theological ideal? Was it an incorporation of a deity or concept from another religion? It seems alternately idolized (Denying it is an Unpardonable Sin.) and completely ignored.
Please and Thank You.
I can answer this for Judaism: there is no Holy Ghost in the religion, the Holy Trinity is not considered monotheism.
Historically, a holy spirit stems from Judaism and was used as a way to explain "God's touch."
For example, the prophets were all "touched by God" through a Holy Spirit. In this understanding, a holy spirit is not a being or an entity. It is God's influence over people, places and things.
This idea evolved with Christianity. Here, The Holy Spirit is God. It is not just his influence or impact. The Holy Spirit is a component of God, much like God the Father and God the Son. Together, these form the trinity.
It isn't proper to view the Father, Son or Holy Spirit as separate beings. They are all components (aspects) of one God.
As for the Holy Spirit's role - I can only speak of Christian teaching. For Christians, the Holy Spirit is the existence of God in each of us. Accordingly, it is the spark that fuels our faith in God and allows us to live faithful and faith-filled lives.