Chesed, this oneness teaching is contrary to several clear verses in Scripture saying how the Father is God, the Son is God and the Holy Spirit is also God, yet the Son is NEVER the Father, the Father is NOT the Son, and the Holy Spirit is neither of the other two. All three are real, and all three are Divine, and yet there is only ONE Divine Being. this idea confused christians (and still does Jews and Muslims) for about 400 years from the time of the Apostles. first let me offer my analogy for the one God, three Persons idea:
To better understand the Trinity, think of 3 sunbeams shining on a partially cloudy day. Each are of the same source, same substance, but illuminating different areas.. they are all of the same thing, yet distinct from one another.. So it is with God..>one BEING< one substance, but apparent in 3 PERSONS: Father, Son and Holy Spirit.