The essence of the trinity matter is that the trinity doctrine says that the Holy Spirit is a completely separate third person as distinguished from Christ. The problem with this definition is that Ellen White says:
1) The Holy Spirit is a third person of the Godhead.
2) The Holy Spirit is the Life, Breath and Soul of Christ.
The presents a most unusual puzzle that is solvable. The above definitions "appear" contradictory. They are not. Interpreting these two statements about the Holy Spirit, so that nothing contradicts, is the essence of the issue. This can be done. By the grace of God, I have done it.
Succinctly put, this is the solution:
1) The Holy Spirit became a distinct third person, when the ETERNAL SPIRIT of God the Father and God the Son, became the Successor to Christ's first estate of Being, at His Incarnation.
2) The Holy Spirit is the Life, Breath and Soul of Christ, which He sacrificed in the heavenly sanctuary, at His Incarnation, as a gift to be held in trust until His glorification, at which time that gift of His Divine Nature was to be given to us.
The trinity doctrine does not teach this all important sacrifice of Christ which bestows on us the greatest gift that Christ could have given us. This sacrifice was necessary as a regenerating agency, and without this sacrifice the Atonement would have been of no avail. Since the trinity doctrine does not deal in this very personal sacrifice of Christ, but attributes the Holy Spirit to an entirely separate and distinct from Christ third person, such a doctrine makes the sacrifice of Christ of no avail, because it was His LIFE, BREATH AND SOUL, that was the regenerating agency, and not that of a third, separate person.
"The Spirit was given as a regenerating agency, and without this the sacrifice of Christ would have been of no avail." E.G. White, Review and Herald, May 19, 1904, The Promise of the Spirit, pr. 3,
This is why the third person Holy Spirit and Christ must be the same person, with the one SUCCEEDING THE OTHER as the representative of Christ, after He was cumbered with humanity FOREVER.