Oneness theology teaches that there is only one person in the Godhead whose name is Jesus. Jesus is the Father and the Holy Spirit. Regarding His incarnation, oneness people say that Jesus was in heaven at the same time that He was on earth. Unfortunately, the oneness position presents a serious problem.
In the Garden of Gethsemane (Luke 22:42), Jesus prayed to the Father saying, "Father, if You are willing, remove this cup from Me; yet not My will, but Yours be done." See also, "And he went a little further, and fell on his face, and prayed, saying, 'O my Father, if it be possible, let this cup pass from me: nevertheless not as I will, but as thou wilt'" (Matt. 26:39).
Notice that Jesus says that he has a will, and that the Father has a will. That is two wills: one of the Son and the other of the Father. Furthermore, notice that the wills were in opposition. Jesus did not want to have to go to the cross and endure the suffering, but he submitted not to his own will but to the will of the Father. If this is so, then how can Jesus, who is the Father in flesh (and therefore, they are one person) have two separate and opposing wills on the same subject at the same time?
The response is generally that Jesus was fully a man, and that in his humanity he was not the everlasting Father. But if this is so, then what was Jesus if not God incarnate? If He is not fully God incarnate, then the atonement is void since it isn't God making the sacrifice but a mere man. This is the danger of oneness theology. Ultimately, it denies the true incarnation of God.
Sometimes oneness people say that Jesus had another existence outside His existence as a man because he also was existing as the Father; but this implies that there are two beings since each has its own existence different from the other. Furthermore, the Oneness position would have a will of the Father and a will of the Son which are in opposition to each other--yet they are supposed to be one person? This makes no sense. If the oneness people state that Jesus' flesh was at odds with His own presence as the Father in heaven, then again we have no true incarnation.
The problem with the oneness position is serious, and the fact that Jesus' will was separate from the Father's demonstrates that the Father and the Son are different persons within the Godhead. The oneness people are very wrong.
- If it was the flesh side of Jesus speaking to the divine side of Jesus in heaven, then that denies the true incarnation of God in Christ and invalidates the atonement.