Is the Holy Spirit Merely One Phase of God?

One huge mistake certain sects make is Modalism. According to the Christian Research Institute, this heresy began in the third century. Men such as Sabellius and Paul of Samosata claimed that God switched modes of being. First, he was God Almighty. Then he became Jesus Christ. After the resurrection, he became the Holy Spirit.

A sect called Oneness Pentecostals claims that God manifested himself in three phases by quoting Matthew 28:19 (Bible in Basic English) which reads, "Go then, and make disciples of all the nations, giving them baptism in the name of the Father and of the Son and of the Holy Spirit:. "

They also claim this idea is expressed in Acts 2:38 (BBE) which says, "And Peter said, 'Let your hearts be changed, every one of you, and have baptism in the name of Jesus Christ, for the forgiveness of your sins; and you will have the Holy Spirit given to you.'"

If this is so, what about the other two members of the Trinity being present at Christ's baptism? Luke 3:22 (KJV) reads, "And the Holy Ghost descended in a bodily shape  like a dove upon him, and a voice came from heaven, which said,  'Thou art my beloved Son; in thee I am well pleased.'" How could God be in three modes at once?

And what about 1 Corinthians 15:27 -28 (KJV) which reads, "For he hath put all things under his feet. But when he saith all things are put under him, it is manifest that he is excepted, which did put all things under him. And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all."

Poof! There goes the Modalism argument. I intend on writing about this and other errant views of the Godhead in a book called You Think You're Going to Heaven? In order to be saved, people need to have a proper understanding about who they've rebelled against and the magnanimous gift Christ offers to wretched sinners like us.