I will try to discuss these questions. I will begin by saying that I think that the idea of the "Trinity" is probably the most preposterous teaching of orthodox Christianity. I'm not sure which is the most preposterous. I've already discussed the eternal torment issue and it is right up in the running. Anyway I will here try to give the scriptural reasons for feeling as I do.
I have heard Billy Graham say "I can't explain the Trinity but I believe it". Actually no one can explain it. A lot of people try. I've copied many pages from the web "explaining the Trinity". Otherwise intelligent people write them. I think language doesn't say the same to them that it does to me. They do try to make the point that one has to be in tune with God to understand it. Therefore those of us that think it is idiotic just aren't in tune with God.
Let's see the Father the Son and the Holy Spirit are one yet they are three. Many words are used to try to make this plausible. If you use enough words some people probably think you must have said something.
Just what does the Bible say? It says, "Jesus was the beginning of the creation of God".Rev.3:14. No matter how many words are used to explain it it still says one thing. That God existed first and that Jesus was the first thing he created. If that is true it shoots down the theory of the Trinity.
According to the Trinity idea the Holy Spirit must be a person. Never mind that the word spirit is used over and over again to speak of something that exists that is not a person. The spirit of the world (1Cor.2: 12), the spirit of truth and the spirit of error (1John 4: 6), the spirit of antichrist (1John 4:3); surely no one thinks these places are speaking of a person. The King James Version of the Bible uses the term "Holy Ghost" many times when it is referring to what the Trinitarians would call the third person of the Trinity. Also it uses the term "Spirit of God" many times. For instance in Mathew the third chapter in verses 11 and 16. In verse 11 the word "Ghost" is used in verse 16 the word "Spirit" is used. Both words are from the same Greek word. Most translations use the word "Spirit" in both places. I think most people understand that the term "Holy Ghost" is a poor translation. Still the doctrine of the Trinity demands that the "Holy Spirit" or "Holy Ghost" is a third person yet one in the Trinity. The term "spirit of God" is used over fifty times in the Bible. In all of those times it seems to mean just that. The spirit or the power of God. I don't know if the Trinitarians believes all of those places are talking about this third person, this Holy Spirit. Common sense says that in all places where either Holy Spirit or spirit of God is used it is referring to the power of God. There is one scripture that we should look at. In John 14: 14 and 16 and in 26 here copied from the KJV, "But the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you". Here the personal pronoun "he" and "him" is used. As far as I know that is the only place that a Trinitarian can look to for the idea that the Holy Spirit is a person. As I understand it the pronoun "it" would satisfy the Greek just as well as "he". The Holy Spirit is not a third person in a trinity of Gods.
We still have John 10: 30, "I and my Father are one". I think this is probably a favorite of a Trinitarian. And yet in Jesus' prayer to the Heavenly Father recorded in John 17 in verses 9,11, 20,and 21 " I pray not for the world, but for them which thou hast given me". "And now I am no more in the world, but these are in the world, and I come to thee. Holy Father, keep through thine own name those whom thou hast given me, that they may be one, as we are". "Neither pray I for these alone, but for them also which shall believe on me through their word; that they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me". Here he asks God to allow his followers then as well as his followers now to be one with him and God as he is one with God. Surely no one believes that all members of the church will be one person with God. Common sense says he is talking about common goals that all share.
I have not discussed John 1:1. "In the beginning was the Word, and the Word was with God, and the Word was God". Many feel this clinches the argument in favor of Trinitarians. We should also read the next verse. In NIV it is, "He was with God in the beginning". This goes along with what he said in his prayer to God in John 17: 5 when he prayed that God would glorify him "with the glory I had with you before the world was". Then in the next verse in the passage we're discussing, 'Through him all things were made; without him nothing was made that has been made". In all of these places it is obvious that there are two identities involved. Jesus obviously was the first creation of God and by him all subsequent creation came. So what do we do with John 1:1. "In the beginning he was with God". How do we explain the part that says, "he was God"?
I think that all recognize that the Greek word "Theos" which is here translated God does not in itself mean Jehovah God. It means a "mighty one". Theos in this passage the first time it is used is preceded by the prefix "ho". This has the significance of saying "the God". The second time it is used it does not have the prefix. This is not shown in the translations. It seems obvious that the Greek makes a distinction between the two Theos'. Anyway that is how I look at it and others I know do the same.
I know that this is a serious question. Many people think that salvation depends on how we see it. I don't think that is true, but I don't mean to belittle anyone's beliefs. I think we all believe that in some way salvation depends on faith in Jesus Christ. It is pretty important to understand who he is. We all look to him as the Son of God. I think it unnecessarily confuses the issue to try to make out that he and God are the same person. In fact I think that it detracts from Christ because it really says he does not exist.
I also understand that some feel that if we believe that Jesus and God are two identities then we believe there are two Gods. We don't of course. It seems plain that God is above all. We read in 1 Cor. 15:27, (NIV)"For he "has put everything under his feet." Now when it says that "everything" has been put under him, it is clear that this does not include God himself, who put everything under Christ". To paraphrase, "God has put everything under Christ's feet but in doing that he himself is excepted". I don't know how language could make things any plainer than this. Also in John 14: 28 Jesus says this in so many words "the Father is greater than I".
Jesus is the Son of God. In the sixteenth chapter of Matthew, Jesus asks his disciples who people were saying that he was, then he asked them "who do you say that I am?" Peter answered, "You are the Messiah the Son of the living God." Peter didn't confuse the issue by saying that he was really God appearing as a man and we know that Peter was right in the answer he gave because Jesus said that he was.
It is interesting to note that one third of the New Testament is made up either of the writings of the Apostle Paul or as in the book of Acts about Paul. With all that is said by him not once did he say anything that could be interpreted to imply that Jesus was really God incarnate. In Acts 20: 27 he did say that he had told them "all the counsel of God". He went on there to warn them that "grievous wolves would enter among them". Also that "men shall arise speaking perverse things to draw away disciples after them". Doesn't is seem that if this "doctrine of the Trinity" is true and so important that salvation depends on it that Paul would have mentioned it? Could it be that this is one of the "perverse things" that he speaks of?
Let's not believe the doctrine of the Trinity just because "everybody does".