1 John 5.20 – Christ is not the true God?

I'm not trying to disprove or prove anything here.

I know that cannot be done either way with this scripture.

I am merely pointing out that this is a bad scripture to base something like this on, since it can so easily be understood in more than one way.

“We are in union with the true one, by means of his Son Jesus Christ. THIS is the true God and life everlasting.”

Who is “THIS” referring to?

You think that the demonstrative pronoun “this” (hou′tos) refers to its immediate antecedent, Jesus Christ.

But some believe that the most natural reference of hou′tos is to the subject not locally nearest but dominant in the mind of the apostle–God.

Haupt makes a good point: “A testimony to the one true God seems more in harmony with the final warning against idols than a demonstration of the divinity of Christ.”

Even A Grammatical Analysis of the Greek New Testament, published by Rome’s Pontifical Biblical Institute, states: “[Hou′tos]: as a climax to [verses] 18-20 the ref[erence] is almost certainly to God the real, the true, [in] opp[osition to] paganism (v. 21).”

Often hou′tos, generally translated “this” or “this one,” does not refer to the immediately preceding subject of a phrase. Other scriptures illustrate the point. At 2 John 7, the same apostle and penman of the first letter wrote: “Many deceivers have gone forth into the world, persons not confessing Jesus Christ as coming in the flesh. This [hou′tos′] is the deceiver and the antichrist.” Here the pronoun cannot refer to the closest antecedent—Jesus. Obviously, “this” refers to those who denied Jesus. They collectively are “the deceiver and the antichrist.”

The apostle John wrote: “Andrew the brother of Simon Peter was one of the two that heard what John said and followed Jesus. First this one [hou′tos] found his own brother, Simon.” (John 1:40, 41) It is evident that “this one” refers, not to the last person mentioned, but to Andrew. At 1 John 2:22, the apostle uses the same pronoun in a similar way.

Luke makes similar use of the pronoun, as seen at Acts 4:10, 11: “In the name of Jesus Christ the Nazarene, whom you impaled but whom God raised up from the dead, by this one does this man stand here sound in front of you. This [hou′tos′] is ‘the stone that was treated by you builders as of no account that has become the head of the corner.’” The pronoun “this” clearly does not refer to the man who was healed, though he is the one mentioned just before hou′tos. Certainly, “this” in verse 11 refers to Jesus Christ the Nazarene, who is the “cornerstone” on which the Christian congregation is founded.—Ephesians 2:20; 1 Peter 2:4-8.
Acts 7:18, 19 also illustrates the point: “There rose a different king over Egypt, who did not know of Joseph. This one [hou′tos] used statecraft against our race.” “This one” who oppressed the Jews was, not Joseph, but Pharaoh, the king of Egypt.

Such passages confirm the observation made by Greek scholar Daniel Wallace, who says that for Greek demonstratives, “what might be the nearest antecedent contextually might not be the nearest antecedent in the author’s mind.”