What do Trinitarians believe?
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“the throne of you the God” [is] to the age of the age and the sceptre of righteousness [is] the sceptre of the kingdom of you. Hebrews 1:8. Interlinear.
If Jesus were THE TRUE GOD, that would mean His Father would not be THE ONE TRUE GOD, because THE ONE TRUE GOD cannot have a TRUE GOD, and would instead make TWO TRUE GODS.
As GOD is GOD ALONE, thats what makes GOD the ONE TRUE GOD, which is why there is NO OTHER GOD LIKE THE ONE TRUE GOD.