It is axiomatic that the Revelation of the Trinity, which is the interior life of God, is not accessible to reason nor logic, by virtue of the fact that man cannot understand God fully, all we can understand (or try to) is what God reveals of Himself to us.
Therefore once the Trinity was made known, by the Incarnation of the Son, man can look back upon his sacred texts and 'see' the evidence therein, he is enlightened, or illumined, but it is wrong to suppose that the Jews could have arrived at a doctrine of the Trinity from their own sacred texts.
Christ said "I and the Father are One" and also "the Father is greater than I" – and together each renders the other either wrong, or illogical ... so that Jesus was either lying, or mistaken ... or He was signifying a Mysery.
In such fashion the Doctrine of the Trinity is never stated explicitly in Scripture, but it is implicit; it is more than simply a 'solution' to the question of the Divinity of the Son, it is a disclosure of the Interior Life of God and it is on this basis that we say 'God is Love' ... not that love is something that God does, but that love is something that God is ... everything flows from that ...
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It should be pointed out that God is Three and One; that the Trinity is not something that 'came about' with the Incarnation, but always was, is, and will be ...
Thomas