[Campion]

Carefully walk through the Athanasian creed, point by point. Also, Catholic apologist Frank Sheed, in his book "Theology and Sanity," has a explanation of the Trinity which I would summarize thusly:

1. God is love
2. God is perfect in all His attributes in and of Himself, entirely apart from (and prior to) creation
3. Therefore, God is perfect love in and of Himself (etc.)
4. Perfect love implies both a subject (the lover) and an object (the beloved)
5. From all eternity, therefore, God beholds and loves - perfectly - an image or idea of himself; God the Father loving God the Son
6. The love between them is so utterly real that it is also a Divine Person, the Holy Ghost.

Of course it's ultimately a mystery; created intellect cannot perfectly grasp or fully understand the relationships within the Godhead.

[MurphsLaw]

Of course it's ultimately a mystery; created intellect cannot perfectly grasp or fully understand the relationships within the Godhead.

Well that's a little "too" convenient...
Just except developed doctrine then on its own merits- not of the Word of God?
There is no biblical mention or verse of the term "Trinity" or "Triune"...
The Catholic Church developed and formalized that idea along with the Nicene Creed whic is also not cited or to be found in the Bible.

What's next then?
with this sort of doctrinal process not explicitly cited in OT or NT,
why not have a bodily Assumption of The Blessed Virgin Mary then?