Theology of the Trinity

[Phidippides]

How developed is the theology of the Trinity in the Bible, and is it only found in the New Testament?

[skiguy]

I could be wrong, but I don't think it was.  The Holy Spirit wasn't really known to believers until Jesus made it known to them. 

[Donald Baker]

The Trinity still confuses theologians even today.  It is very difficult to pin down just exactly the role of the Holy Spirit is that differentiates it from Jesus and God the Father other than it is the Paraclete or Comforter.

[Phidippides]

The difficulty of understanding the Trinity reminds me of the passage regarding St. Augustine from the Golden Legend:

It was so that this glorious doctor made and compiled many volumes, as afore is said, among whom he made a book of the Trinity, in which he studied and mused sore in his mind, so far forth that on a time as he went by tbe sea-side in Africa, studying on theTrinity, he found by the sea-side a little child which had made a little pit in the sand, and in his hand a little spoon. And with the spoon he took out water of the large sea and poured it into the pit. And when S. Augustin beheld him he marvelled, and demanded him what he did. And he answered and said: I will lade out and bring all this water of the sea into this pit. What? said he, it is impossible, how may it be done, sith the sea is so great and large, and thy pit and spoon so little? Yes, forsooth, said he, I shall lightlier and sooner draw all the water of the sea and bring it into this pit than thou shalt bring the mystery of the Trinity and his divinity into thy little understanding as to the regard thereof; for the mystery of the Trinity is greater and larger to the comparison of thy wit and brain than is this great sea unto this little pit. And therewith the child vanished away.

https://sourcebooks.fordham.edu/basis/goldenlegend/GoldenLegend-Volume5.asp#Augustine

[Donald Baker]

I have to agree with this description.  It is a mystery that we are ill-equipped to understand as we are now.