So a co-worker of mine has asked this question and I told him I’m not sure there is an answer to that question but that I would look into it.
I have The Compendium of Faith by St Thomas Aquinas published as Shorter Summa by Sophia Institute I started to read the chapter on the Holy Trinity before being asked this question and having gotten sidetracked need to get back to reading my book.
St Thomas Aquinas talks about how God is essentially the only perfectly fully formed person.
There is God’s self which is perfect and God’s perfect knowledge of His self, and lastly God’s perfect of love of both His self and His knowledge of His self.
I plan to for finish this chapter and would surmise to go to Augustine and Jerome next but does anyone know where and what I should read from those sources?
Lastly can the question be answered?
Do we know why God is a Trinity or is this a mystery only?