My mind cannot think of a good reason why there are not 3 substances (Father, Son, Holy Spirit) in God.
The reason is (basic I know) this: if there are 3 relations inhereing in God and these relations are all equally substance, then why aren’t there 3 substances -three Gods?
I think the problem is that I don’t understand the concept of relation fully.
FN:
Why; what’s wrong with your mind?
You wont be surprised to find out that the Church has not made a definitive pronouncement on this subject either. So, I’d say that you were in good company!
Anyway, as I recall, the general notion of the Trinity is: three persons of one substance, each subsisting distinct in the self-same divine nature. Three persons of one substance, analogous, in a loose way, to perhaps ice, water, and steam. The words “person” and “nature” were commonly used to refer to the Trinity, and, as time elapsed, the ambiguities prevalent in those words were removed. Nature, for instance, is from the Latin
nasci, which literally means, that which is produced (or born). And, person is from the Latin
persona, which originally referred to the masks worn by Greek or Roman actors on stage. That significance was ultimately transferred to the actors themselves.
Ultimately, the words owned the precise meanings necessary to describe the Trinity - which is still perhaps the most profound mystery known to the Church, and is known, but not fully defined, precisely from Scripture. The rest of the creatures in the universe reveal their various natures by their activities, that is, their movements. E.g., birds fly, fish swim, and the plant is, as someone famous once said, “fixed on its peculiar spot [ordained] to draw nourishment, propagate, and rot.”
Our theologians glean from Scripture and say no more than can reasonably be said.
God bless,
jd