The process of giving a simple explanation or a shortened version of something long and complicated is called putting it “in a nutshell.” There is a cautionary addition to the saying reminding us that the only thing in a nut shell is the nut. The concept of the Trinity is a nutshell explanation and we have to be careful not to pack too much into it.
Perhaps the most influential theologians of all time was Saint Augustine (Nov. 13, 354 – Aug. 28, 430, Bishop of Hippo, present-day Annaba, Algeria). He put a great deal of thought into the concept of the Trinity writing fifteen books on the subject. The main point is that God comes to us as Father, Son, and Holy Spirit. Augustine had seven statements about God: The Father is God. The Son is God. The Holy Spirit is God. The Son is not the Father. The Father is not the Holy Spirit. The Holy Spirit is not the Son. And then Augustine adds one more. There is only one God.
Historically, when people wrote about the Trinity the Latin word “persona” was used; God is three personas in one nature or substance. The word “persona” comes from the theater, referring to masks worn by actors in their roles on stage. Today, we are more likely to use the word “person” which carries with it a more individualistic connotation, but in trinitarian theology the persons are three different characterizations of one dynamic actor.
Herbert O'Driscoll writes, “There has never been an end to our search for images by which to express the mystery of the Trinity. St. Patrick used the shamrock to teach about the Trinity. To him, the shamrock spoke of God as Father, Son, and Holy Spirit. It was a primitive way of teaching, but it is open to question whether we have succeeded in improving upon it. If the Trinity is our way of groping for an expression of the totality of God, then what can be better than to stoop down to the green earth and lift from it an image of God’s truth placed there by God’s own hand?”
Just three quick images: a 3 in 1 God, the personas of an actor and the shamrock. Three nutshell explanations and yet the Nut cannot be contained; God will always be grander than our feeble attempts at comprehension.