Hi First Presbyterian Church,

This Sunday is Trinity Sunday. I sometimes like to talk in detail about the Trinity in my sermon on Trinity Sunday, but I won’t be doing that this week. But because God’s triune nature is such an important aspect of who God is to Christians, I didn’t want to miss the opportunity to write to you about it today.

I’m going to take the risk of getting a little technical today. Hang in here with me.

What makes the persons of the Trinity distinct from one another? We say God is “one God in three persons.” Why isn’t the Trinity three distinct gods, instead of three “persons”? Or, if we look at it from the other perspective: What makes God one, despite having three persons?

I guess the fundamental question I’m asking is: Where do God’s “oneness” and “threeness” begin and end? Believe it or not, there is actually an answer to this question. I should say: Theologians have done their best to provide an answer to this question, and the answer has to do with God’s distinct interactions within himself and God’s interactions with the world. Theologians use Latin phrases ad intra and ad extra to differentiate between these two types of interactions.

Ad intra means “within” or “internally” and refers to the way that the persons of the Trinity (Father, Son, and Holy Spirit) relate to each other.

Ad extra means “outside” or “externally” and refers to the way that the persons of the Trinity relate to everything outside themselves.  

Here’s the bottom line: The primary distinction between the three persons of the Trinity (and the reason Christians even insist that there are three persons instead of just one person) is found in God’s ad intra relationships (i.e., the way that Father, Son, and Holy Spirit relate to each other). The primary characteristic that makes each person unique is as follows: The Father is “unbegotten” (i.e., has no beginning). The Son is “eternally begotten” of the Father (i.e., has an origin in the Father). The Holy Spirit “eternally proceeds” from the Father and the Son (i.e., has an origin in the Father and the Son).

You might be thinking: “What a minute, Aaron! Are you telling me that the Son of God had a beginning?” Yes, I am! But notice that his beginning is described as “eternally begotten.” So, if the Son’s existence originated from the Father, when did the Son come into existence? That’s an invalid question, because he’s always existed. It’s the same for the Holy Spirit who originated from the Father and the Son, and yet has also always existed. See for yourself in the text of the Nicene Creed. This is what Christians have been professing for centuries. This is part of the mystery of the Trinity. The Son and the Holy Spirit have origins that we’ll never find, because they’ve always existed.

Let me see if I can put this another way. Unbegottenness is the unique personal property of the Father; eternal begottenness is the unique personal property of the Son; and eternal procession is the unique personal property of the Holy Spirit. Everything else the persons of the Trinity share with each other. The three persons share the same mind, the same will, the same substance, and even the same actions. What the Father thinks and does, the Son and the Holy Spirt think and do, too. And vice versa.

Does your brain hurt yet? Mine does, too.

Here are some practical take-aways from thinking about the Trinity.

1) In Western “enlightened” thinking, we tend to think in binaries. Good or bad; friend or enemy; true or false; conservative or liberal; Republican or Democrat; white or black. I think, if God’s fundamental nature resists binary thinking (after all, 3=1 is either right or it’s wrong, isn’t it?!), then our thinking ought to resist binary thinking, too. For me, this means I should seek to live my life with humility and with an openness to having my mind changed.

2) If the persons of the Trinity can be distinct from one another and yet work together in mind, will, and action, then we ought to seek to live together the same way. The persons of the Trinity share their life with each other (begetting and proceeding) and yet work together. Let’s do that for each other, too – in humility and love.

Peace to you,

Pastor Aaron