Trinity Sunday.

For western Christians, Trinity Sunday is the week after Pentecost; for eastern Christians it is Pentecost, or part of Pentecost. It’s the day Christians are meant to observe, celebrate, and teach about, the trinity.

God’s a trinity. We know there‘s one God; we know Jesus is God, and Jesus’s Father is obviously also God, and the Holy Spirit is God. Ancient Christians determined even though there are three persons who are God, we still have and recognize only one God, and came up with very basic explanations for the paradox. (And every time we venture beyond these explanations, we either start denying God’s threeness or God’s oneness, so really we oughta just leave it at that.)

Once the ancient Christians made the trinity, or our understanding of it, a doctrine, they incorporated it into their Sunday worship liturgies. Every time Christians gathered together, they’d affirm God is a trinity. They’d sing Gloria Patri/“Glory Be to the Father,” a still-popular hymn; here’s the Anglican Church’s English translation.

Glory be to the Father, and to the Son,

and to the Holy Ghost.

As it was in the beginning, is now, and ever shall be:

world without end. Amen.

Roman Catholics use the same words, but “Holy Spirit” instead of “Holy Ghost.”

Anyway for centuries, there wasn’t a special day for observing the trinity, although every once in a while there was a push for one—which church leadership resisted on the grounds that we observe the trinity every Sunday. Eventually Pope John 22 (reigned 1316–34) ordered a Feast of the Trinity for the Sunday after Pentecost—figuring that was the most appropriate time, ’cause humanity didn’t know God was a trinity till the Spirit descended on Pentecost in the year 33.

So what do Christians do for Trinity Sunday? Mostly just read the Athanasian Creed. Sometimes there are trinitarian prayers in the liturgy; sometimes the pastor preaches about the trinity. That’s about it.

A really minor feast day.

The reason most churches don’t bother doing anything for Trinity Sunday (or even know about it) is because they already observe the trinity. Every church I’ve ever been a part of, puts trinity at the top of their faith statements, and never hesitates to declare God’s a trinity, there’s only one God, and the Father, Son, and Holy Spirit are this one God.

Trinity is one of the first doctrines we learn as new Christians. Mostly because it’s admittedly a weird idea: How can God simultaneously be one and three? And the usual explanation—three persons, one being; three ὑπόστασεις/ypóstaseis, one οὐσία/usía—not three beings; not one person; “person” and “being” doesn’t overlap—usually works on everyone. We get it: God’s three of one thing, and one of another thing, and that makes him one God… yet three. Gotcha.

Any time there’s any question about trinity, church leadership automatically affirms and explains the doctrine. So it’s one of those things Christians really don’t feel the need to question. If we’re not so sure about it, if we feel we don’t entirely understand it… we recognize that’s okay; nobody entirely understands it. And there are lots of things in heaven and earth we don’t entirely understand. Still true though.

But because we affirm trinity on a regular basis, do we need a special day for it? Well, I share the attitude of the ancient Christians: Not really.

I’m not against the idea. If there are Christians who really wanna affirm it good and hard—say, Christians who have a lot of unitarians in their community, and feel because of this they need to step up their affirmations of the trinity—yeah, I get why they’d want to emphasize things. (Although one day in the Christian calendar won’t be enough!) At the same time, if your community is full of unitarians, you should probably look at why this is so: Did somebody teach them falsehoods about trinity? Do they think God has to be uncomplicated and logical according to their understandings of complexity and logic? What God-experiences have they had anyway?—what led ’em to personally believe God’s not a trinity?

Although I gotta remind you: Debating people about doctrine, isn’t gonna share God’s love for them as effectively as loving your neighbor. Priorities, Christians.