If you are an astute reader of Trinitarian theology who can elucidate the fine distinctions between, say, Augustine and Origen or LaCugna and Zizioulas, you may or may not be up on the latest (actually, the only) treatise on the Trinity to capture the popular imagination: a little self-published tome called The Shack.

But you should be. Not because it’s a great book; it isn’t. But because its sales are in the stratosphere. It is loved—fiercely loved—by an astounding number of Christians of all stripes.

The Shack has struck a chord (and spawned a cottage industry of companion texts both favorable and critical) because most people have not learned much about the Trinity from their participation in church life—or at least they think they haven’t. (“Trinity Sunday,” in an odd way, keeps the doctrine of God’s tri-unity remote, exotic, and “special”—something to be observed this one day of the year and expounded upon with clunky analogies).

But the Trinity permeates the church’s life and witness. When we baptize in the name of the Father, Son, and Holy Spirit, we name the Trinity as the church’s “determining reality” (Miroslav Volf). In the Eucharist, the gathered community “incarnates and realizes its communion within the very life and communion of the Trinity” (John Zizioulas). The justice, generosity, and equality we seek to embody in our life together all have their source in the Trinity, in which “none is afore, or after other; none is greater, or less than another; but the whole three Persons are co-eternal and co-equal” (The Athanasian Creed).

People who read Augustine and LaCugna know this. But the people in the pews are reading The Shack. Those who love systematic theology—it’s beauty, order, symmetry—can critique this pop-treatment of the Trinity without breaking a sweat.

But church leaders generally have done a poor job of communicating how it is that, for the Church, everything hangs on the pattern of love-in-communion that exists among Father, Son, and Holy Spirit. The Trinity names the truth of both God’s vulnerability and God’s power–or, rather, that God’s vulnerability is–through the suffering death of the Son–God’s power. And, as Nicholas Lash has said,  the Trinity names “the mystery that constitutes, transforms, and heals the world.”

Until we can communicate this in imaginative, engaging ways—that is, until we’re able to help others see (through worship, preaching, potlucks, sacraments, missions, etc.) that the mutual indwelling of the persons of the Trinity has everything to do with everything we do, people will go elsewhere for their theology; they always do. And while they may find fragments of wisdom and truth (as The Shack surely does contain), they will not know the doctrine’s deep connection to lived discipleship.

And many church leaders will find themselves, every year at this time, dusting off that mysterious relic known as the doctrine of the Trinity, putting it on public display with a few unconvincing analogies, only to happily reshelve it again when the day is thankfully, finally over.

This post is an edited version of one I wrote for bLOGOS last year.