Indeed, perhaps this is what it means to be made in the image of God. God is love, and when we reflect the image of that love upon the world, when we reach out to others in love, we imitate God's Trinitarian community. If the church is to be a sign of God, then it must likewise reach outside itself, into the world, in love. Of course, this isn't always easy; often it's tragically hard. Reaching out in love often means opening real wounds and closing real divides.
To be sure, these days the church and the people within her often seem far too content to sit upon their hands and wait for grace rather than reach out into the world and find it. But the paradoxical gift of our Triune God is that our differences are just as often the opportunities for, rather than merely obstacles to, relationship. No matter how difficult or challenging our differences may become, we can proceed with faith in the love of our loving God.
The differences of our world - between left and right, Roman and Reformed, America and Africa, rich and poor - are radical ones indeed. Who could argue otherwise? But these things are no more different than man is from God, or fathers are from sons, or spirits are from humans. No more different indeed than flesh is from bread, or blood is from wine. But God reaches out in love nonetheless and makes real communion from these radical differences, and so should we.
At the very least, this perplexing doctrine of the Trinity teaches us that we needn't understand one another or even God to love both one another and God.We don't need to get it, we just need to do it. Though the people I love most - my wife, my parents, my friends - sometimes confuse and perplex me most of all (just like God does), I love them all nonetheless. And this is something of what we mean when we speak of communion, I think. What we taste therefore at our altar, may we live likewise in the world.