This is in the early part of Sayer’s essay “Toward a Christian Esthetic”:
I will go so far as to maintain that the extraordinary confusion of our minds about the nature and function of art is principally due to the fact that for nearly two thousand years, we have been trying to reconcile a pagan, or at any rate a Unitarian, esthetic with a Christian – that is, a Trinitarian and Incarnational – theology. Even that makes us out too intelligent. We have not tried to reconcile them. We have merely allowed them to exist side by side in our minds; and where the conflict between them became too noisy to be overlooked, we have tried to silence the clamor by main force, either by brutaly subjugating art to religion, or by shutting them up in spearate prison cells and forbidding them to hold any communication with each other.
-Dorothy Sayers, Toward a Christian Esthetic
She goes on to take a stab at defining what art looks at from a “trinitarian” standpoint. I won’t repeat the points here: it would take the space of the entire essay. It’s a good first start I think, but could use a lot of work (and better examples). She admits as such in the beginning. But as for a starting place, I think the diagnosis is correct: the church has never really wrestled with a theology of art. The pagan world has done that for us and we’ve been confused, stuck with their tools and ideas. We’re still confused about it right now.