“But if the roof carvings cannot be seen, to whom are their stories being told? Why was such craftsmanship expended on them, and such planning given to their content and narrative? Rose writes: “The most lofty work is as carefully carved and skillfully finished as any at a lower level.”
The best he offers by way of an answer to this mystery is to propose that this care and skill reflect “not just a feeling of self-respect on the part of the sculptor, but a belief that his work was an essential part of the whole building of the church which was for the worship and praise of God.” It seems that communication was not the primary purpose.”
Source: The Christian Science Monitor
See also: Art History Timeline 14-Gothic Architecture, a short lecture with lots of beautiful images from Dr. Jeanne Willette of Otis College of Art and Design on iTunesU. She makes mention at the end of the art made to be seen only by God.