Heresy is best seen as a form of Christian belief that, more by accident than design, ultimately ends up subverting, destabilizing, or even destroying the core of Christian faith.  Both this process of destabilization and the identification of its threat may be spread out over an extended period of time.  A way of making sense of one aspect of the Christian faith, such as the identity of Jesus of Nazareth - an aspect that may initially be welcomed and find general acceptance - may later have to be discontinued on account of the potential damage it is subsequently realized to be capable of causing.

An analogy may help to make this difficult idea clearer.  The Parthenon is widely regarded as one of the architectural wonders of the ancient world.  By 1885, this once-glorious classic Greek building was in an advanced state of decay and was in need of restoration.  Iron clamps and rods were used to hold together the building's great slabs of white marble, originally quarried from nearby Mount Pentelicus.  Yet the restorers failed to realized that iron expands and contracts with changes in temperature, thus placing the stonework under pressure.  More important, they also failed to rustproof the ironwork.  As the iron began to corrode, it expanded, cracking the stones it was intended to preserve.  A measure that was aimed at saving the building thus actually ended up accelerating its decay, requiring future generations to undertake even more radical restoration work than was originally needed.  The correction of critical mistakes is often a costly and time-consuming business; nevertheless, it needs to be done.  Heresy represents certain ways of forumulating the core themes of the Christian faith - ways that sooner or later recognized by the church to be dangerously inadequate or even destructive.  What one generation welcomes as orthodoxy another may eventually discover to be heretical.

While all attempts to put the realities of God into human words will fall short of what they try to represent, some are much more reliable and trustworthy than others....... Heresy lies in the shadow lands of faith, a failed attempt at orthodoxy whose intentions are likely to have been honorable but whose outcomes were eventually discovered to be as corrosive as Nikolaos Balanos's iron clamps.  (page 11)