Jaroslav Pelikan, probably the greatest living church historian, has a key point on the heretic’s psychology: “Not the orthodox but the heretics were generally the ones who fastened upon a single idea, which may perhaps have been correct enough in itself, but which blocked the rest of the teaching of Scripture out of view” (Obedient Rebels: Catholic Substance and Protestant Principle in Luther’s Reformation, 1964).
Like dear old Pooh Bear, the heretic has honey on the brain (a very important food stuff, to be sure) but he interprets all of Scripture and reality through that gooey framework. Thus, we find the heretic doing silly things like getting stuck in the entrance to Rabbit’s house, and pretending to be a little black rain cloud.
Of course, this temptation to wear exegetical blinders exists for the orthodox as well, especially for those of us who have recently discovered the (ancient) thrilling doctrines of predestination, infant baptism, or Biblical man and womanhood. The temptation is to focus on one great truth, and forget all the others.
Semper reformanda, but semper middle-of-the-roada!