Eugene Lowry, in his work The Homiletical Plot and his revision of such work in The Sermon, suggests that the sermon create a sequence of experiences on the part of the hearers that mirrors the experiences of a typical plot form.  The sermon therefore moves from conflict through complication to crisis and finally to resolution.  Lowry’s The Homiletical Plot depicts this design as having the following five sections:  (1) upsetting the equilibrium (i.e., “oops”); (2) analyzing the discrepancy (i.e., “ugh!”); (3) disclosing the clue to the resolution (i.e, “aha!”); (4) experiencing the gospel (i.e., “whee!”); and (5) anticipating the consequences (i.e, “yeah!”).  Just as in a narrative, the climax of the story often arises from a surprising discovery of a new way of looking at things, so too in this sermon the reversal is something unforeseen by the hearers and therefore a surprise or, as Lowry calls it, an “aha!” experience.  If the preacher simply moves from trouble to grace without that element of a surprising turn (an unanticipated viewpoint that is nevertheless coherent to the story), the sermon structure is probably a law/gospel/application structure rather than a Lowry Loop.