Saffer describes poetics as a complete, "emotionally satisfying" work, and rhetoric as the art of persuasion with "invented arguments." As such it does not manipulate, but interacts with the consumer on equal terms. When the two are combined a "design rhetoric" has been created, which lives in the created moment. And as he suggests, it is fundamentally existential. I might add that the creative dynamic is also phenomenal.
Having just posted on Nobel Fields, I suppose I was in the mood to write again about interaction design. The how of design always leaves me wanting more.