Because rhetoric tries to orient the audience toward a worldview, it is imperative for the study of rhetoric to identify and evaluate the controlling ideas (or "god-terms") on which the ethics of any discourse is based.
Ah ha! So I guess this answers my question about the Burke reading. I had a hard time following the Burke, but Weaver's connection to Plato is obviously much clearer. (And Weaver in general is also much clearer.)