People working in the academic discipline of Rhetoric & Public Affairs occasionally joke about having to explain to their family and friends outside of their profession what it is exactly that they study and or "do." Several answers I've heard are quite straightforward ("I study the history of public address") to those a bit more sophisticated ("I do rhetorical history; I study how speech shapes the progress of cultures and societies") and many variations along the spectrum.
Having studied rhetoric through an undergraduate, masters, and doctorate program (still working on the last) I continue to reflect upon just how "diverse" and sporadic is the field of rhetoric. Many people in the field like it this way, some would prefer more definite boundaries, and others wish for even more diversity and "out of the box" thinking and applications. Of course, for the Christian scholar, there should be a desire and an attempt to integrate rhetoric into its proper relationship to glorifying God.
One of the puritans I've come across in studied for my dissertation sought to relate all of the liberal arts under one overarching philosophy of life, with theology heading them all as the art of living well. Rhetoric was one of the liberal arts, and was defined as the art of speaking ornately, revealing a view of rhetoric as predominantly style, delivery, or eloquence of expression. Dialectic was the art of discoursing well, which essentially meant how to think logically and arrange expression logically. Although some scholar lament taking away from rhetoric the canons of invention, arrangement, and memory (leaving only delivery and style), I think they miss the point of the Ramist approach to the liberal arts, which the Puritans followed (though not always with strict rigidity). It was never Ramus' intent to divorce any one of the liberal arts from the other, but rather to avoid superficial repetitions of content, duplication of methods, and general confusion of terms and their meanings. By streamlining dialectic and rhetoric in the way he did, Ramus was not seeking to take away from rhetoric what was traditionally its own elements, but to organize it in relation to dialectic in such a way that they would operate (with grammar) as true counterparts as Aristotle had originally organized them.
It is true that Ramus and his followers understood dialectic differently than did Aristotle, for while Aristotle distinguished "scientific" discourse (i.e. rigorous logical development from assumed or unquestioned axioms) and "dialectical" discourse (i.e. rigorous logical development from generally believed or well accepted opinions) the Ramist dialectic only sought to consider universal premises that had the status of Aristotle's "scientific" epistemological quality. In other words, opinions had to be argued back to universal and established truths, as opposed to being argued on their own foundations. The perceptive reader will recognize the underlying philosophical assumptions behind these differences. For Aristotle, the epistemological standards were quite different than for Calvinistic Protestants of which Ramus became a convert and whom followed Ramus in his attempts to bring all knowledge and education under the epistemological authority of Christian revelation--the Bible or Word of God and natural revelation as understood through premises set for in that Word.
Rhetoric does not operate apart from dialectic, but rather in coordination with it--in a way not altogether different from Augustine's approach in On Christian Doctrine. In that treatise, Augustine used the tools of rhetoric as a means for interpreting the Scriptures accurately, and then conveying them or arguing them persuasively and clearly to Christians and non-Christian as required. The Puritans allowed the analytical elements of rhetoric to be considered under the head of dialectic, and kept for rhetoric the attention to style, which Augustine treated in book four of his treatise (completed almost a generation after the first three books had been written). Because the truth is given to be discovered in Scripture, the invention and arrangement aspects of rhetoric from the classical approach are more clearly and narrowly circumscribed. One may, but need not, look to human authorities, beautiful literature, or cultural norms to gather materials for persuasion. One needs only to discern what the Scriptures teach and adapt them appropriate to the consciences of the immediate audience. Style and delivery, even for Aristotle, were more closely linked to the psychological considerations of rhetoric--how does this or that rhythm, this or that metaphor, this or that gesture, etc. touch upon, move, or otherwise impact the consciences of the audience? Arguments obviously have this component as well, but on a much more abstract level--since one's first concern is with discerning the truth, or the logical consistency of claims, prior to consideration of how persuasive an audience will find them.
All this is not to say that the Puritans had the right definition and approach to rhetoric. It is open to debate whether or not their divisions accomplished what they hoped for in terms of integrating the liberal arts under theology, or the authority of Scripture. What is of importance for the present concern is that their general philosophy set the agenda for how rhetoric was to be defined. Nothing profound there. What is more interesting, and what will take more time to tease out (my studies remain incomplete and inconclusive) is to what extent proximate aims or emphases (what some rhetorical scholars have called "exigences" and "constraints" of the situation that requires speech for its resolution) remain consistent with the general philosophy, and to what extent their view of rhetoric is affected by, or affects the whole exchange. Does the classical view of Aristotle--that rhetoric is governed by the historical, changing, particular constraints--outweigh the more dialectical approach of the Puritans and later Calvinists I'm studying?
It is a question that may prove uninteresting and fruitless for the larger dissertation, but it does interest me, and aligns with the normative considerations of how we ought to define what is rhetoric.