1. modern linguistics as a change of paradigms

3. Rhetorical Structure

Consider the following paragraph from the introduction to a 2003 magazine article:
Here is the problem with the college-admissions system. It is a vast and intricate bureaucracy designed to do one thing, and it does that very well; but it is under intense social and economic pressure to do something different—something more or less directly at odds with its supposed goal. The resulting tensions affect everyone involved: The high school guidance counselors who try to steer students toward the right school. The college admissions officers who sort through ever mounting piles of applications to choose an entering class. The college administrators who wonder how many of those accepted will enroll—and how many of them will need financial aid. The parents who contemplate what will be (after housing) the second largest financial outlay of their lives. And, of course, the students themselves.
-The Atlantic Monthly. 11/2003
Just as a phrase is a structured combination of words, this paragraph is a structured combination of phrases. Let's review how this passage uses the kinds of syntactic and morphological structure that we've previously studied to express semantic relations like modification and predicate-argument structure ("who did what to whom").
In the paragraph above, "vast and intricate" modifies "bureaucracy", and "intense" modifies "social and economic pressure." This modification relation is expressed by a structure that we might write down something like this:
(NounPhrase
(Adjective (Adjective vast) (Conjunction and) (Adjective intricate)))
(Noun bureaucracy)))
[Exercise for the reader: how would you draw this structure as a tree?]
STEER is a predicate whose arguments may include an agent (the person or thing steering), a theme (the person or thing that gets steered), and a goal (the path or endpoint of the steering). In the passage above, there is a verb "steer" whose agent is "high school guidance counselors", whose theme is "students", and whose goal is "toward the right school". This predicate-argument relation is expressed by the fact that "steer" is a active verb whose subject is the agent, whose object is the theme, etc. In this case, the subject turns out to be "high school guidance counselors", after we untangle and interpret the syntactic structure (... counselors who try to steer ... ). The same semantic relation might have been expressed by syntactic patterns such as "students being steered by guidance counselors", "the steering of students by guidance counselors", and so on.
When you read and understand this passage, you're parsing the structure of its phrases, and using the results to help you interpret local aspects of the meaning, such as modification and predicate-argument structure.
However, it should be clear to you that there is also a larger-scale structure relating the 11 clauses of this paragraph. We could indicate this structure as follows (I've used line breaks, indentation and square brackets for the structural relations, simplified the language to make it fit more easily on the page, and numbered the clauses for future reference):
[A
(1) Here is the problem with the college-admissions system.
(2) It is a bureaucracy designed to do one thing;
(3) but it is under pressure to do something different
(4) something at odds with its supposed goal.
A]
[B
(5) The resulting tensions affect everyone involved:
(6) Counselors who steer students toward the right school.
(7) Admissions officers who sort through piles of applications.
(8) Administrators who wonder how many will enroll
(9) and how many of them will need financial aid.
(10) Parents who contemplate their second largest outlay.
(11) And, of course, the students themselves.
B]
At the highest level, there are two units: A, there is a problem with college admissions; B, the results affect everyone involved. The first unit explains something about what the problem is; the second units lists the kinds of people affected and something about their roles in the process.
Some of this rhetorical structure involves the relationships of phrases inside sentences, and some of it involves relationships among sentences or groups of sentences. Like syntactic structures, these rhetorical structures usually seem to be "trees" -- that is, successive subdivisions of larger units into smaller ones.
One difference between syntax and rhetoric is scale -- syntax typically operates on a smaller scale, among words or small groups of words inside sentences, while rhetoric works on a larger scale, typically relating clauses, sentences and whole sections of a discourse.
Another difference is function. Syntactic structure mainly expresses semantic relations like modification, predication, quantification and so on. These are key parts of a basic account of "sentence meaning". Rhetorical structure typically expresses pragmatic relations like exemplification, concession, justification, summary and so on, things that are part of "speaker meaning", the way that people use language to inform or entertain or persuade.
For the past century or two, linguists have been much more interested in syntactic structure than in rhetorical structure. As a result, theories of syntax are much better developed and more widely known. However, there are some interesting accounts of rhetorical structure, including a body of work known as RST (for "rhetorical structure theory"). RST postulates a tree structure of rhetorical relationships, analogous to the tree structures of syntactic relationships. (For an interesting debate about whether rhetorical relationships are indeed tree-like, see this weblog post "Discourse: Branch or Tangle?")
Some linguists are skeptical that rhetorical structure is even a well-defined kind of mental representation that is intrinsic to language, of the kind that syntax seems to be. Thus rhetorical structures might simply be useful patterns that speakers and writers sometimes choose to create or borrow, just as architects and painters may choose certain stereotypical ways of arranging their materials.
On this view, it might not turn out to be possible to list all the possible rhetorical structures, or to uniquely and accurately classify every passage in terms of such structures, any more than we can list all possible hand tools, or necessarily classify all the tools that we find into a fixed taxonomy. After all, someone can always invent a new tool, or a tool that combines aspects of several old ones. However, it is still useful to have an inventory of the tools in common use at a given time, and (even if these skeptics are right) an inventory of common rhetorical structures has a similar sort of value.