Teachers are often understandably at a loss when require to correct
students' written compositions. First, there is often no clear dividing line
between coherent and incoherent text, as there typically (or at least often) is
between grammatical and ungrammatical sentences. A text in which surface
lexical or grammatical cohesion is faulty may often seem unclear or in bad
style, rather than obviously "wrong". Second, our intuitions about grammatical
well fonnedness have been sharpened by two thousand years of
explicit syntactic study. Comparably explicit work on discourse organisation
is only now starting to appear. (For a detailed discussion of how far the
concept of well formedness applies to discourse, see Stubbs, 1983b, Chapter
5.)