[This post is part of the "Working Week" series.]
If a sentence is an arrangement of words, a paragraph is an arrangement of sentences. There is obviously no grammar of such arrangements but there are some principles to keep in mind. First and foremost, a paragraph should have a unified purpose. This means that all the sentences that are gathered in a paragraph should, at a general level, be about the same thing. They will not, of course, say the same thing, but they will each play a specific role in elaborating, supporting or illustrating a common subject matter. This, in turn, is but one part of the overall subject matter of the text. "The bearing of each sentence upon what precedes," says Grierson (1944: 115), "should be explicit and unmistakable." In an important sense, then, the text's agenda is not advanced (moved forward) within its paragraphs but between them. A paragraph slows down and dwells, as it were, on a particular element of the larger subject covered by the text. Its sentences are arranged with that element clearly in mind.