[It is now time to put the paragraphs I've written over the last two "working weeks" together into two five-paragraph essays. Here's the first. After putting the individual posts together, I have done some light copy-editing. I will do some more editing over the next couple of weeks.]
Composition is the art of constructing texts. In his classic handbook, Rhetoric and English Composition, Herbert Grierson (1944) points out that this can be understood on three levels: the construction of sentences, paragraphs and whole texts. But he also emphasizes the relation between these levels. Not only is the "the ideal paragraph" essentially "an expanded sentence" (115), the work should always be guided by the same principles. At all levels, "coherence and the right distribution of the emphasis as determined by the purpose you have in view" are paramount (135). There is a sense in which style is just your "choice of words". Composition demands that we put words together, in sentences, paragraphs, and texts, to achieve a well-defined goal.
In a sentence, words are put together grammatically in your attempt to mean something by them. In isolation, words don't mean anything very specific; they do not convey a clear meaning. In fact, until a group of letters is positioned among other words, it is unclear even what language it belongs to. The word "hat", for example, refers to something you wear on your head in English but is a form of the verb "to have" in German. A word really only finds its meaning in the context of a sentence, and here its meaning is determined by usage. Usage is the governing principle of grammatical correctness (Grierson 1944: 94) and that is why the way you construct your sentences goes such a long way towards defining your style. What is often called "accepted usage" by grammarians and editors determines the effect that particular words have in particular combinations and in particular settings. The style of your composition, as you try to get the words to mean what you want to say, is your struggle with what usage (in your particular context) would have your words mean before you started using them. This struggle takes place first and foremost within the sentences you write.
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.
Ultimately, a composition consists of a series of paragraphs. If you looked only at the topic sentences (usually the first sentences) of these paragraphs, you should get a good sense of how the text is organized and what it wants to accomplish. When writing a text, it can therefore be useful to generate an outline simply by listing these topic sentences and perhaps to organize them further using what will turn out to be section headings. You will here need to decide what the organizing principle of the text as a whole will be: a narrative plot, a logical argument, a call to arms, a set of impressions, etc. "It is," says Grierson, "an additional satisfaction if in an essay or a book you can feel at the end not only that you have derived pleasure from this or that part of the work, or this or that special feature—the language, the character drawing, the thoughts, the descriptions—but that as you lay it down you have the impression of a single directing purpose throughout" (1944: 135). The reader should feel, as Aristotle also said, that there was a reason to begin exactly where you began and end exactly where you ended. The composition of the whole text depends on the way the paragraphs are strung together to achieve this single purpose.
Texts are constructed out of words, not ideas, as Mallarmé might say. Words are arranged into sentences, sentences into paragraphs, and paragraphs into whole compositions. The correctness or rightness of these arrangements depend on their overall effect, that is, their aptness to a single purpose. This purpose, which gives the composition its coherence, makes demands of the text as a whole, and the demands of the text will make demands of the individual paragraphs, which will then pass further demands onto the sentences. It's really like any other construction project: the smaller parts must contribute to the larger whole; they must make themselves useful. It is often in working with the sentences that one discovers the style that is best suited to accomplishing the overall goal, always working under the general constraints of usage. It is also here that you might find a truly creative solution to the problem of writing, which can be a very complex problem because there are so many different reasons to write. Composition, in any case, is the simple art of solving it.