[This post is part of the "Working Week" series.]
Texts are constructed out of words, not ideas, as Mallarmé might say. These 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, which gives the composition its coherence. This purpose 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 yourself being truly creative, not just for the sake of being creative, mind you, but for the sake of finding an elegant solution to the problem of writing, which emerges from the multiplicity of demands to express our ideas in the first place. Because there are so many different reasons to write, it is often a very complex problem. Composition, however, is the simple art of solving it.