Regardless of whether a paragraph is deductively or inductively structured, readers can generally follow the logic of a discussion better when a paragraph is unified by a single purpose. Paragraphs that lack a central idea and that wander from subject to subject are apt to confuse readers, making them wonder what they should pay attention to and why.
To ensure that each paragraph is unified by a single idea, Francis Christensen, in Notes Toward a New Rhetoric (NY: Harper & Row, 1967), has suggested that we number sentences according to their level of generality. According to Christensen, we would assign a 1 to the most general sentence and then a 2 to the second most general sentence, and so on. Christensen considers the following paragraph, which he excerpted from Jacob Bronowski's The Common Sense of Science, to be an example of a subordinate pattern because the sentences become increasingly more specific as the reader progresses through the paragraph:
- The process of learning is essential to our lives.
- All higher animals seek it deliberately.
- They are inquisitive and they experiment.
- An experiment is a sort of harmless trial run of some action which we shall have to make in the real world; and this, whether it is made in the laboratory by scientists or by fox-cubs outside their earth.
- The scientist experiments and the cub plays; both are learning to correct their errors of judgment in a setting in which errors are not fatal.
- Perhaps this is what gives them both their air of happiness and freedom in these activities.
Christensen is quick to point out that not all paragraphs have a subordinate structure. The following one, which he took from Bergen Evans's Comfortable Words, is an example of what Christensen considers a coordinate sequence:
- He [the native speaker] may, of course, speak a form of English that marks him as coming from a rural or an unread group.
- But if he doesn't mind being so marked, there's no reason why he should change.
- Samuel Johnson kept a Staffordshire burr in his speech all his life.
- In Burns' mouth the despised lowland Scots dialect served just as well as the "correct" English spoken by ten million of his southern contemporaries.
- Lincoln's vocabulary and his way of pronouncing certain words were sneered at by many better educated people at the time, but he seemed to be able to use the English language as effectively as his critics.