Style: Ten Lessons in Clarity and Grace: Lesson 5

Cohesion and Coherence

Cohesion: Readers must feel that they move easily from one sentence to the next, that each "coheres" with the one before and after.

Coherence: Readers must also feel that sentences are not just individually clear but constitute a unified passage focused on a coherent set of ideas.

Cohesion

Cohesion refers to how a group of sentences "hang together." Sometimes, to achieve better cohesion we have to "violate" other writing "rules" we think are sacrosanct. Take for example the following two sentences:

1. The collapse of a dead star into a point perhaps no larger than a marble creates a black hole.
2. A black hole is created by the collapse of a dead star into a point perhaps no larger than a marble.

Given a choice between these two sentences we would probably choose the first since it uses an active verb while the second uses a passive verb. But the passive does have its uses, such as helping readers create that sense of flow that characterizes a coherent passage. Which of the following two passages "flows" better?

1. Some astonishing questions about the nature of the universe have been raised by scientists studying black holes in space. The collapse of a dead star into a point perhaps no larger than a marble creates a black hole. So much matter compressed into so little volume changes the fabric of space around it in puzzling ways.
2. Some astonishing questions about the nature of the universe have been raised by scientists studying black holes in space. A black hole is created by the collapse of a dead star into a point perhaps no larger than a marble. So much matter compressed into so little volume changes the fabric of space around it in puzzling ways.

The second passage reads more coherently because the concept introduced by each new sentence seems to follow from the previous sentence. This technique is called "old-to-new" and is one of the most important principles of a cohesive writing style. The principles of old-to-new are:

1. Begin your sentences with information familiar to your readers.
2. End your sentences with information your readers cannot anticipate.

Coherence

However, writing can have a cohesive "flow" and be almost indecipherable. Consider the following passage:

Saner, Wisconsin, is the snowmobile capital of the world. The buzzing of snowmobile engines fills the air, and their tanklike tracks crisscross the snow. The snow reminds me of Mom’s mashed potatoes, covered with furows I would draw with my fork. Mom’s mashed potatoes usually made me sick, that’s why I play with them. I like to make a hole in the middle of the potatoes and fill it with melted butter. This behavior has been the subject of long chats between me and my analyst.

This passage is cohesive, moving from Saner to snowmobiles to snow to Mom’s mashed potatoes to behavior, but it certainly is not coherent.

To understand coherence we need to consider how readers make sense out of larger groupings of sentences. Readers feel a passage is coherent when the writer helps them accomplish two tasks:

1. Identify the topics (what the sentence is about) of individual sentences quickly.
2. Recognize how the topics form a connected set of ideas.

Readers want to know what a sentence is about, its topic. However, this is not always easy to find. Consider the following sentences. What are the topics?

1. And therefore, politically speaking, in Eastern states since 1980, acid rain has become a serious problem.
2. International cooperation is still the goal of most countries.
3. It is impossible for your claims to be proved conclusively.
4. In regard to these questions, I believe there is a need for more research.
5. It is likely that our proposals will be accepted.
6. Results like these no one could have predicted.

Topic refers not to the grammatical subject of a sentence, but to its "psychological" subject, and we expect to find the topic in the first few words of the sentence. Readers are more comfortable with these early topics because it helps them understand what the sentence is about. More important, readers depend on seeing in a sequence of topics (in a sequence of sentences) what the whole passage is about.

Combining Cohesion and Coherence

If you begin sentences and even clauses with information familiar to your readers, with phrases that are short, simple, and familiar, your readers are more likely to think you can write clearly and coherently. And no two units of information are shorter and simpler than the subject of a sentence and that subject’s specific actions as a verb.

Try revising the following:

Some sort of palace revolt or popular revolution plagued seven out of eight reigns of the Romanov line after Peter the Great. In 1722, achievement by merit was made the basis of succession when the principle of heredity was terminated by Peter. This resulted in many tsars’ not appointing a successor before dying, including Peter. Ivan VI was less than two months old when appointed by Czarina Anna, but Elizabeth, daughter of Peter the Great, defeated Anna and ascended to the throne in 1741. Succession not dependent upon authority resulted in the boyars’ regularly disputing who was to become sovereign. Male primogeniture became the law in 1797 when Paul I codified the law of succession. But conspirators strangled him, one of whom was probably his son, Alexander I.

Avoiding Illusory Cohesion

This handout lists ways of improving cohesion through providing consistency of topics and by helping the reader see the movement between various ideas. Some writers try to create cohesion by using logical conjunctions like thus, therefore, however, and so on, regardless of whether those words signal any genuine logical connections. Is the following passage cohesive?

Because the press is the major medium or interaction between the president and the people, how it portrays him influences his popularity. Therefore, it should report on the president objectively. Both reporters and the president are human, however, subject to error and favoritism. Also, people act differently in public than they do in private. Hence, to understand a person, it is important to know the whole person, his environment, upbringing, and education. Indeed, from the correspondence with his family, we can learn much about Harry S. Truman, our thirty-third president.

The connectors are virtually meaningless. Experienced writers rely more on the intrinsic flow of their prose than on connecting devices like these. While you might need a but or however when you contradict or qualify what you have just said, and a therefore, consequently, or as a result to wind up a line of reasoning, you probably should not need more than a few such connecting devices per page. Any more than that and it begins to look as though you were worried that the prose did not hang together on its own.

In short:

1. Begin sentences with short simple words and phrases communicating information that appeared in previous sentences, or with knowledge that you can assume you and your reader share.
2. Through a series of sentences that you want your readers to understand as a coherent, focused passage, keep your topics short and reasonably consistent.