Topic sentences and how to use them

During your studies, you will be probably be told at least once that you should pay attention to topic sentences. These sentences come at the beginnings of paragraphs and introduce the central ideas that are about to be developed. “Use topic sentences,” the advice-givers say, “and your writing will become clear”.

And yet many examples of fine writing do not use topic sentences. I’ve read many paragraphs where the first sentence does not point towards the incoming payload at all, and yet the authors of these paragraphs are praised for their style and clarity. Then why should we use them? Are topic sentences another example of a fictional device made up to turn writing into a paint-by-numbers exercise?

The first thing we should note is that academic writing is not just a stuffier version of regular writing; instead, what sets it apart is that it has a narrower purpose. It does not seek to entertain or mystify (we hope), but to communicate ideas. Most of these ideas are difficult to grasp, and so it is the academic writer’s duty to present them in as clear a way as possible.

A good way to ensure that the reader stays focused on the argument is to constantly set up questions in the reader’s mind and then answer them. And this is what topic sentences let you do, because they are not mere statements of fact but miniature claims that the reader should want to have elaborated.

Let’s take a look at an example from the article Waiting for Universal Grammar (in press). The author, Geoff Pullum, has just quoted from a paper claiming that children can learn to say things from experience, but cannot learn not to say things that are grammatically disallowed. Pullum’s next paragraph begins like this: “It cannot be true that you can never learn from experience that something is disallowed”. When the reader encounters this sentence, a few questions will naturally arise. Why can’t it be true? Do you have a counterexample? Is there an explanation for how this learning might occur? Some of these questions will be answered immediately, and this is how Pullum keeps the momentum going. He immediately gives a counterexample, satisfying the reader’s curiosity. But he waits to answer the question of how this learning occurs until later on in the essay, when he treats Bayesian abduction.

This is a powerful way of improving the unity of the essay. The reader is promised a reward for continuing to read the paragraph. At least part of that reward is handed out immediately, and sometimes another part is reserved for later, once other essential parts of the argument have been put into place.

So when you are working on topic sentences, don’t think of them as just one-sentence summaries, but as promises to the reader, raised questions that will have to be answered. Use them to lure, to provoke. How are you going to convince the reader to keep on going through paragraph after paragraph, section after section? Topic sentences aren’t the only way of accomplishing this, but they are an important tool in the writer’s belt. Academic prose can be enjoyable if the reader never has to wonder what the point of it all is.