TIP 4 Use strong topic sentences that match the contents of the paragraph.

A topic sentence expresses a paragraph’s main idea. It usually comes at the beginning of a paragraph.

Well, that statement is inaccurate: topic sentences often get omitted from paragraphs, either by accident or to avoid sounding repetitive.

Think of each topic sentence as a jurisdictional statement for that paragraph. It tells you what the rest of the paragraph will discuss. If the rest of the paragraph strays, you need to revise either your topic sentence or the rest of the paragraph.

Perfect topics sentences make it possible to read only the first sentence of each paragraph and still follow the argument. The first sentence of each paragraph implicitly says, “I will prove the claim that I make in the topic sentence.” The rest of the paragraph does so — except that the last sentence might remind the reader what the paragraph just proved. So is it really possible to follow an entire argument merely from the topic sentences? Sure. Appendix B contains a sample passage that contains spectacular topic sentences. As you will see, those sentences allow readers to follow the author’s argument simply by reading the first sentence of each paragraph.

You don’t need, however, to be that obsessive about topic sentences. As with any other writing tip, your prose will become rote if you follow this suggestion too vigilantly. In your Statement of Facts, you may omit topic sentences lest they sound like unsubstantiated rhetoric. Even so, each paragraph in a Statement of Facts should have some logical break from the paragraphs that precede or follow it. In your Argument, however, most paragraphs should have a topic sentence that foretells what you’re about to prove.