The Elements of Style · Rule 9

As a rule, begin each paragraph with a topic sentence, end it in conformity with the beginning.

Again, the object is to aid the reader. The practice here recommended enables him to discover the purpose of each paragraph as he begins to read it, and to retain this purpose in mind as he ends it. For this reason, the most generally useful kind of paragraph, particularly in exposition and argument, is that in which

(a) the topic sentence comes at or near the beginning;

(b) the succeeding sentences explain or establish or develop the statement made in the topic sentence; and

(c) the final sentence either emphasizes the thought of the topic sentence or states some important consequence.

Ending with a digression, or with an unimportant detail, is particularly to be avoided.

If the paragraph forms part of a larger composition, its relation to what precedes, or its function as a part of the whole, may need to be expressed. This can sometimes be done by a mere word or phrase (again; therefore; for the same reason) in the topic sentence. Sometimes, however, it is expedient to precede the topic sentence by one or more sentences of introduction or transition. If more than one such sentence is required, it is generally better to set apart the transitional sentences as a separate paragraph.

According to the writer's purpose, he may, as indicated above, relate the body of the paragraph to the topic sentence in one or more of several different ways. He may make the meaning of the topic sentence clearer by restating it in other forms, by defining its terms, by denying the contrary, by giving illustrations or specific instances; he may establish it by proofs; or he may develop it by showing its implications and consequences. In a long paragraph, he may carry out several of these processes.

• 1 Now, to be properly enjoyed, a walking tour should be gone upon alone. 2 If you go in a company, or even in pairs, it is no longer a walking tour in anything but name; it is something else and more in the nature of a picnic. 3 A walking tour should be gone upon alone, because freedom is of the essence; because you should be able to stop and go on, and follow this way or that, as the freak takes you; and because you must have your own pace, and neither trot alongside a champion walker, nor mince in time with a girl. 4 And you must be open to all impressions and let your thoughts take colour from what you see. 5 You should be as a pipe for any wind to play upon. 6 "I cannot see the wit," says Hazlitt, "of walking and talking at the same time. 7 When I am in the country, I wish to vegetate like the country," which is the gist of all that can be said upon the matter. 8 There should be no cackle of voices at your elbow, to jar on the meditative silence of the morning. 9 And so long as a man is reasoning he cannot surrender himself to that fine intoxication that comes of much motion in the open air, that begins in a sort of dazzle and sluggishness of the brain, and ends in a peace that passes comprehension. - Stevenson, Walking Tours.
• 1 Topic sentence. 2 The meaning made clearer by denial of the contrary. 3 The topic sentence repeated, in abridged form, and supported by three reasons; the meaning of the third ("you must have your own pace") made clearer by denying the contrary. 4 A fourth reason, stated in two forms. 5 The same reason, stated in still another form. 6-7 The same reason as stated by Hazlitt. 8 Repetition, in paraphrase, of the quotation from Hazlitt. 9 Final statement of the fourth reason, in language amplified and heightened to form a strong conclusion.
• 1 It was chiefly in the eighteenth century that a very different conception of history grew up. 2 Historians then came to believe that their task was not so much to paint a picture as to solve a problem; to explain or illustrate the successive phases of national growth, prosperity, and adversity. 3 The history of morals, of industry, of intellect, and of art; the changes that take place in manners or beliefs; the dominant ideas that prevailed in successive periods; the rise, fall, and modification of political constitutions; in a word, all the conditions of national well-being became the subject of their works. 4 They sought rather to write a history of peoples than a history of kings. 5 They looked especially in history for the chain of causes and effects. 6 They undertook to study in the past the physiology of nations, and hoped by applying the experimental method on a large scale to deduce some lessons of real value about the conditions on which the welfare of society mainly depend. - Lecky, The Political Value of History.
• 1 Topic sentence. 2 The meaning of the topic sentence made clearer; the new conception of history defined. 3 The definition expanded. 4 The definition explained by contrast. 5 The definition supplemented: another element in the new conception of history. 6 Conclusion: an important consequence of the new conception of history.

In narration and description the paragraph sometimes begins with a concise, comprehensive statement serving to hold together the details that follow.

• The breeze served us admirably.
• The campaign opened with a series of reverses.
• The next ten or twelve pages were filled with a curious set of entries.

But this device, if too often used, would become a mannerism. More commonly the opening sentence simply indicates by its subject with what the paragraph is to be principally concerned.

• At length I thought I might return towards the stockade.
• He picked up the heavy lamp from the table and began to explore.
• Another flight of steps, and they emerged on the roof.

The brief paragraphs of animated narrative, however, are often without even this semblance of a topic sentence. The break between them serves the purpose of a rhetorical pause, throwing into prominence some detail of the action.