規則：每個段落以一句主題句 (topic sentence)開頭，結尾須與開頭呼應。
本原則的目的同樣是幫助讀者閱讀，這種寫作方式能讓讀者在開始閱讀每個段落時，就掌握該段落的目的，且直到段落結束時都銘記在心。因此，在闡釋或議論時最常使用的段落結構為：
(a) 主題句在首句或前幾句出現；
(b) 接下來的句子解釋、建立或發展主題句的敘述；
(c) 末句強調主題句的想法，或陳述一些重要結論。
請避免以離題的敘述，或無關緊要的細節作為段落的結尾。
若文章的篇幅較長，寫作時可能必須說明某個段落與前述內容的關聯，或該段落在通篇文章中的功能。有時只須在主題句中加入一個詞語，如 again（同樣地）、therefore（因此）、for the same reason（由於同樣的原因），有時則須在主題句前加上一或數句有引導或連接功能的句子。若需要多個句子才能與主題句順利銜接，則建議將這幾個句子獨立為一個段落。
如上所述，同學在寫作時可以運用數種方式連結段落中的本文與主題句。你／妳也可以用不同的句式重述主題句、定義句中的詞彙、反駁與主題句相反的事實、提供通例或特例、說明句子的隱含意義或其可能導致的結果，來讓主題句要表達的意義更加明確。在寫作較長的段落時，同學可能會用到以上數種方法。
範例1 蘇格蘭小說家史蒂文森的經典散文〈徒步旅行〉
❶主題句。
Now, to be properly enjoyed, a walking tour should be gone upon alone.
若要好好享受徒步旅行，你應該自己一個人去。
❷否定相反的做法以闡明主旨。
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.
如果是一群人去，或就算只有兩個人，也只會是趟有名無實的徒步旅行；比起徒步旅行，這更像是去野餐。
❸以簡短的方式重述主題句，並提出三個原因支持；其中，第三個原因（「你必須擁有自己的步調」）是用反駁與主題句相反的事實的方式，來闡明意見。
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.
徒步旅行應該自己一個人去，因為自由是其中的精髓；因為如此一來，你便能隨時走走停停，或隨興改變路徑；因為你必須擁有自己的步調，而不是在一位快走冠軍旁小跑步，或因為一位女孩而停駐許久。
❹用兩種方式敘述第四個原因。
And you must be open to all impressions and let your thoughts take colour from what you see.
你也應該敞開心胸接受任何映入眼簾的印象，並讓所見之物為你的想法增色。
❺用另一種方式敘述同一個原因。
You should be as a pipe for any wind to play upon.
你該像把笛子，不管什麼風吹來，都能奏出美妙樂音。
❻引述英國散文家Hazlitt 的話說明同一個原因。
“I cannot see the wit,” says Hazlitt, “of walking and talking at the same time. 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.
海茲利特說道：「我看不出邊散步邊講話的好處。當我走在鄉間時，我只想像植物般悠然生長。」這段話說得實在中肯。
❼將Hazlitt 的話換句話說。
There should be no cackle of voices at your elbow,
to jar on the meditative silence of the morning.
你身邊不該有呶呶不休的人聲，破壞早晨冥想般的寧靜。
❽以豐富、生動的用詞再次重述第四個原因，形成強而有力的結論。
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.
而且當一個人用理性思考時，他便無法美好地沉醉在自然之中，這種沉醉來自空氣中的律動，源於大腦的微醺與慵懶，並在一種難以名狀的平靜之中落幕。
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英文原文：
RULE9
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.
Example 1 Robert Louis Stevenson, Walking Tour
❶ Topic sentence.
Now, to be properly enjoyed, a walking tour should be gone upon alone.
❷ The meaning made clearer by denial of the contrary.
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.
❸ 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.
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.
❹ A fourth reason, stated in two forms.
And you must be open to all impressions and let your thoughts take colour from what you see.
❺ The same reason, stated in still another form.
You should be as a pipe for any wind to play upon.
❻ The same reason as stated by Hazlitt.
“I cannot see the wit,” says Hazlitt, “of walking and talking at the same time. 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.
❼ Repetition, in paraphrase, of the quotation from Hazlitt.
There should be no cackle of voices at your elbow, to jar on the meditative silence of the morning.
❽ Final statement of the fourth reason, in language amplified and heightened to form a strong conclusion.
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.
─ ─摘自:《英文寫作聖經《The Elements of Style》》野人出版提供@
責任編輯：黎薇
