怎樣展開一個段落？

我們知道，文章由段落組成，段落的發展從主題句開始，段落由展開句組成。所謂的展開句就是在文章段落中闡明主題句的一些句子。

很多人在寫英語作文時會遇到這樣的問題：不知道怎樣寫展開句。他們在拿到作文題目後能夠很快確定文章的基本結構和主題句，但對主題句（論點）進行論證時卻發現寫了兩三句後就無話可說，導致分析論證流於表面，無法深入。

遇到這種問題時，可以採取下面這幾種方法進行擴展：

1.舉例法：

舉例法是目前議論文寫作中最常見，同時也是應用最廣泛的一種段落展開方法。通過舉例能夠讓文章內容更加豐富，同時更加具有說服力。

比如，有這樣一個作文題目：Governments should not fund any scientific research whose consequences are unclear.

如果你支持題目的觀點，可以提出這樣的分論點：Being circumspect about research whose objectives are too vague can help us avoid significant opportunity costs. 展開該分論點的一個方法是舉例，比如可以列舉美國的「星球大戰」研究計劃的例子：

Being circumspect about research whose objectives are too vague can help us avoid significant opportunity costs. Consider the "Star War" defense initiative championed by the then US President Ronald Reagan during the 1980s. In retrospect, this initiative was ill-conceived and largely a waste of taxpayers money —— money that could have been devoted to addressing pressing socio-economic problems of the day, such as AIDS, environmental damage, poverty and drug trafficking. As it turned out, at the end of the "Star War" debacle America was drawn into a quagmire of economic recession and social unrest, to the detriment of the nation at large.

使用舉例法需要寫作者具有一定的素材積累。平時閱讀的時候我們要留意收集一些具有一定通用性（即能用於很多題目的論證）同時又有一定的獨特性（即沒有被用得很濫）的例子。

2.反證法

反證法的思路是「如果不（接受本段的論證點），會（產生什麼樣的結果）」，通過這樣的方式來對問題進行更加深入的思考。舉個例子，對於這樣的題目：Students should always question what they are taught instead of accepting it passively. 我們可以提出這樣的分論點：Students in fields such as law and political science should think critically about current legal systems. 學習法律和政治學的學生應該學會質疑當今存在的各種法律法規的正確性。通過反證法可以進行思路擴展：如果他們不這樣做的話，會發生什麼，從而提升論證的深度：

Students in fields such as law and political science should think critically about current legal systems. While law students must learn to appreciate timeless legal doctrines and principles, they should continually question the fairness and justification of current laws. Without such skepticism, our laws would not evolve to reflect changing societal values and to address new legal issues brought by new technologies, for example AI and self-driving cars.

3.分類法

分類法也是段落展開的常見方法。分類法根據事物的特點分別歸類，很多東西可以被分成不同的類別，不同的東西也可以被歸為同一類。主題句確定後，段落的內容有時可以用分類順序來組織和發展。比如，同樣對於上面的題目：Students should always question what they are taught instead of accepting it passively. 我們可以採用分類法進行展開，即對於不同專業領域的學生（比如物理專業，藝術專業，法律專業），質疑精神對他們來說都同樣重要：

The value of skepticism can be illustrated by examples from various fields of study. For students in the field of physics sciences, the ability to question what they are taught is essential. History has seen many physics students, for example Copernicus and Galileo, who queried what they had been taught, thereby paving the way for innovations, invention and discoveries. For art students, it is often bold challenge to established styles and forms, rather than subpar mimicry, that enables them to produce genuinely new art. Even in fields such as law and political science, students must think critically about current legal systems; otherwise, exploitation, tyranny, and prejudice go unchecked.

4.因果法

因果法是論述類文章中最常使用的方法，因果法用於說明事物發展的原因和結果，可根據結果分析原因，也可以由原因推導結果。因果法非常適合用來擴展思路。如果你文章寫到一半覺得無話可說，記得多想想「原因和結果」：是什麼原因導致了現在正在描述的現象？現在描述的現象又會導致什麼樣的結果？把這兩點想清楚，文章思路就有了。比如上一篇推送裡面我們分析的一篇文章：People believe that using mobile phones and computers to communicate makes us lose the ability to communicate with each other face to face. To what extent do you agree or disagree?

如果我們持同意態度的話，會得出這樣的主論點：Using mobile phones and computers to communicate makes us lose the ability to communicate with each other face to face.

確定了論點之後，我們可以用「因果法」來展開：為什麼使用手機和電腦會降低人們的面對面溝通能力？造成人們面對面溝通能力下降的因素有哪些？這些因素會導致什麼樣的結果？

仔細分析之後不難得出下面兩條結論：

1）很多人在使用電腦或手機聊天的時候很難保持專註，因為他們會受到大量的信息干擾（比如手機推送的新聞和遊戲信息等）。習慣了網路聊天的人注意力持續時間會變短，談話的時候容易分心，這會對他們在現實生活中的交流造成障礙。

2）不少人習慣了在網路聊天中使用各種流行語和縮寫，但這些網路流行語往往難登大雅之堂。如果這種習慣被帶到現實生活中來，就會給人造成不好的印象。

因此可以這樣展開：

Smart phones and computers could in many ways hinder our face-to-face communication skills. Take conversational behaviour. Heavy users of such electronics often have a short attention span and are more likely to jump from topic to topic when an idea springs to mind. As a consequence, they may become unfocused and sidetracked during offline conversations. Internet slang also does its bit. Today, youngsters who text with abbreviated forms of words tend to speak with the same acronyms and use internet catchphrases heavily. These forms of talking are often construed as flighty and uneducated, from which misunderstandings ensue.

在實際寫作中很少將一種方法運用到底，一般都是將上面多種方法結合，例如反證+舉例，因果+舉例，分類+反證等，這樣論證效果會更好。

同時，為了使展開句寫得順暢連貫，我們還要留意連接詞的使用，例如：

轉折關係：while, yet, but, however

並列關係：and, also, likewise

讓步關係：though, although, despite, in spite of

遞進關係：moreover, what is more, furthermore, in addition, besides

寫作是思考的反映，經歷什麼樣的思考就會寫出什麼樣的文章。因此，要真正寫好一個段落一篇文章，除了採取以上幾種方法之外，還要學會訓練自己的思考能力，對日常發生的大小事件、別人的觀點，要多從不同層面思考它們的前因後果、成立的前提、適用的領域等，讓寫作水平和思維能力同步提升。