段落( paragraph )是由表達(dá)單一中心思想(controlling idea or central idea )的一組句子(包括主題句 topic sentence,推展句supporting sentences及結(jié)論句concluding sentence)構(gòu)成，是文章結(jié)構(gòu)的基本獨(dú)立單位。本講我們將就主題句和中心思想這兩個(gè)方面展開(kāi)討論。

　　怎樣寫(xiě)好英語(yǔ)段落

　　段落是文章的縮影。寫(xiě)好了段落，就能比較成功地寫(xiě)出較好的文章。經(jīng)過(guò)中學(xué)英語(yǔ)基礎(chǔ)階段的學(xué)習(xí)之后，大學(xué)英語(yǔ)的寫(xiě)作重點(diǎn)就從選詞造句轉(zhuǎn)移到了聯(lián)句成段和聯(lián)段成篇上。進(jìn)行段落層次上的寫(xiě)作訓(xùn)練，是寫(xiě)好英語(yǔ)文章的關(guān)鍵一環(huán)。下面介紹的是段落結(jié)構(gòu)。

　　主題句與推展句

　　1. 主題句

　　主題句(topic sentence)是表達(dá)段落主題的句子。它用以概括段落大意，要求全段其他文字都圍繞它展開(kāi)。請(qǐng)看下例：

　　My mother has passed along to me certain rules for getting along with others. Don't argue with parents; they will think you don't love them. Don't argue with children; they will think themselves victimized. Don't argue with spouses; they will think you are a tiresome mate. Don't argue with strangers; they will think you are not friendly. My mother's rules, in fact, can be summed up in two words: Don't argue.

　　主題句中提出的 "certain rules" 指的是什么?展開(kāi)句中通過(guò)四個(gè) "Don't argue --" 逐一加以交代。從結(jié)構(gòu)來(lái)看，這是一個(gè)比較典型的段落，它包括了主題句，推展句和結(jié)論句(即本段中的末句)。

　　1.1 主題句的位置

　　主題句通常放在段落的開(kāi)端，其特點(diǎn)是開(kāi)門(mén)見(jiàn)山地?cái)[出問(wèn)題，然后加以詳細(xì)說(shuō)明。其作用是使文章的結(jié)構(gòu)更清晰，更具說(shuō)服力，便于讀者迅速地把握主題和想象全段的內(nèi)容。主題句可以放在段中起到承上啟下的作用，或放在段尾起概括全段的作用。但初學(xué)者比較難于掌握，因而在四級(jí)考試中，考生應(yīng)盡量采用將主題句放在段落開(kāi)頭的寫(xiě)作手法。

　　例1: Our life today depends very much on energy. In towns and in villages, on farms and in factories, machines have made life easier than it used to be. The machines use energy, and energy is needed for heating, lighting, communications, carrying goods -- everything. Factories and industrial plants use a great deal of energy to make the things that we use and buy and sell.

　　這段文字所講的主要是能源問(wèn)題。第一句就概括性地提出“我們目前的生活很大程度上依賴于能源”。而隨后出現(xiàn)的三句都是具體事例，對(duì)第一句進(jìn)行說(shuō)明和論述。我們可以斷定第一句為該段的主題句(斜體部分)。

　　例2: (主題句)No one can avoid being influenced by advertisements. (推展句1)Much as we may pride ourselves on our good taste, we are no longer free to choose the things we want, for advertising exerts a subtle influence on us. (推展句2)In their efforts to persuade us to buy this or that product, advertisers have made a close study of human nature and have classified all our little weakness.

　　以上這段由三句話組成。第一句是主題句，直截了當(dāng)指出無(wú)人不受廣告影響這個(gè)主題，接著列舉兩個(gè)推展句對(duì)其補(bǔ)充和支持，指出我們已無(wú)法自由選擇所需的商品，理由是廣告商已仔細(xì)研究了我們的心理，并完全掌握了我們的弱點(diǎn)。句子銜接自然，步步緊扣主題。

　　1.2 如何寫(xiě)好主題句中的關(guān)鍵詞

　　段落的主題句對(duì)主題的限定主要是通過(guò)句中的關(guān)鍵詞來(lái)表現(xiàn)的。關(guān)鍵詞要盡量寫(xiě)得具體些。對(duì)“具體”的要求包括兩個(gè)方面：一是要具體到能控制和限制段落的發(fā)展;二是要具體到能說(shuō)明段落發(fā)展的方法。準(zhǔn)確地把握關(guān)鍵詞是清楚地表達(dá)段落主題、寫(xiě)好段落主題句的重要前提之一。在上面的例1，例2中，主題句的關(guān)鍵詞分別為：depends very much on energy; no one can avoid being influenced. 我們?cè)倏聪铝欣洌?/p>

　　原句1: He can fix a bicycle himself.

　　斜體部分應(yīng)為主題句中的關(guān)鍵詞。但它只是限制了段落發(fā)展的部分內(nèi)容，并沒(méi)有告訴讀者該用哪種方法展開(kāi)，是用因果關(guān)系法還是用分類法?

　　修正：He can fix a bicycle himself in several simple steps.

　　修正：There are several reasons why he can fix a bicycle himself.

　　原句2: She tries to improve her looks.

　　斜體部分應(yīng)為主題句中的關(guān)鍵詞。她試著改變她面容的理由是什么?或者她采取什么方法來(lái)改善呢?我們無(wú)法從關(guān)鍵詞中清楚得知。

　　修正：She tries many ways to improve her looks.

　　修正：There are some reasons why she tries to improve her looks。

　　1.3 如何寫(xiě)好主題句的中心思想

　　主題句由兩部分組成，即主題(topic)和中心思想(controlling idea)。中心思想的作用是導(dǎo)向(control)和制約(limit)。我們前面談到的關(guān)鍵詞就反映了中心思想。所謂導(dǎo)向就是規(guī)定段落的發(fā)展脈絡(luò)，所謂制約就是限制主題的覆蓋范圍，兩者不可分割。沒(méi)有導(dǎo)向，內(nèi)容就會(huì)離題或偏題;沒(méi)有制約，內(nèi)容就可能超出一個(gè)段落所能容納的范圍。

　　對(duì)于初學(xué)寫(xiě)作的人來(lái)說(shuō)，“導(dǎo)向”的重要性容易理解，但如果由他們自己來(lái)構(gòu)思一個(gè)主題句，就可能忽視“制約”這一面。例如：

　　There are two ways in which one can own a book. The first is the property right you establish by paying for it, just as you have made it a part of yourself and the best way to make yourself a part of it is by writing in it.

　　本段的主題句如果沒(méi)有in which 引出的定語(yǔ)從句，那么two ways 不僅不能起制約作用，而且也不能起導(dǎo)向作用，句子本身讀起來(lái)也就使人覺(jué)得欠缺點(diǎn)什么。

　　Exercise is beneficial to your heart. A 22-year study was conducted by doctors in California. They found that people who work at physical jobs experience fewer heart attacks than other people. These active people work all the time at moderate speeds, their daily routine gives them an adequate amount of exercise and helps them stay in shape.

　　"Exercise is beneficial"這是毫無(wú)疑義的。但主題句中如不加上"to your heart"來(lái)加以 control 和 limit，那就流于空泛。

　　因此，緊緊把握主題句中controlling idea的導(dǎo)向和制約作用，是短文寫(xiě)作成功關(guān)鍵之一。

　　2.推展句

　　2.1 主要推展句

　　主要推展句(major supporting statement)的主要特點(diǎn)是：圍繞段落主題句展開(kāi)的每一個(gè)推展句本身都不要求作進(jìn)一步的說(shuō)明或證明，句與句之間的關(guān)系是相互獨(dú)立又是互相連接的。

　　例1：(主題句) There are several factors affecting climate. (推展句1)One factor is the mount of sunlight received. (推展句2)Altitude, or the height above sea level, also determines climate. (推展句3)The oceans have an effect on the climate of adjacent land. (推展句4)In addition, climate is influenced by the general circulation of the atmosphere.

　　主題句指出影響氣候的幾個(gè)因素。然后用四個(gè)擴(kuò)展句說(shuō)明四種因素。第一種是太陽(yáng)光的接收量，第二種是海拔高度，第三句和第四句分別是海洋和大氣環(huán)流因素。

　　2.2 次要推展句

　　次要推展句(minor supporting statement)是指對(duì)主要推展句作進(jìn)一步的事實(shí)分析和舉例說(shuō)明。它從屬于某一個(gè)或某幾個(gè)推展句。

　　例2：(主題句)I don't teach because teaching is easy for me. (主要推展句1)Teaching is the most difficult of the various ways I have attempted to earn my living: mechanic, carpenter, writer. (主要推展句2)For me, teaching is a red-eye, sweaty-palm, sinking-stomach profession. (次要推展句1)Red-eye, because I never feel ready to teach no matter how late I stay up preparing. (次要推展句2)Sweaty-palm, because I'm always nervous before I enter the classroom, sure that I will be found out for the fool that I am. (次要推展句3)Sinking-stomach, because I leave the classroom an hour later convinced that I was even more boring than usual.

　　從屬于主要推展句2的三個(gè)次要推展句起著解釋說(shuō)明作用，分別解釋red-eye, sweaty-palm, sinking-stomach的含義，這就更加形象生動(dòng)地證明了 "teaching is not easy" 這個(gè)主題。

　　2.3 主要推展句與次要推展句的關(guān)系

　　主要推展句與次要推展句的關(guān)系(relation)基本可以遵循下面的“三部分”(three-part)規(guī)則。

　　1〕每個(gè)主要推展句都應(yīng)該是對(duì)主題句中表示主要思想的關(guān)鍵詞的直接、明確的說(shuō)明。

　　2〕每個(gè)次要推展句都應(yīng)該說(shuō)明它的主要推展句。

　　3〕含有討論說(shuō)明或分析的問(wèn)題通常既要有主要推展素材，又要有次要推展素材。