上一讲我们谈到了文章的主题，这一讲我们就开始研究文章的主题思想。首先明确一下概念，概括篇章（或段落）的思想就叫做主题思想。先看一下可能的问话形式：
II. CENTRAL IDEA
1. What is the main idea of the paragraph?
2. The main idea (central thought / idea of the paragraph is ______.
3. Which of the following sentences best expresses the main ides?
4. The main point of the paragraph is ______.
5. The paragraph centers on the point that ______.
6. Which of the following best states the theme of the paragraph?
主题思想在一篇文章中的表达可能有两种方式---隐含式表达和直白式表达。隐含式表达是指在整个段落中没有总括性的句子，全是陈述句或是情节句，主题思想是以一种隐含的方式表达出来的。直白式表达则恰恰相反，文章中有主题句。要注意的事，主题句的位置可能是在篇首，篇中或者是篇末，有时甚至有几个主题句。请看一下这篇文章，辨别主题思想，并且区分式隐含式表达，还是直白式表达。
IIA.
During the American War of independence, women were involved in the active fighting in three ways. First, as members of a distinct branch of the Continental Army, referred to as "women of the Army," women staffed field hospitals and acted as military support in such roles as water carriers. In an emergency, women water carriers, who had plenty of opportunity to observe the firing of cannons, could replace a wounded comrade. The second way that women were involved in active fighting was as regular troop members who wore men's uniforms and fought side by side with their male counterparts. Theoretically, women were not supposed to be recruited into the Continental Army, but if a woman was a good soldier, no one made an issue of sex at a time when the army was so short of soldiers that boys not yet in their teens were also being recruited in violation of rules. Third, women were occasional fighters affiliated with local militia companies of committees of safety formed to protect the local community.
What is the main idea expressed in the passage?
A. Women played an important role in military hospitals during the Revolutionary war.
B. The Continental Army was successful in teaching women to fire cannons.
C. The services of women on committees of safety were crucial in winning the war.
D. Women were active in combat during the Revolutionary War.
这篇文章结构很清晰，第一句话是主体句，后面三句话从三个角度来进一步说明。所以，正确答案是D，又因为第一句话是总括性的句子，所以这是一种直白式表达。解答这类问题时，有以下四个技巧可以考虑：
1． 不为无关的细节说纠缠。
2． 仔细读每一段的开头，特别是最长的段落。
3． 如果文章只有一段，文章的开头两句极为重要。
4． 阅读时，可以在你认为重要的句子，细节下画线。
请再看一篇短文
IIB.
Joshua Bingham studied four years at the University of Paris and decided to leave before his graduation. He transferred to the University of Berlin and graduated with honors. Harvard Law School and, later, Boston College
provided him with an excellent legal background. He is presently a corporation lawyer in Miami, Florida.
这篇文章很显然，所有的句子都是描述性的句子，所以就需要学生自己总结出主题思想来。综合考虑后，我们可以写出如下的主题思想：
Joshua Bingham received an excellent education。
下面这个练习供你们独立完成，答案是 C。
IIC.
Pollution spoils our environment in many ways. The air we breathe, for instance, is constantly polluted by smoke and by chemicals such as carbon monoxide in the exhaust fumes of car and other kinds of motor vehicles.
For wild life, however, there are even greater dangers in the pollution of water - of rivers, for example, or lakes and seas. A good illustration of this is the oil released from tankers at sea. It kills all kinds of sea animals, including birds, whose feathers become covered with oil so they cannot fly, as well as fish and other forms of marine life, other causes of water pollution include power station, which release warm water into rivers. This kills the fish and plants which live there. These are only a few examples; there are many more.
What is the central idea of the passage?
A. It tells how many kinds of chemicals can be found in air and in the sea.
B. It tells how the air we breathe is polluted.
C. It tells in what ways the world becomes dirty and unsafe for living things.
D. It tells how rivers, lakes and seas are polluted.
