2.段落尾句是主题句的规律

(1)阐述一个不常见的或难以令人接受的观点的段落。

(2)旨在说服读者相信甚至信服其论点的段落。

尾句是主题句的段落总是用归纳法撰写的，其程序是先表述细节或交代论据，最后作出概括性的结论，以总结性的句子收尾。这种写作方法的特点是从个别到一般，由特殊性到共性。请看下例：

If you hadn't known them, you would have thought Joe and Jim were quite alike. They were both tall and wore long and fair hair. They both walked with a steady stride (坚定的步伐). They both spoke in a deep voice that made them selves seem much older than they really were. Both of them wore dark clothes as a rule, and they liked light coloured ties. But that was all the likeness they had. In other things they were sharply different. Joe was considerate and helpful, and everyone liked him. Jim, however, was very selfish and often flared into terrible anger (勃然大怒) at little things that displeased him. Alike as Joe and Jim were on the surface, they were really very different in nature.

这段文字从乔与吉姆两个人相像和不同的细节叙述，最后一句作了归纳总结：这两人表面相似，但实质极不相同。

3.段落中间句是主题句的规律

表述某种观点的段落的主题句往往处于段落的中间。这样段落先以一句或几句为主题句的出现作铺垫，或是交代一个细节或论据。在主题句出场后，仍有适当数量的句子陈述细节或继续给予例证。这类段落包括几个层次：引题—主题思想—解释或“提问”—回答问题或继续给予例证。这样段落的撰写总是遵循这条规律：先归纳后演绎。给出一两个例证之后，作出概括性的总结，然后根据这一结论再给予例证来证实其论点。请看下例：

When you throw a ball up into the air as fast as you can, the ball reaches a point where it seems to pause for a moment, and then it comes down. When a bullet (子弹) is shot straight up, it will travel much faster and higher than a ball, but it, too, will come down. Whatever goes up must come down. We have al-ways thought this to be true. An airplane may climb to a height of seventeen miles and then travel far and long. Yet it does not stay up forever. Finally, like every-thing else, the plane must come down.

本段文字中间划线的这句话是主题句。其行文顺序与写作方法与上述的发展程序完全吻合。