上篇给大家讲了举例论证这一重要的论证方法，此篇介绍另一个很重要的论证方法

对比论证往往是对两个事物进行对比分析，或者将一个事物的正反面进行对比分析。对比论证的目的是用反面来突出正面。比如以下这一段：

Students who go to university immediately after graduation can better adjust themselves to the academic life, whereas/while those who take a gap year off are very unlikely to refocus their attention on study.

在这一段话中，作者是想突出“毕业后就立刻上大学”（正面）是比较好的做法，在说完这种做法的好处之后，又讲下“毕业后休学一年再去上大学”（反面）是不好的，以此来突出“立刻上大学”的优势，这就是对比论证。

Cities are more densely populated and there are more job opportunities available, so they earn more money. This means that they can improve living standards and afford more consumer goods than ever before. By contrast, employment opportunities are scarce in rural areas, due to the fact that many industries are underdeveloped and many inhabitants’ buying power is limited.

这段话运用对比论证突出城市相比于农村的优势。

在使用对比论证时，正反面的表达要尽量避免重复性。比如正面说了adjust to，那么反面论述时不要说cannot adjust to, 可以换一些表达。如果觉得比较有难度，也可以用compared with这个结构，这样就可以直接写出正面的内容，不需要两边转换正反都详细分析。例如：

Compared with rural areas, cities are more densely populated and there are more job opportunities available, so they earn more money. This means that they can improve living standards and afford more consumer goods than ever before.

对比论证常用逻辑连接词

A…, while/whereas B…

A…, By/In contrast, B…