作者在导言部分提出论点之后，可以用归纳法、演绎法等证明这一论点。
1归纳法
归纳法是一种逻辑推理方法。一些论说文通过这种方法组织素材，从逻辑上论证某一观点的正确性，在具体写作中，作者首先要列举事实（这一点类似于说明文的列举法），然后根据这些事实自然地引申出一个符合逻辑的结论。例如：
Fact 1：Each member of family has a bad cough for weeks after they moved to the new house.
Fact 2：Some other people living in this building have also suffered from cough.
Fact 3：This building has been newly decorated.
Conclusion: The decoration material must contain some pollutants.
2演绎法
演绎法是与归纳法相对的另一种逻辑推理方式。论说文在使用演绎法组织文章时，作者首先要提出一个众所周知的原理或结论，然后据此及相应的事实再推论出作者的结论。
Wellknown concept: Polluting decoration material does harm to peoples health.
Fact 1：Each member of family has a bad cough for weeks after they moved to the new house.
Fact 2：Some other people living in this building have also suffered from cough.
Fact 3：The building has been newly decorated.
Conclusion: The decoration material must contain some pollutants.
三、论说文的种类
这里所说的论说文的种类是根据大学英语四级考试中命题作文的出题特点和写作方法、写作目的来划分的,目的是为了让考生能更好地抓住写作的重心，更快地掌握写作的技巧。四级英语考试的命题作文中经常出现的论说文类型有以下三种：分析性论说文、解释性论说文和批驳性论说文。
1.分析性论说文
分析性论说文的写作重点在于分析主题的性质，提出具体的建议或解决方案。作者可以依据论说文的结构（导言、正文和结尾）在第一段引入主题，随后在正文部分对主题进行分析，最后在结尾部分提出建议。例如Advantages of a Job Interview(1995年6月全国四级作文题),Getting to Know the World Outside the Campus (1997年6月全国四级作文题)都属于这一范畴。下面是一篇以污染为主题的作文：
Pollution is harmful to human beings. Polluted water causes many kinds of diseases such as diarrhea, vomit, etc. And sometimes these diseases even take mans life. Dirty air or airborne garbage causes stinging eyes and running nose.
Nowadays pollution problems have not been completely solved. Pesticides are widely used almost everywhere. They pollute soil, water and food. They have the power to make our streams fishless and our gardens and woodlands silent and beardless. Some factories are still using sea as a dumping place for wastes. Some lakes are still dirty. Quite a few chimneys are still pouring smoke into air and noise pollution remains serious.
Measures should be taken to control pollution. Legislative steps should be introduced and pollutants should be trapped before they are poured out of chimneys.
文章在导言部分引入主题：污染有害于人类。在正文部分分析了污染会给人类造成哪些具体的危害。最后在结尾部分提出了防治污染的措施。
2.批驳性论说文
批驳性论说文在各类试题中多是给出一些有争议的观点或做法，由考生对其进行分析、评论和驳斥，目的是为了得出正确的结论或者给出问题的解决方法。例如：Is Failure a Bad Thing？(1992年1月四级作文题)/Do “Lucky Numbers” Really Bring Good Luck？(1998年6月四级作文题)/Can Money Buy Happiness？(1996年1月四级作文题)/Reading Selectively or Extensively?(1996年6月四级作文题)
［例1］
Does Lottery Really Bring Us Luck?
Nowadays, many people are enthusiastic about buying all kinds of lottery tickets. The purpose of them is to realize their dreams of becoming rich. However, some people dont agree on this activity. They think trying luck on lottery is harmful. They believe that such practice is likely to make people expect good luck rather than hard work to achieve their goals.
I believe that it is a meaningful thing. It does more good than harm to our society. First, the money collected can be used to help poor and the needed. Second, the accumulated money will be helpful to promote our welfare and make contribution to the whole society. Moreover if you are lucky enough, you may be rewarded.
So I favor lottery tickets, if I have some money, Ill buy them.
作者在第一段提出了人们对彩票的两种不同观点，接下来在正文部分提出自己的观点，并阐述了自己之所以坚持这一观点的原因。
［例２］
Can Success Be Measured in Terms of Money?
In the mind of some people money is the only yardstick of success. They bellies that if people have money, they may earn their position, fame, and popularity in the society. Consequently they can live a comfortable life.
However, others dont agree with them, they think that success cant be measured in terms of money. For example, Lei Feng and Liu Hulan had almost no personal property when they died, but they have gone down in history because their lives were dedicated to the Party and the people.
In my opinion, measuring success by money alone is rather misleading. It will mislead people to strive to make money, sometimes even by unfair means. Eventually this will do harm to our society.
作者在文章中首先摆出两种不同的观点：有人认为金钱是衡量成功的惟一标准，而有人却不同意这一观点，接下来作者用了雷锋和刘胡兰两人的事例来论证成功与否并不能靠金钱来衡量。最后作者发表了自己的观点。
