简单来说，论证是能够将观点和论据串联起来的东西。在托福独立写作中，因果和让步是需要大家一定要掌握，并且要在文章中正确使用的两个基本的论证逻辑。常见的论证方法有举例论证，对比论证，因果论证和类比法。
1. 举例论证
例证法不仅使文章具体生动还会使观点更有说服力。
Competition between friends usually causes damage to friendship. Do you agree or disagree?
Certain kinds of competition can indeed be destructive. The danger of competition among friends is particularly acute. I recall from my childhood two close friends, who came to school together and played basketball together. Once a fierce competition between two basketball teams led by both of the two friends tied at the last moment, and one contentious 3-point shot helped one team win but ended their friendship. They have never talked with each other, even meeting face to face.
2. 因果论证
恰当使用因果论证可以使逻辑有无可辩驳的力量，比如：
Does playing games or doing sports with their children deserve more time from parents or helping their children with their schoolwork?
For one thing, students need to do more sports or outdoor activities to maintain physical and mental health. Under heavy pressure caused by various exams, the students need to get released from the great tension. The reports about some children who couldn’t stand the failure of the exams or the criticisms from teachers and committed suicide are the tragedies which reflect the seriousness of the problems. Therefore, more and more parents have come to realize that spending time with their children to ensure their healthy and happy growth is much more important.
3. 对比分析
通过强烈对比突出问题的严重性，比如：
Unfortunately, offering to give a hand when someone is in need has gone out of style. It used to be a mark of class to give support despite your own financial straits. You didn’t have to empty your purse to help; the point was to show that you really cared and they were not isolated. But with today’s trust crisis, the frequent warning you hear is never to lend money to your friends.
再比如：
Ours has become a society of mortgage slaves. Ten years ago 8000 yuan per square scared many house buyers away. Today 80,000 yuan per square for the house inside the fifth ring road is considered a boon dropping from the sky. And while five years ago, waiting for the house price to decline was still the hope of some wealthy potential buyers, the potential buyer today is increasingly baffled and completely knocked down without seeing a silver line.
4. 类比法
类比就是打比方，例举一个生活中读者都熟悉的、与你要说明的观点具有相同性质的事例，往往能使读者更容易理解你的观点。
比如：
Full ownership of (a book) comes only when you have made it a part of yourself, and the best way to make it a part of yourself is by writing in it. An illustration may make the point clear. You buy a beefsteak and transfer it from the butcher’s refrigerator to your own. But you do not own the beefsteak in the most important sense until you consume it and get it into your bloodstream. I am arguing that books, too, must be absorbed in your bloodstream to do you any good.
