Writer's WebReasoning: Methods of Argument & Avoiding Fallacies
By David Roberts

When arguing, sometimes one person says to the other, “Well, that’s just your opinion. Maybe it’s right for you.” These statements might sometimes be true, but they are used all too often to avoid an honest evaluation of ideas. Some opinions, after all, are supported more than others. These reminders should help you to make your arguments well-supported and avoid fallacies in your own writing. As an added benefit, this will likely help you to detect poorly-supported points in others' writing:

Ways to support an argument

1. Analogy

Making an argument through analogy involves comparing two objects (events, situations, people, and the like) and arguing that, because they are similar in some way, a similar action should occur in both situations. For instance, someone might say:

“We should keep our books from last semester; giving them back to the bookstore is just like giving them away anyway, and we shouldn’t just give our books away.”

The person making this claim begins with the premise that one situation – giving books away – is wrong, and argues that a second situation – returning them to the bookstore – is analogous to the first situation. These premises are used to justify taking a similar action in both cases.

Analogies are important to one’s argument, but it is all too easy to apply one situation improperly to another. One must determine the similarity between two situations and, once this similarity is found, one must ask if this similarity is the important and relevant similarity. That is, does this similarity between two situations justify taking the same action in both? See our page on Other Logical Fallacies for more about faulty analogies.

2. Example/Detail

In some cases analogies will be less applicable than in others. Instead of using analogies, writers may find it useful to use examples and details to illustrate some of their assertions. For example, John might say:

“This class is really hard. I spent two hours a night studying for the past week and I still got a C on the last test!”

In this case, John uses a single event – an example or detail – to make a broader claim about the difficulty of a class. Of course, for it to be an appropriate example, it must be representative. In John’s case, it would not be a good example if he cited one difficult test in an otherwise extremely easy class. See our section on Supporting Arguments with Detail for more assistance with this issue.

3. Proof by Absurdity or Contradiction

Proving your position to be correct can also occur by proving that the opposite viewpoint is either contradictory or ridiculous. This is accomplished by assuming that one’s opponents are correct and then reasoning from that to conclude that this assumption leads to something impossible or absurd. Because it leads to an impossible or absurd result, this assumption should be rejected. For example, imagine a lawyer in a courtroom defending a client. The lawyer might say:

“Assume my client, John, did commit this crime. But in order to commit this crime, we can all agree, he must have been at the scene of the crime when it took place. However, thirty people saw my client at a restaurant two hours away from the crime scene two minutes before it took place. For John to have committed this crime, he must have been two places at once. But this is surely impossible! It therefore follows that my client did not commit this crime.”

While proving an argument by contradiction is legitimate, one must be careful of a few things. First, one must be careful not to commit the False Dilemma fallacy. One cannot conclude that a pen is red simply on the basis that it is impossible or ridiculous for it to be green. It could also be blue. Hence, it is important to remember what one does and does not know: if it is impossible or ridiculous for it to be green, all one knows is that it is not green.

Second, one must be careful that the reason for rejecting an assumption is legitimate. Those who believed that the Earth was flat succumbed to this fallacy: “Assume that the Earth is round. This would mean everything we’ve believed for so long is incorrect and we'd have to change our beliefs! Therefore, the Earth must not be round!” One cannot simply decide that results should be rejected because they are an undesired outcome. In order to reject a premise, its conclusion must be impossible or absurd, not simply unwanted.

4. Sources of Authority

Writing for academic audiences requires more than simple personal opinion. As we saw earlier, not all opinions are created equal. One way to bolster an argument is to use the word of an expert. This may be particularly useful for research papers where an expert conducted empirical research and has unique findings.

Like the other ways to support your argument, however, one must be careful not to misuse or overuse this method of support. Academic writing is about more than personal opinion, but it is also about more than uncritical agreement; simply accepting a statement because an authority says it may not persuade your audience. If you decide to use sources to support your points, be certain to critically engage your sources and, when agreeing with them:

1. Base your agreement on more than their position alone, but also their argument.
2. Make sure to address other authorities’ challenges to this point of view.

See our section on Using Sources Effectively for more resources on this issue.

Avoiding Fallacies

Not reasoning poorly is just as important as reasoning well. A single fallacious argument in a paper may result in many points - or a letter grade or two - subtracted. As you go through the writing process, the following three pieces of advice will help you avoid these errors in reasoning.

1. Challenge yourself

Is this really true? I’m not sure, but you should ask yourself (and others)! As the author of the paper, you know the most about the argument you’re trying to make. What are its important points? What are its weak points? Are any of the important points also some of the weak points?

Pretend you are disagreeing with your argument each step of the way. Do your best to think of reasons why what you say may not be true. It may be easier to do this a few days after writing a draft in order to gain distance from the argument.

You should also keep in mind that sometimes, you will agree with the objection that you identify and the original argument will change. Therefore, it is best to go through this self-questioning throughout the writing process rather than as a brief afterthought when editing the night before a paper is due.

2. Learn from experience

Are there any particular fallacies you are prone to committing? One must know the argument one intends to make, but one must also know him- or herself. Do you often rely on the status of experts rather than the substance of what they say or their relevant knowledge about the topic? Or do you sometimes take the lack of proof against something to be evidence that it is true?

No matter what mistakes you have made in the past, you should keep them in mind in order to prevent them from happening in the future. You may find it helpful to look through graded papers from previous assignments in order to find out the errors you commonly make.

3. Outline your arguments

What evidence supports what claims which support what conclusion? After writing your paper, read your paper for function and structure, writing down on a separate sheet of paper the evidence, claims, and conclusion. In other words, ask "why?". Investigate the purpose of each sentence in your paper. See our page on Glossing Your Ideas for more practical advice about how to go through this process.

There are numerous benefits to going through this sometimes tedious and always methodical process. First, you will be able to identify unwarranted assertions, allowing you to either support them or modify them so that they are warranted (for example, less categorical or sweeping). There are other benefits as well: one will also likely prevent major digressions, shifts of scope, and will have a clearly-flowing and well-organized paper.


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