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Purdue Online Writing Lab Purdue OWL® College of Liberal Arts

Developing Strong Thesis Statements

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These OWL resources will help you develop and refine the arguments in your writing.

The thesis statement or main claim must be debatable

An argumentative or persuasive piece of writing must begin with a debatable thesis or claim. In other words, the thesis must be something that people could reasonably have differing opinions on. If your thesis is something that is generally agreed upon or accepted as fact then there is no reason to try to persuade people.

Example of a non-debatable thesis statement:

This thesis statement is not debatable. First, the word pollution implies that something is bad or negative in some way. Furthermore, all studies agree that pollution is a problem; they simply disagree on the impact it will have or the scope of the problem. No one could reasonably argue that pollution is unambiguously good.

Example of a debatable thesis statement:

This is an example of a debatable thesis because reasonable people could disagree with it. Some people might think that this is how we should spend the nation's money. Others might feel that we should be spending more money on education. Still others could argue that corporations, not the government, should be paying to limit pollution.

Another example of a debatable thesis statement:

In this example there is also room for disagreement between rational individuals. Some citizens might think focusing on recycling programs rather than private automobiles is the most effective strategy.

The thesis needs to be narrow

Although the scope of your paper might seem overwhelming at the start, generally the narrower the thesis the more effective your argument will be. Your thesis or claim must be supported by evidence. The broader your claim is, the more evidence you will need to convince readers that your position is right.

Example of a thesis that is too broad:

There are several reasons this statement is too broad to argue. First, what is included in the category "drugs"? Is the author talking about illegal drug use, recreational drug use (which might include alcohol and cigarettes), or all uses of medication in general? Second, in what ways are drugs detrimental? Is drug use causing deaths (and is the author equating deaths from overdoses and deaths from drug related violence)? Is drug use changing the moral climate or causing the economy to decline? Finally, what does the author mean by "society"? Is the author referring only to America or to the global population? Does the author make any distinction between the effects on children and adults? There are just too many questions that the claim leaves open. The author could not cover all of the topics listed above, yet the generality of the claim leaves all of these possibilities open to debate.

Example of a narrow or focused thesis:

In this example the topic of drugs has been narrowed down to illegal drugs and the detriment has been narrowed down to gang violence. This is a much more manageable topic.

We could narrow each debatable thesis from the previous examples in the following way:

Narrowed debatable thesis 1:

This thesis narrows the scope of the argument by specifying not just the amount of money used but also how the money could actually help to control pollution.

Narrowed debatable thesis 2:

This thesis narrows the scope of the argument by specifying not just what the focus of a national anti-pollution campaign should be but also why this is the appropriate focus.

Qualifiers such as " typically ," " generally ," " usually ," or " on average " also help to limit the scope of your claim by allowing for the almost inevitable exception to the rule.

Types of claims

Claims typically fall into one of four categories. Thinking about how you want to approach your topic, or, in other words, what type of claim you want to make, is one way to focus your thesis on one particular aspect of your broader topic.

Claims of fact or definition: These claims argue about what the definition of something is or whether something is a settled fact. Example:

Claims of cause and effect: These claims argue that one person, thing, or event caused another thing or event to occur. Example:

Claims about value: These are claims made of what something is worth, whether we value it or not, how we would rate or categorize something. Example:

Claims about solutions or policies: These are claims that argue for or against a certain solution or policy approach to a problem. Example:

Which type of claim is right for your argument? Which type of thesis or claim you use for your argument will depend on your position and knowledge of the topic, your audience, and the context of your paper. You might want to think about where you imagine your audience to be on this topic and pinpoint where you think the biggest difference in viewpoints might be. Even if you start with one type of claim you probably will be using several within the paper. Regardless of the type of claim you choose to utilize it is key to identify the controversy or debate you are addressing and to define your position early on in the paper.