The main idea. The argument of an essay. The thesis. It’s a tricky thing to define “thesis” because theses come in all sorts of shapes and sizes. A thesis can be a sentence, two sentences, perhaps even an entire paragraph. Every thesis, though, regardless of where in an essay it appears, does a few important things:

1. A thesis acts as a unifying idea for every piece of evidence in an essay.
2. A thesis results from research in addition to the writer’s own beliefs or opinions.
3. A thesis answers a specific question.

There are lots of ways to create a successful thesis because good theses come in all sorts of varieties. What all successful argumentative theses have in common, though, are the following characteristics:

• A good thesis statement is arguable. In other words, the writer’s claim might be challenged or opposed.
• A good thesis statement expresses one main idea, and that idea controls what is said, what is left out, and how the delivered evidence is organized.
• A good thesis statement is specific and insightful.
• A good thesis statement encourages discussion.
• A good thesis statement is supported by relevant evidence. Every paragraph should contribute to proving the thesis to be valid

Developing a Thesis

• Define the Rhetorical Situation: The key to developing an appropriate thesis is to begin by examining the rhetorical situation: What is the purpose of your essay (e.g., to inform, to persuade, to analyze)? To whom are you writing (e.g., classmates, members of a particular interest or age group)?
• Choose a Topic: Based on the purpose of and audience for your essay, what is an appropriate topic? Moreover, what is an appropriate topic that also interests you personally?
• Start with What You Know: What do you know about your topic? What have you heard on the news about your topic? Do you have personal experiences related to your topic? If so, what are they?
• Research What You Don’t Know: Start by searching the library databases (e.g., with Academic Search Premier or WorldCat). It’s best to begin by searching with your general topic and then refining your initial results. Gather a variety of sources and start reading. Some general reading on your topic will help you with the next step.
• Take a Position: Before you take a position, be sure you have done ample reading and you are aware of the various positions regarding your topic. Most issues have more nuances than basic understandings suggest. It is not enough to be “for” or “against” an issue. You must be able to support your position with evidence and logical reasoning, and research can help you in this regard.

Refining Your Thesis

After choosing a position, in forming reasoning for your decision, you must be clear and specific. You must be able to substantiate your claim using authoritative, credible, and relevant source material. Theses tend, in draft form, to begin as general and to become more specific as you do more research. Let’s look at how we might turn a weak thesis into a strong thesis.

Weak thesis:

On April 20, 2010, the explosion of the Deepwater Horizon oil platform caused the largest man-made disaster in U.S. history.

This thesis has a serious problem for two reasons: it doesn’t actually make an argument. It simply states an unproven fact: that the Deepwater Horizon oil spill is the largest man-made disaster in U.S. history. In order to be successful, a thesis must be arguable and supported by evidence. If we consider that a thesis must be a statement that reasonable people may disagree with and a position substantiated with credible evidence, this thesis is problematic because no one will disagree with the date the oil spill occurred and because the claim that the oil spill was the largest man-made disaster in U.S. history is unsubstantiated.

A still weak thesis:

Many people are to blame for the oil spill that resulted from the explosion of the Deepwater Horizon oil platform, which caused the largest man-made environmental disaster in U.S. history.

This thesis is better than the first because it does more than state a fact, but it is still problematic: it is not specific enough, and the claim that the Deepwater Horizon oil spill is the “largest man-made” disaster is still unsubstantiated. This thesis might, instead, attempt to answer the following questions: “Who is to blame for the Deepwater Horizon oil spill?” and “Why might it be considered the largest man-made environmental disaster in the U.S. history?” A successful thesis must be arguable and must answer a specific question.

A better thesis:

BP, President George W. Bush, President Barack Obama, Republicans in Congress, Democrats in Congress, and every citizen in the United States share the blame for the oil spill that resulted from the explosion of the Deepwater Horizon oil platform, which some consider the largest man-made environmental disaster in U.S. history, and in order to prevent another such disaster, Congress must develop better regulations, oil companies must enact better maintenance procedures, and Americans must decrease their dependence on oil.

This thesis is certainly more specific, but it’s trying to do too much. Proving that all parties mentioned are to blame for the Deepwater Horizon oil spill and that the solutions mentioned will prevent another oil disaster requires covering a lot of ground. A good thesis is arguable and specific, but also has one main idea. This thesis has too many main ideas.

An even better thesis:

Oil companies and the federal government share responsibility for the Gulf oil spill that resulted from the April 2010 Deepwater Horizon explosion.

This thesis works better than the previous versions because it’s arguable, specific, and focused on one main idea, but not so specific as to greatly limit discussion of the topic. From an essay based on such a thesis, readers will expect evidence that supports the claim that oil companies and the federal government hold joint responsibility for the Gulf oil spill.