TL;DR:
A thesis is one or two sentences that make a claim someone could reasonably disagree with, and say why you believe it.
Test it: Is it arguable? Is it specific? Does it preview the reasons your essay will give?
Revise in stages: topic, then opinion, then opinion with reasons, then a thesis that admits the strongest objection.
A teacher hands back your essay with one comment next to the first paragraph: 'What is your argument?' You thought you had one. You wrote that school start times are an important issue that affects many students. Nobody could disagree with that sentence, and that is exactly what is wrong with it. A thesis has to take a side.
What a thesis does for an essay
A thesis statement is the main claim of your essay, in one or two sentences, usually at the end of the introduction. It tells the reader what you will prove. It also tells you what to include: every paragraph must support the thesis or answer an objection to it. Writing without one produces a pile of facts about a topic instead of an argument.
A topic is what the essay is about. A thesis is what the essay says about it. 'School start times' is a topic. 'High schools should start later because...' is a claim.
Three tests every thesis should pass
Arguable. A reasonable person could disagree. If everyone nods, it is a fact or a truism, not a thesis.
Specific. It names who, what and how much, not just 'good' or 'bad' or 'important'.
It previews the reasons. The reader should see roughly what your main points will be.
What you need before you start
You do not need a perfect thesis before you read your sources, but you need a question. 'What is the best time for high schools to start?' is a question. Write it down, collect evidence on both sides, and pick the answer you can best support. Your first thesis is a working draft, and it is normal to change it after you see what the evidence supports.
Step by step
Start with a question: Turn the topic into a question with more than one defensible answer.
Answer it in one sentence: Say what you think. Use a verb that takes a position, such as 'should', 'causes', 'outweighs' or 'fails'.
Add because: Give your main reasons, in the order you will present them. Two or three is plenty.
Sharpen the words: Replace vague words with exact ones. Say which schools, which time, which effect.
Test it against the three questions: Could someone disagree? Is it exact? Does it show the reasons?
Account for the best objection: If there is a strong counterargument, name it in a short clause and say why your claim still stands.
A worked example: school start times
Here is the same thesis improved in five stages.
Draft | Thesis | What is wrong or better |
|---|---|---|
1 | School start times are an important topic that affects many students. | A topic, not a claim. Nobody can disagree. |
2 | School should start later. | Arguable now, but vague. Which schools? How much later? Why? |
3 | High schools should start later because students are tired. | Better. It names the schools and gives a reason, but 'tired' is vague and the reason is thin. |
4 | High schools should start no earlier than 8:30 a.m., because teenagers' body clocks tend to run later, so early classes catch them when they are least alert. | Specific time, specific group, a clear reason. Missing the cost objection. |
5 | Although later starts complicate buses and sports, high schools should start no earlier than 8:30 a.m., because teenagers' body clocks run later and early classes catch them least alert. | Arguable, specific, previews the reason, and admits the strongest objection. |
Run the three tests on draft 5. Arguable: someone could say that start times should stay as they are. Specific: it names high schools, a time, and a group. Previews the reasons: the reader expects a body paragraph about teenage body clocks and alertness, and another that deals with buses and sports. A reader can now predict the shape of your essay, which is a sign the thesis is working.
Notice what changed from draft 1. Each revision either took a side, narrowed the claim, or added a reason. None added a statistic. The evidence comes later, in the body, where each paragraph can support one of the reasons.
Mistakes to avoid
Announcing instead of arguing. 'This essay will discuss school start times' is a plan, not a claim.
Stating a fact. 'Many high schools start before 8:00' may be true, but a reader has nothing to argue with.
Asking a question. 'Should school start later?' is where you begin, not where you end.
Being too big. 'Education needs reform' cannot be proven in one essay.
Using 'I think' as a crutch. Your name on the essay already says it is your view. State the claim directly.
Listing three vague reasons. Choose the strongest two or three and make them specific.
Your plan for this week
Pick one essay prompt you have now or had recently and write it as a question.
Write five drafts of your thesis using the stages above, even if some are bad.
Run the three tests on your best draft and rewrite until it passes all of them.
Write one topic sentence for each reason in your thesis. The article on topic sentences that guide the reader, shows how.
Read your thesis aloud to someone and ask them what they expect the essay to say. If they guess right, you have a working thesis.
If you are wondering how to organise the paragraphs that follow, see the five-paragraph essay and when to move past it.
Frequently asked questions
Does a thesis have to be one sentence?
Not necessarily. One or two sentences is typical. What matters is that it is clear and complete.
Can I change my thesis after I start writing?
Yes, and you often should. If the evidence points somewhere else, revise the thesis to match, then revise the paragraphs to fit it.
Where does the thesis go?
Usually at the end of the introduction, so the reader meets it before the first body paragraph. Check what your teacher expects.
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