The thesis is the main point of your essay. Often, the thesis is stated clearly in one or two sentences at the end of the essay's introduction. This is called a thesis statement.
Does the thesis have to come at the end of the introduction?
There are exceptions to almost every rule of writing, including this one. There are times when the thesis statement is not presented until the very end of the essay--especially when there is a "surprise" aspect to the essay that might be ruined if the thesis statement came earlier.
However, unless you have a good reason not to, putting your thesis statement at the end of the introduction is a good idea because it often prevents the reader from getting confused about your essay's purpose (besides, it usually makes English instructors happy).
How do I know if my thesis statement is a good one?
Ideally, your thesis statement will be specific enough to give your reader a clear sense of what your entire essay is going to discuss.
The following thesis statement is much too vague:
Men and women are different.
Obviously, the reader would have no clue about which differences are going to be discussed, and the essay certainly isn't going to discuss all of them. The following thesis statement is better, but still a bit vague:
Men and women communicate differently.
Now the reader at least knows the essay will discuss communication differences. However, the thesis statement could be clearer still:
Whereas men tend to focus on the literal aspect of what is being said in a conversation, women often "read between the lines" and focus more on intonation and body language.
Now the reader has a clear sense of where the essay is going, but he or she may have one question remaining: "So what?" Often, a good thesis statement will begin to reveal the "so what?" of the essay:
Whereas men tend to focus on the literal aspect of what is being said in a conversation, women often "read between the lines" and focus more on intonation and body language; this phenomenon may significantly contribute to the high divorce rate in the United States.
I don't know what my thesis is yet, so how can I write my essay?
Do not be upset if you don't know precisely what your thesis is before you start writing. Very often writers don't know exactly what their thesis is until they have written a complete draft.
It is ok to start with a vague or tentative thesis statement in your first draft with the idea that you will revise it into something more specific. For example, a writer might start out with the following tentative thesis:
Recycling is important.
Then, after working through a draft, the writer may realize that the essay really explains how recycling paper can help save forests, which in turn can prevent certain species of animals from becoming extinct. It is important for the writer to then go back and revise the thesis statement so that it fits the essay better:
Although most people recognize that recycling is important, many do not realize that it can be directly responsible for the survival of a species.
Riminder: Before you turn in any essay double check to make sure that the thesis statement fits the essay. In other words, every paragraph in the essay should be discussing the topic presented in the thesis statement. Be prepared to revise the thesis statement or the essay so that the two fit together.
It is often easier to change the thesis statement than the rest of the essay, but if you do so, you may have to revise parts of the essay to make it fit the thesis.
Another good idea: Before you turn in your essay, go back and reread the explanation of the assignment provided by your instructor. Make sure that your thesis statement answers the question posed in the assignment and/or fulfills the requirements of the assignment (i.e. if the assignment asks you to compare and contrast two ideas, your thesis statement should compare and contrast two ideas).