Think of yourself as an associate of a jury, listening to an attorney who is presenting an argument that is opening. You need to know as soon as possible whether the lawyer believes the accused to be guilty or otherwise not guilty, and exactly how the lawyer plans to convince you. Readers of academic essays are just like jury members: before they usually have read too far, they want to know what the essay argues in addition to the way the writer plans to make the argument. After reading your thesis statement, the reader should think, “This essay will probably attempt to convince me of something. I’m not convinced yet, but I’m interested to see how I may be.”
An thesis that is effective be answered with a simple “yes” or “no.” A thesis is not a subject; nor is it a fact; neither is it an impression. “cause of the fall of communism” is an interest. “Communism collapsed in Eastern Europe” is a fact known by educated people. “The fall of communism is the greatest thing that ever happened in Europe” is an impression. (Superlatives like “the best” almost always lead to trouble. You can’t really weigh every “thing” that ever happened in Europe. And think about the fall of Hitler? Couldn’t that be “the best thing”?)
A good thesis has two parts. It will tell what you plan to argue, plus it should “telegraph” the method that you plan to argue—that is, what particular support for your claim is going where in your essay.
Steps in Constructing a Thesis
First, analyze your sources that are primary. Try to find tension, interest, ambiguity, controversy, and/or complication. Does the author contradict himself or herself? Is a point made and later reversed? Which are the deeper implications of the author’s argument? Figuring out the why to 1 or even more among these questions, or to related questions, will put you on the road to developing a working thesis. (with no why, you probably have only show up with an observation—that you can find, by way of example, many metaphors that are different such-and-such a poem—which is not a thesis.)