As you begin to formulate a thesis for your essay, think about the following distinction between topic and thesis. A topic is a general area of inquiry; derived from the Greek topos (place), "topic" designates the general subject of your essay. For instance, "Hamlet is not mad" would be a weak thesis but a good a topic for an essay. From a topic, many specific theses can be extracted and developed. A thesis is more specific and delimited; it exists "within" your topic. In your essay, you need to use an argumentative thesis.
In argumentative writing, the writer takes a stance and offers reasons in support of it. Crucial to any piece of argumentative writing is its thesis. The thesis arises from the topic, or subject, on which the writing focuses, and may be defined as follows:
A thesis is an idea, stated as an assertion, which represents a reasoned response to a question at issue and which will serve as the central idea of a unified composition.
If we've selected the question of Hamlet's madness as a topic, we need to define what constitutes "madness," and we might ask how "madness" functions in Hamlet. If Hamlet is not mad, how do we know he's sane? One possible thesis is:
Hamlet's madness is one of many disguises used to gain power over others. Because the line between madness and sanity is subject to change (depending on the context of one's actions), Hamlet's choice of disguise is both the most effective and the most volatile form of power in Shakespeare's play.
(Here, the second sentence is the thesis; the first establishes the basis of the claim.)
When you compose a thesis statement, think about how it satisfies the following tests:
1. Is it an idea? Does it state, in a complete sentence, an assertion?
2. Does it make a claim that is truly contestable and therefore engaging?
(Yes, because one could also argue that Hamlet is mad, or that his feigned madness is an ineffective form of power.)
3. Are the terms you are using precise and clear?
(Key terms here seem to be: "madness," "disguise," "power," and the idea that madness is both an "effective" and a "volatile" means of power.)
4. Has the thesis developed out of a process of reasoning?
Once these questions have been satisfactorily answered, use the resulting thesis to organize your evidence and begin the actual writing. As you do so, bear in mind the following questions:
1. What is my purpose in writing? What do I want to prove?
(Notice the explicit purpose in the thesis statement: it does not merely point out that Hamlet's sanity is questionable; instead, the thesis takes a position on this issue, and then answers the question "So what?")
2. What question(s) does my writing answer?
3. Why do I think this question is important? Will other people think it equally important?
4. What are my specific reasons, my pieces of evidence? Does each piece of evidence support the claim I make in my thesis?
5. Where does my reasoning weaken or even stop? Am I merely offering opinions without reasoned evidence?
6. How can I best persuade my reader?