A thesis statement is a debatable argument. It is not a topic sentence or observation

• Fact or observation: The poem contains medieval allusions.
• Thesis: The poem uses medieval allusions to invoke a utopian past through which to critique the contemporary political climate.

A strong thesis has 3 parts: the What, Where/How, and the Why (a.k.a “So What?”)
1) What do you see?:  This is your insight
2) Where do you see it?  How is it being done?: This is where you use specific elements from the work to support your insight
3) Why is this relevant? So What?: This is where you explain why your insight is relevant, where you make an argument about what the work is saying/doing with and through your insight. This is where you push your insight to larger conclusions about the work as a whole.

The Purpose of a Thesis: A thesis statement presents the argument to the reader and serves as a guideline for the writer.

An analytical essay should prove its thesis statement.  This means that is it not enough to point out interesting elements in a text or merely show insightful readings of these elements. Instead, you must use these readings to prove a larger point, your thesis, about the work.  Thus, every explication and piece of textual support should work to serve the larger goal of proving your three-pronged thesis and, and this is the hardest part, addressing the “so what” factor.Edit