A thesis statement defines the scope and purpose of the paper. It needs to meet three criteria:
1. It must be arguable rather than a statement of fact. It should also say something original about the topic.
2. It must be limited enough so that the paper develops in some depth.
3. It must be unified so that the paper does not stray from the topic.
4. Statements such as "In this essay I will discuss " or "I will compare two stories in this paper" or "I was interested in Marji's relationship with God, so I thought I would talk about it in this essay" are not thesis statements and are unnecessary, since mentioning the stories in the introduction already tells the reader this.