The thesis is the essence of an argumentative essay. In a single, clear sentence, it sums up what point you are trying to make. The thesis statement should assert a position on a particular issue -- one that a reader can potentially argue against. Therefore, the thesis cannot be a fact. For example, if a professor assigns the general topic of war, you can formulate the following thesis statement: "The United Nations must be redesigned because it is currently incapable of preventing wars." The rest of your essay serves to explain and provide evidence in support of your thesis statement.