A thesis statement is a declaration of the writer's purpose behind writing an essay or report. More often than not, the thesis statement is placed in the opening, introductory paragraph of an essay. Many teachers like to force it as the last sentence of the first paragraph. It is always a single sentence that declares what you, the writer, are going to prove over the course of the essay. The best thesis statements are thesis statements that propose something bold, creative, or new. When a person is reading your essay, they should always be able to see how the current paragraph relates back to the thesis. That single sentence at the beginning guides the rest of the paper, which is why thesis statement = purpose.