If you argue for or against a policy, words such as "should" or "must" clearly indicate your purpose. An argument of value expresses your approval or disapproval of an issue. Note these examples:
-- The government should never torture political prisoners because of constitutional prohibitions, ethical objections and overall ineffectiveness.
-- Requiring uniforms in public schools violates freedom of choice and personal aesthetic tastes.
Both statements offer opinions and provide a preview of the main arguments that will support the thesis. Other argumentative thesis statements might involve interpretation, evaluation or cause-and-effect relationships.
In an analysis, you break down a topic into its parts. Although you can argue cause-and-effect relationships, you can also analyze them. For example, an analytical thesis statement might simply list causes or effects:
-- Video games can affect children in many ways by increasing eye-hand coordination, stimulating perceptual speed, encouraging aggressive behavior and promoting social isolation.
-- The growing epidemic of childhood obesity may result from environmental factors, parental choices and genetic predispositions.
Note that the first thesis statement considers both positive and negative aspects, rather than arguing against video games. The second statement previews possible causes of obesity. Both thesis statements clearly encapsulate the essays that follow.
An explanatory essay may simply discuss a topic. For example, a comparison/contrast could simply describe similarities and differences rather than build an argument. Consider this thesis statement:
-- Recent studies suggest that Millennials and Baby Boomers have different perspectives about technology, work ethic and family structure.
Without presenting an argument or point of view, this thesis organizes three categories of differences and prepares the reader for the essay to follow.
Although your original thesis provides a rough guide for the first draft of your research paper, you may need to revise it before your final draft. Perhaps you have overgeneralized and need to add qualifiers. For example, you may realize that "many" Millennials and Baby Boomers differ, but not "all." In his 2011 article "Revising Your Thesis," Chuck Guilford suggests that the writing process may lead to a heightened awareness of your topic and a realization that the original thesis needs tweaking. The resultant thesis may more accurately reflect your opinion and the organization of the essay.