This thesis provides answers for two questions, the first being “what is humor?” and the second being “how can humor be valuable?”. The first part of the thesis determines what a theory of humor should contain while addressing concerns that deal with the subjectivity of humor. The second part examines four major theories of humor: the Incongruity Theory, the Superiority Theory, the Relief Theory, and the Play Theory. The examination includes assessing the necessary and sufficient conditions of what constitutes humor under each theory and raising objections that render each theory inadequate in specific circumstances. Lastly, this thesis argues for the Play Theory and proposes a change to the theory in the third part to avoid objections. The third part also ends by arguing for the value of humor and claims that the value of humor is not limited to one specific type of humor.