Using logical and mathematical tools, formal semantics answers the following questions: Why do sentences mean what they mean? How is reasoning possible? How does language structure our understanding of time, change, knowledge, morality, identity, and possibility? We will assess formal semantics as a theory of linguistic meaning and reasoning by comparing its predictions with linguistic and psychological evidence. We will also examine its philosophical assumptions. This course is well suited for students interested in computer science, linguistics, logic, mathematics, or philosophy. (Some prior familiarity with formal logic is recommended, but not required.)