The central aim of this course is to help you to reason better when deciding what to believe and what to do. This course provides the tools you need, drawing from several areas: cognitive psychology, behavioral economics, logic, probability, and decision theory. We will consider empirical evidence about heuristics and biases—spontaneous judgments that can be predictably irrational. And we will study what good deductive, causal, and probabilistic reasoning looks like. At the end of the course, students should be able to identify common cognitive pitfalls and to master techniques that help them avoid these pitfalls or mitigate their effects. In this sense, the goal of the course is entirely practical: to develop effective reasoning skills with clear applications in your personal and professional lives. The course is open to students from all areas of study interested in improving their reasoning ability and their ability to construct and recognize compelling arguments. These skills may be helpful in a wide variety of subjects and extra-academic pursuits. But since proper reasoning is the centerpiece of philosophy, students intending to major or minor in philosophy must take this course.