This course is about mental parts, intrapsychic conflict, rationality, and responsibility. We’ll begin by reviewing claims that minds have divisions or parts that operate with different processing principles and/or compete in some interesting sense, with an eye to clarifying what these claims mean as well as whether the claims are true. We next turn to the question of how best to understand mental conflict: Do mental parts compete via non-rational “force” or by some other means? The next topic is normative: How should beliefs or motivations arising from mental parts be rationally arbitrated. Here we’ll find recent work on peer disagreement, higher-order evidence, and metacognition to be relevant. Finally, we turn to moral responsibility. Is a person morally responsible when mental parts issue in problematic beliefs or actions or when the person fails to adequately monitor and supervise mental subsystems? We’ll take up this question as we consider topics at the center of recent philosophical debates, including responsibility for mistakes, beliefs, and implicit biases.