This book develops the foundations of an ethics of mind by investigating the responsibility that is presupposed by the requirements of rationality that govern our attitudes. It thereby connects the most recent research on responsibility and rationality in a unifying dialectic.How can we be responsible for our attitudes if we cannot normally choose what we believe, desire, feel, and intend? This problem has received much attention during the last decades, both in epistemology and ethics. Yet, its connections to discussions about reasons and rationality have been largely overlooked. The book has five main goals. First, it reinterprets the problem of responsibility for attitudes as a problem about the normativity of rationality. Second, it connects substantive and structural rationality by drawing on debates about responsibility. Third, it supports recent accounts of the normativity of rationality by explicitly defending the view that epistemic reasons and other ‘right‑kind’ reasons are genuine normative reasons, and it does so by drawing on recent discussions about epistemic blame. Fourth, it breaks the stalemate between rationalist and voluntarist accounts of mental responsibility by proposing a hybrid view. Finally, it argues that being irrational can warrant moral blame, thus revealing an unnoticed normative force of rational requirements.Responsibility for Rationality is an original and essential resource for scholars and advanced students interested in connecting strands of normative theory within epistemology, metaethics, and moral psychology.The Open Access version of this book was published with the support of the Swiss National Science Foundation.