Rational Causation is about rationality—the capacity to appreciate and be guided by reasons. This is a big topic, straddling the philosophy of mind, the philosophy of action, and epistemology. Marcus has fascinating views to defend about each of these subjects, and he draws them all together into a deep and illuminating account of rationality's nature and structure. The book offers just what one hopes for, but rarely finds, in work on rationality: the combination of a broad perspective with detailed and rigorous engagement of a range of specific issues. A superlative achievement.