Rousseau’s moral and political philosophy is grounded in a largely overlooked virtue epistemology. This essay reconstructs this epistemology with a particular focus on Rousseau’s conception of how our capacity for sensation might be cultivated to develop the judgment and wisdom that distinguish the developed virtuous agent. It proceeds in three sections. The first section focuses on Rousseau’s conception of the first stage of development, and especially his sensationist claim that all knowledge originates in sensory impressions. The second section examines the maturing agent’s transition from mere sensation to the cultivation of the capacity for judgment, particularly focusing on Rousseau’s account of the agent’s shift from the passive reception of sensory impressions of discrete objects to the active and synthetic processes of comparison and association that give rise to complex ideas and to moral conceptions. The third section turns to Rousseau’s conception of the developed mind, focusing on his claim that the intellectual virtues not only require cultivation but are indispensible to the proper exercise of freedom that distinguishes the fully moral human being.