Friedrich Jacobi held a position of unparalleled importance in the golden age of late eighteenth and early nineteenth century intellectual history. Nonetheless, the range and style of his thought and its expression has always posed interpretative challenges that continue to hinder his reception. This volume introduces and evaluates Jacobi's pivotal place in the history of ideas. It explores his role in catalyzing the close of the Enlightenment through his critique of reason, how he shaped the reception of Kant's critical philosophy and the subsequent development of German idealism, his effect on the development of Romanticism and religion through his emphasis on feeling, and his influence in shaping the emergence of existentialism. This volume serves as an authoritative resource for one of the most important yet underappreciated figures in modern European intellectual history. It also recasts our understanding of Fichte, Hegel, Kierkegaard, and others in light of his influence and impact.