This text examines the boundary between philosophy and formal logic in Kant and Hegel. It takes up the particular category of ‘quantity’ as a point around which to explore Kant’s and Hegel’s larger architectonic concerns. Analysis of the relation in Kant between quantity in formal logic and in his transcendental logic reveals two complementary but distinct approaches that preserve the boundary between philosophy and formal logic. By contrast, in Hegel’s Science of Logic we find both a novel approach to the traditional treatment of quantity in logic, and a reconstruction of the relation of logic to all other determinations of thought. By basing its examination of the relation of formal logic and philosophy in Kant and Hegel on a detailed analysis of quantity, Logic and the Limits of Philosophy in Kant and Hegel provides a resource for an historically informed interpretation of the revolutions in logic that marked the onset of our digital age.