Abstract

Kantian ethics is traditionally seen as grounded in unchanging, universally binding, and a priori knowable principles. I argue that this picture is incomplete: Kant grounds his ethics not only in categorical moral principles, but also in regulative moral ideas of reason. On Kant's account, moral ideas contain metanormative moral content that outstrips agents' cognitive resources: they are unattainable in their entirety, indeterminate and unbounded, and cannot be directly represented. I show how Kant's ethics need not be supplemented with external resources in order to explain moral change, but can instead rely on resources internal to it: moral ideas. In both the theoretical and moral Kantian systems, ideas of reason regulatively guide the respective acquisition of scientific and moral knowledge, allowing for the possibility of moral as well as epistemic progress.