His Mark: Kantians, enlightenment philosophy His Major: Epistemology, Metaphysics, Ethics Logic His Concept: Categorical imperative Transcendental Idealism, Synthetic a prior n Noumenon, Sapere aude, Nebular hypothesi8  His Mark: Kantianism, enlightenment philosophy  His Major: Epistemology, Metaphysics, Ethics, Logic  His Concept: Categorical imperative, Transcendental Idealism, Synthetic a priori, Noumenon, Sapere aude, Nebular hypothesis