Kant was a German metaphysician who shook the foundations of Western philosophy. In his Critique of Pure Reason, Kant proposed that objective reality is known only insofar as it conforms to the essential structure of the knowing mind and that things beyond experience are unknowable. He thus concluded that the existence of God, freedom, and immortality can be neither affirmed nor denied on theoretical grounds. His system of ethics is based the “categorical imperative,” which is what? Discuss