This chapter examines Immanuel Kant's ethics, and particularly his views on reason and faith. According to Thomas Aquinas, there were two avenues whereby men could come to possess knowledge: the way of reason and the way of faith, of faith in revelation. Unlike Aquinas, Kant entertains not two faculties, but a single faculty in two employments. The chapter considers Kant's motives, and what he advanced as justifications, for treating the sources of knowledge and of moral behavior not as two separate faculties, but as different employments of a single faculty, reason. It offers a general account of Kant's moral philosophy, and more specifically his account of reason and his argument that men are obliged to obey the moral law. It also suggests that the duality of obligation and motivation is present in Kant's ethics and compares Kant's ideas with those of Richard Peters regarding human behavior.