Immanuel Kant's criticisms of the spurious principles of morality are best understood as parts of a sole survivor argument. Criticisms of mistaken views can be part of an argument to support a philosopher's own position. Henry Sidgwick is credited with having shaped a widely held view of the main difference between ancient and modern ethics. In the Groundwork Kant argues that a formal moral law is the basic law of morality. In the Groundwork (G IV 442-3) Kant divides heteronomous principles in two ways. One division is between empirically-based principles and rationally-based principles. The other division is between principles based on something internal to us and principles based on something external to us. Kant concentrates on principles about perfection, and begins by objecting to the ontological conception of it. Kant's basic argument against empirical views rests on the argument that moral principles must hold universally, for all rational beings.