  Carr uses the concept of the relativity of thought, which he traces to Marx and other modern theorists, to show that standards by which policies are judged are the products of circumstances and interests. His central idea is that the interests of a given party always determine what this party regards as moral principles, and hence, these principles are not universal. Carr observes that politicians, for example, often use the language of justice to cloak the particular interests of their own countries, or to create negative images of other people to justify acts of aggression. The existence of such instances of morally discrediting a potential enemy or morally justifying one’s own position shows, he argues, that moral ideas are derived from actual policies. Policies are not, as the idealists would have it, based on some universal norms, independent of interests of the parties involved.