 Nietzsche’s talk about the creation of values challenges philosophical common sense. It is common, if not altogether standard, to explain values by contrasting them against mere desires. Both are positive attitudes toward some object or state of affairs (“pro-attitudes”), but valuing seems to involve an element of objectivity absent in desiring. (Consider: If I become convinced that something I valued is not in fact valuable, that discovery is normally sufficient to provoke me to revise my value, suggesting that valuing must be responsive to the world; by contrast, subjective desires often persist even in the face of my judgment that their objects are not properly desirable, or are unattainable; see the entries on  value theory  and  desire.)  Nietzsche challenges this basic philosophical conception when he treats value as “created” rather than discovered in the world: