Making a world version is difficult. Acknowledging a great number of them does not make it easier. The hard work lies, for example, in creating a constructional system that overcomes the problems of its predecessors, is simple, uses well-entrenched predicates, or successfully replaces them with new ones (which is even harder), allows us to make useful predictions and so on. For Goodman, scientists, artists, and philosophers are faced with analogous problems in this.