"In what sense exactly are there many worlds? What distinguishes real worlds from unreal ones? What are they made of? How are they created? What role do symbols play in their creation? And how is the creation of worlds related to recognition?" These questions are explored by Nelson Goodman in his book "Ways of Worldmaking." He begins his investigation with an explicit reference to Cassirer, from whom he adopts the idea of generating worlds with symbols: "Cassirer seeks (for a unity of all world versions) through a transcultural exploration of the development of myth, religion, language, art, and science. My approach, on the other hand, is one of an analytical exploration of types and functions of symbols and symbol systems." The worlds that Goodman deals with are real worlds: "We are not talking about many possible alternatives to a single world.".