 According to Goodman, pictorial symbol systems differ from linguistic ones in being analog and relatively replete, an analog system being one that is syntactically and semantically dense. (For reasons of space we shall not discuss the relationship between analog and dense; see Lewis 1971 and Haugeland 1981.) A pictorial system is syntactically dense because it provides for a dense set of pictorial characters, in other words, a set containing infinitely many pictures “so ordered that between each two there is a third” (Goodman 1968: 136), and it is semantically dense because it provides for a dense set of classes of denotata. (By contrast, the Arabic numeral system for denoting the natural numbers provides for infinitely many characters—“1”, “2”, “3” …, “11”, “12”, “13” …, etc.—but there is a “gap” between each numeral and its successor, and between each of the corresponding natural numbers and its successor: the system is articulate, not dense.) Finally, a pictorial system is relatively replete because relatively many properties of a picture are relevant to its interpretation: