  In Meaning and Necessity, Rudolf Carnap suggests that a Leibnizian possible world is represented by his state-descriptions: a class of sentences containing, for every atomic sentence, either it or its negation. In other words, for each possible world there is a series of propositions that will fully describe that world. The idea of a possible world as being such a set of sentences or propositions leads naturally to the notion of a “world-book,” a term employed by Alvin Plantinga (The Nature of Necessity). Lest such devices seem anachronistic, it should be pointed out that, in the fascinating conclusion to the Theodicy, Leibniz speaks in a similar way; indeed, Leibniz's parable is something that one might imagine has come straight from Jorge Luis Borges (cf. “The Library of Babel”). The story concerns Theodorus, a high priest present when Sextus Tarquinius complains to Jupiter about his fate.  (Sextus was the son of the last king of Rome, whose crime of raping Lucretia so incensed Brutus that he led a revolt that ultimately abolished the monarchy and began the Roman Republic.) Theodorus is moved by Sextus' complaint and is sent to receive instruction at the temple of Pallas Athena where he is shown “the palace of the fates.” According to Athena, “Here are representations not only of that which happens but also of all that which is possible. Jupiter, having surveyed them before the beginning of the existing world, classified the possibilities into worlds, and chose the best of all.” (Theodicy §414: G VI 363/H 370) She continues,