 The second version of monism allows us to accommodate the phenomena considered in  section 1.1  while staying much closer to the picture sketched in the introduction to  section 1.  On this view, the data can be explained by appeal to a single space of possible worlds and a single notion of truth in a world. The proposition semantically expressed by a sentence containing a proper name or natural-kind term is a function from individual worlds to truth-values. The proposition expressed by ‘Phosphorus exists,’ e.g., is a function that assigns the true to those worlds where Venus exists and the false to the other worlds. (If the reference of ‘Phosphorus’ was determined by a reference-fixing description together with the facts about which entity meets the description, then that fact itself is not a semantic fact, but a metasemantic one, i.e., it does not concern the question of what the meaning of the word is, but the question of how the meaning of the word is determined.) What explains the impression that a sentence like (1) expresses an a posteriori claim is the fact that the proposition asserted by a typical utterance of the sentence is not the one that is semantically expressed by it, but a different proposition that is contingent and can only be known empirically.