swans on Earth are blue'. 8 to express a set of worlds, make it easier to express here in Cosmo than anywhere else. In fact, those (like Lewis) who identify all propositions with sets of Lewis-worlds are under pressure to reject claims like (9) even if they do identify contingency-inducing quantification with de re restricted quantification! For if the proposition that no swans on Earth are blue is a set of Lewis-worlds, which set is it? If we help ourselves to a counterpart relation, there are a few natural candidates: the set of Lewis-worlds in which some counterpart of Earth lacks blue swans; the set of Lewis-worlds in which every counterpart of Earth lacks blue swans; the set of Lewis-worlds in which there is exactly one counterpart of Earth, which lacks blue swans. Whichever we choose, we will be committed to the claim that whenever the counterparts of x are exactly the counterparts of Earth, the proposition that there are no blue swans on x is identical to the proposition that there are no blue swans on Earth. So if Earth-Prime and Earth happen to be similar enough to share exactly the same counterparts, people on Earth-Prime who utter the words 'some swans on Earth are blue' do thereby say that there some swans on Earth are blue!17 I think this is a reductio of the doctrine that all propositions can be identified with sets of Lewis-worlds. Let me reiterate the arguments I have given. First, since no swans on Earth are blue, anyone who says that some swans on Earth are blue says something false, but people on EarthPrime who utter the words 'some swans on Earth are blue' do not thereby say anything false. Second, saying that some swans on Earth are blue requires referring to Earth, which normally requires being spatiotemporally or causally related to Earth.18 However, someone 17Similarly, if Cosmo-Prime and Cosmo have exactly the same counterparts-if, for example, each has all and only Lewis-worlds as counterparts, as entertained above-then the proposition that there are no blue swans in Cosmo-Prime is the p