If a counterpart theorist’s understanding of the counterpart relation precludes haecceitist differences between possible worlds, as David Lewis’s does, how can he admit haecceitist possibilities, as Lewis wants to? Lewis (Philosophical Review 3–32, 1983; On the Plurality of Worlds, 1986) devised what he called a ‘cheap substitute for haecceitism,’ which would allow for haecceitist possibilities while preserving the counterpart relation as a purely qualitative one. The solution involved lifting an earlier (Journal of Philosophy 65(5):113–126, 1968; 68(7):203–211, 1971) ban on there (...) being multiple intra-world counterparts. I argue here that serious problems for ‘cheap haecceitism’ lurk very close to its surface, and they emerge when we consider the effect of using an actuality operator in our language. Among the most serious of the problems is the result that being the case in some possible world does not always suffice for possibly being the case. The result applies to any counterpart theory that employs a purely qualitative counterpart relation. The upshot is that if we are to admit haecceitist possibilities, as we should, then we must reject any purely qualitative relation as the one involved in the analysis of what might have been for an individual. (shrink)

Persistence through time is like extension through space. A road has spatial parts in the subregions of the region of space it occupies; likewise, an object that exists in time has temporal parts in the various subregions of the total region of time it occupies. This view — known variously as four dimensionalism, the doctrine of temporal parts, and the theory that objects “perdure” — is opposed to “three dimensionalism”, the doctrine that things “endure”, or are “wholly present”.1 I will (...) attempt to resolve this dispute in favor of four dimensionalism by means of a novel argument based on considerations of vagueness. But before argument in this area can be productive, I believe we must become much clearer than is customary about exactly what the dispute is, for the usual ways of formulating the dispute are flawed, especially where three dimensionalism is concerned. (shrink)

Many philosophers, following David Lewis, believe that we should look to counterpart theory, not quantified modal logic, as a means of understanding modal discourse. We argue that this is a mistake. Significant parts of modal discourse involve either implicit or explicit reference to what is actually the case, raising the question of how talk about actuality is to be represented counterpart-theoretically. By considering possible modifications of Lewis's counterpart theory, including actual modifications due to Graeme Forbes and Murali Ramachandran, we argue (...) that no coherent version of counterpart theory can provide a plausible representation of talk about actuality, and so, we conclude, counterpart theory should be rejected. (shrink)

David Lewis's modal realism claims that nothing can exist in more than one world or time, and that statements about how something would have been are to be analysed in terms of its counterpart. I first explain why the counterpart relation depends on de re modal statements in an intensional language, so that intuitive properties of similarity relations cannot be used to show that the counterpart relation is not an equivalence relation. I then look at test sentences in (the intensional) (...) natural language, and show that none of them provide compelling evidence that a counterpart semantics is needed. (shrink)

0. Logic is sometimes conceived as metaphysically neutral, so that nothing controversial in metaphysics is logically valid. That conception devastates logic. Just about every putative principle of logic has been contested on metaphysical grounds. According to some, future contingencies violate the law of excluded middle; according to others, the set of all sets that are not members of themselves makes a contradiction true. Even the structural principle that chaining together valid arguments yields a valid argument has been rejected in response (...) to sorites paradoxes. In each case, a deviant metaphysics corresponds to the deviant logic. Of course, if one is trying to persuade deviant metaphysicians of the error of their ways, one is unlikely to get far by relying on logical principles that they reject. But that obvious dialectical exigency stably marks out no realm of logic. Each logical principle has persuasive force in some dialectical contexts and not in others. We do better to admit that logic has metaphysically contentious implications, and embrace them ─ if we know what they are. (shrink)

Robert Stalnaker is an actualist who holds that merely possible worlds are uninstantiated properties that might have been instantiated. Stalnaker also holds that there are no metaphysically impossible worlds: uninstantiated properties that couldn't have been instantiated. These views motivate Stalnaker's "two dimensional" account of the necessary a posteriori on which there is no single proposition that is both necessary and a posteriori. For a necessary proposition is true in all possible worlds. If there were necessary a posteriori propositions, that would (...) mean that there were propositions true in all possible worlds but which could only be known to be true by acquiring empirical evidence. Consider such a purported proposition P. The role of empirical evidence for establishing P's truth would have to be to rule out worlds in which P is false. If there were no such worlds to be ruled out, we would not require evidence for P. But by hypothesis, P is necessary and so true in all metaphysically possible worlds. And on Stalnaker's view, the metaphysically possible worlds are all the worlds there are. So there can be no proposition that is true in all possible worlds, but that we require evidence to know. In this way, the motivation for Stalnaker's two dimensional account of the necessary a posteriori rests on his denying that there are metaphysically impossible Worlds. I argue that given his view of what possible worlds are, Stalnaker has no principled reason for denying that there are metaphysically impossible worlds. If I am right, this undercuts Stalnaker's motivation for his two dimensional account of the necessary a posteriori. (shrink)

A claim by David K. Lewis (1986) that his counterpart theory provides a semantics for intensional languages is critiqued by showing that basic principles of modal logic fail to be valid in counterpart theory & by investigating problematic counterpart-theoretical translations of instances of universal instantiation. From Lewis's postulate that individuals inhabit only one world & have counterparts in other worlds, it follows that the relation between an object & its counterparts is nontransitive & nonsymmetric; consequently, an object does not need (...) to have exactly one counterpart in any world. The failure of modal principles in counterpart theory is ascribed to the possibility that an object has no counterpart in a given world, whereas universal instantiation becomes invalid when an object has more than one counterpart in a given world. 3 References. Adapted from the source document. (shrink)

It has been claimed that counterpart theory cannot support a theory of actuality without rendering obviously invalid formulas valid or obviously valid formulas invalid. We argue that these claims are not based on logical flaws of counterpart theory itself, but point to the lack of appropriate devices in first-order logic for “remembering” the values of variables. We formulate a mildly dynamic version of first-order logic with appropriate memory devices and show how to base a version of counterpart theory with actuality (...) on this. This theory is, in special cases, equivalent to modal first-order logic with actuality, and apparently does not suffer from the logical flaws that have been mentioned in the literature. (shrink)