Andrew Thomas

This thesis argues that we should consider extended modal realism as a new player in the debate about non-existence. The primary aim is to show that extended modal realism is a viable theory when it comes to solving problems of non-existence. At times I will argue that extended modal realism has advantages over Lewisian modal realism when it comes to examining the problems of non-existence, not only in the case of problems relating to thought but also problems concerning truth as well. However, I do not intend for the proposed advantages of extended modal realism to be presented as knockdown arguments against other strategies. Not only do I argue that extended modal realism is viable when it comes to solving these problems, but I also make adjustments and additions to the theory that supports the conclusion of this thesis, and I argue that these are improvements to the modal realist theory. I include arguments for a new theory of existence that removes the need for the extended modal realist to rely on set-theoretic notations to understand existence, which I consider problematic. I argue for the revival of the Lewis-Rosen proposal for truth-making and a semantic instrumentalist theory of thought, both of which naturally accompany extended modal realism. Throughout this thesis, I will comment on the proposals and strategies of other authors, and some of these comments will be critical. At this very early stage, I want to clarify that this thesis's success does not rest on showing that all other competitor theories fail. I only include critical comments to situate extended modal realism within the landscape of viable positions that are available for one to occupy.

Kriegel described the problem of intentional inexistence as one of the ‘perennial problems of philosophy’, 307–340, 2007: 307). In the same paper, Kriegel alluded to a modal realist solution to the problem of intentional inexistence. However, Kriegel does not state by name who defends the kind of modal realist solution he has in mind. Kriegel also points out that even what he believes to be the strongest version of modal realism does not pass the ‘principle of representation’ and thus modal realism is not an adequate solution to the problem of intentional inexistence. In this paper, I respond to Kriegel by defending a modal realist solution that he did not consider in 2007, called ‘extended modal realism’. EMR is a version of modal realism where possible worlds are not completely isolated as they are under the Lewisian model. Rather, under EMR worlds are, in a way, spatiotemporally related. The fact EMR worlds are related allows EMR to sufficiently pass the principle of representation and thus can be deemed a legitimate solution to the problem of intentional inexistence. I conclude that either EMR can pass the principle of representation in some cases or, and I think the more sensible option, we give up on the principle of representation altogether.