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.