Existence, actuality and logical pluralism
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This work considers data about the intentional nature of human cognition, and traces their consequences for debates in the philosophy and epistemology of logic, and metaphysics. The first part of this work, comprising its first three chapters, investigates the prospect of revising logic in light of de re intentionality, that is, more precisely, in light of the fact that via their cognitive abilities agents can relate to objects that do not exist. We will consider two candidate systems for logical revision, expressions of two forms of logical revisionism, and eventually motivate, from anti-exceptionalist grounds, our preference for one of them. We will start in Ch. 1 by illustrating the anti-exceptionalist methodological framework assumed in this work. Subsequently, in Ch. 2, we will discuss four classically valid principles inadequate to the data of de re intentionality, reject possible attempts, by proponents of so-called realist abstractionist theories of fiction, to deny those data, and present the system P of positive free logic. We will then go on, in Ch. 3, to illustrate the noneist programme of logical revision and a system, N^R, implementing its principles. We will thus argue from anti-exceptionalist grounds that rational theory choice is exercised by choosing N^R. The rest of the chapter is dedicated to defend a realist account about the ontological dependency of the non-existent on the existent. Ch. 4 and Ch. 5 are dedicated to refute attempts, by Timothy Williamson, to reduce disagreements about non-existent objects to cases of merely verbal disagreements. In Ch. 4, we take issue with arguments to the extent that logical disputes about `exists' are genuine only if the parties use it in deductively ways. In Ch. 5 we address his scepticism towards the dispute, about merely possible objects, between actualism and possibilism, and find it unwarranted.
Thesis, PhD Doctor of Philosophy
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