Modal realism and acquaintance.
Oladapo, Omoge Michael.
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All propositions intelligible to us, whether or not they primarily concern things only known to us by description, are composed wholly of constituents with which we are acquainted, for a constituent with which we are not acquainted is unintelligible to us. Bertrand Russell, 1910. This thesis explores modal knowledge. Modal knowledge is such that we are often confounded when we are asked to present justifications for it. This is due to (1) the fundamental role acquaintance plays in the formation of knowledge, and (2) the seeming absence of acquaintance with modal facts. Since modal propositions are intelligible to us, then given Russell’s theory, modal propositions are composed wholly of constituents with which we are acquainted despite (2). In this thesis, I argue that we can construct an acquaintance theory for modal facts, and I call such theory ‘modal acquaintance’. Since acquaintance is sufficient as justification for knowledge, then our modal knowledge is justified through modal acquaintance. Chapter 1 introduces modal nihilism and modal scepticism as objections to modal knowledge. It poses the research question, which serves as guide to the analyses and structure of the research and it provides background assumptions. Notable among the assumptions is the adoption of the Lewisian version of modal realism as the theoretical framework of this research. Chapter 2 focuses on the role of acquaintance in knowledge formation and explains that acquaintance could be understood in two senses. The first is the standard Russellian sense and arguably the one absent by default in any function from this world to possible worlds due to its requirement of sense-data as object. The second is not as rigid as the first in that it allows more entities which are internal to the subject to be objects of acquaintance. Among these internal entities, ‘thoughts’ were isolated as the closest identifier of modal facts, precisely because the truth of modal thoughts depends on whether or not they correspond to modal facts. This correspondence allows for the construction of modal acquaintance. Chapter 3 presents accounts of how we have modal knowledge. The presentation begins with Lewis on how we know the contents of his possible worlds. Then, I consider some recent accounts of modal epistemology. The accounts include Yablo and Chalmers in the conceivability camp; Williamson and Hill in the counterfactual camp; and Bealer in the understanding camp. Chapter 4 explains why acquaintance provides a straightforward way to justifying modal knowledge. Since Lewis urges us to take more seriously the metaphysics of modality than its epistemology, attention shifted to the recent account of modal epistemology. The recent accounts were incorporated into the Lewisian modal realism before identifying which among them contains an account of modal justification. They were all found wanting, hence, modal acquaintance was put forward as a better alternative. The theory of ‘threshold’ was developed as a cross-world apparatus to enable modal acquaintance to achieve its justification task.