MoL-2018-18: The Problem of Counterpossibles

MoL-2018-18: Viterbo Ferreira, Jorge (2018) The Problem of Counterpossibles. [Report]

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The standard semantics for counterfactuals, due to Lewis (1973) and Stalnaker (1968), defends that a counterfactual p ⇒ q is true if, and only if, q is true at all the closest possible worlds where p is true. This semantics predicts that all counterfactuals with metaphysically impossible antecedents are vacuously true. This goes against our linguistic intuition - some counterfactuals with metaphysically impossible antecedents seem false. This is a problem for the standard semantics - the problem of counterpossibles.
Those that think we should accept that all counterpossibles are vacuously true are called vacuists and their opponents are called non-vacuists. Some non-vacuist semantics have been proposed, most notably by Nolan (1997) and Berto, French, Priest and Ripley (2017). These semantics keep the general structure of the standard semantics intact but add impossible worlds - points of evaluation where impossible propositions can be true. The vacuists, most notably Williamson (2017), claim that this cure is worse than the disease.
In this thesis I will try to do three things. 1- Clarify the terms of the debate between vacuists and non-vacuists; 2- Point out where I think the existing literature is mistaken; 3- Develop a moderate form of non-vacuism (also defended by Kment 2014) which will help highlight what the minimal theoretical commitments of non-vacuism are.
The structure of the thesis is as follows. Chapter 1 introduces the problem of counterpossibles in detail, sketches the general vacuist strategy and discusses the methodological assumptions implicit in the debate. The vacuist accuses the non-vacuist of being committed to a number of theoretical costs that offset the benefits of fully respecting our linguistic intuition. The rest of the chapters each deal with one of these costs. Chapter 2 deals with the use of impossible worlds in semantic theorizing. Chapter 3 discusses the accusation that the non-vacuist must have an objectionably weak counterfactual logic. Chapter 4 is concerned with the effects of accepting non-vacuism for our epistemology and understanding of metaphysical modality. Chapter 5 deals with the question of whether non-vacuism is committed to the failure of the substitutivity of identicals in the scope of counterfactuals and whether this is a problem. Chapter 6 concludes.

Item Type: Report
Report Nr: MoL-2018-18
Series Name: Master of Logic Thesis (MoL) Series
Year: 2018
Subjects: Logic
Depositing User: Dr Marco Vervoort
Date Deposited: 27 Sep 2018 16:02
Last Modified: 27 Sep 2018 16:02

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