The Foundations of Modal Metaphysics

This dissertation develops and argues for a new foundation—which I call simple heterodoxy—for modal metaphysics. Simple heterodoxy has three key elements: a view about language, on which we ought to write our modal metaphysics in an extended version of English which I call English*; a view about worlds, according to which worlds are (very roughly) just arbitrary assignments of truth values to the sentences of English*; and a view about truth, according to which a sentence of English* has a truth value according to a world if the assignment maps that truth value to the sentence. And my goal in the dissertation is to show how, across a range of areas in modal metaphysics, simple heterodoxy provides us with distinctively powerful accounts of this or that metaphysically interesting phenomenon. In the first chapter of the dissertation, I spell out simple heterodoxy more precisely; contrast it with the orthodox views about language, truth, and worlds; and sketch the abductive methodology I’ll use in the dissertation. In the second chapter I show how simple heterodoxy lets us give a powerful account of counterfactuals’ truth conditions: an account which both does a better job of aligning with our ordinary views about counterfactuals than others, and which avoids various logical and mathematical objections. In the third chapter I show how simple heterodoxy lets us give a powerful account of grounding: the relation of metaphysical dependence which underpins relations of non-causal explanation. And in the fourth chapter I show how simple heterodoxy lets us improve dispositionalist accounts of possibility: accounts on which sentences are possible just in case something has a certain disposition.