The epistemology of modality

[Extract] In this article the term ‘modality’, when unmodified, will refer to metaphysical modality. Metaphysical modality is what is expressed by ‘possible’ and variants such as ‘possibly’, as well as ‘it could have been the case that…’ and variants, when these are used in the broadest objective sense. (Metaphysical necessity is the dual of metaphysical possibility, i.e. it is metaphysically necessary that p iff it is not metaphysically possible that it is not the case that p.) Perhaps the most straightforward way to characterize objective modality is negatively: it is what the modal words express when they are not used in any epistemic or deontic sense (a more precise characterization would take us too far afield).1 Metaphysical modality is what these words express when they express objective modality and are not understood as restricted in any way. For example, ‘Trump could not have won California’ is true on various restricted objective readings, but in the completely unrestricted objective sense it could have been the case that Trump won California. In this sense, Trump could also have orbited Neptune, bicycled from Midtown Manhattan to Teotihuacán in one day, owned 17 talking donkeys, and had ever so many other extremely improbable achievements to his name; but he could not have been Hillary Clinton or any other individual actually distinct from Trump (although he could have looked, sounded, smelled, etc., exactly like Hillary Clinton and many others). The epistemology of modality inquires into the circumstances in which we can obtain knowledge that something is possibly so or necessarily so, in this sense.