Three matchsticks could be arranged on a table so as to form a triangle. Were you to place a lump of sugar into a cup of hot tea it would dissolve. You might never have been born. Such assertions express modal judgements and, as we suppose, truths about the universe. But if modal judgements can be true, what features of the universe make them true? Thanks largely to the efforts of David Lewis, philosophers nowadays find it natural to appeal to (...) alternative worlds to explicate modality. Something is possible if it occurs in at least one alternative world. A subjunctive conditional is true if, in the ‘nearest’ worlds in which its antecedent is true, its consequent is true. This paper includes a discussion of Lewis's ‘Humean’ ontology, the role alternative worlds play in Lewis's account of modality, and an Aristotelian alternative. (shrink)

Here we challenge the orthodoxy according to which abduction is an a posteriori mode of inference. We start by providing a case study illustrating how abduction can justify a philosophical claim not justifiable by empirical evidence alone. While many grant abduction's epistemic value, nearly all assume that abductive justification is a posteriori, on grounds that our belief in abduction's epistemic value depends on empirical evidence about how the world contingently is. Contra this assumption, we argue, first, that our belief in (...) abduction’s epistemic value is not and could not be justified a posteriori, and second, that attention to the roles experience plays in abductive justification supports taking abduction to be an a priori mode of inference. We close by highlighting how our strategy for establishing the a priority of abduction positively contrasts with strategies in Bonjour (1998), Swinburne (2001), and Peacocke (2004) aiming to establish the a priority of certain ampliative modes of inference or abductive principles. (shrink)