A chance for possibility : an investigation into the grounds of modality

• Main Author: Steinberg, A. T.
• Published: University College London (University of London) 2011
• Subjects: 100
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.625585

The thesis defends the view that the (non-epistemic) modal realm is tripartite: truths about possible worlds supervene on modal truths, which in turn supervene on truths about objective chances. An understanding of supervenience is developed which—unlike the standard understanding of supervenience as a purely modal notion—allows the question of what modal truths supervene on to have a non-trivial answer. Relying on this understanding, a negative result is established: modal truths do not supervene on truths about possible worlds, whether possible worlds are conceived of as Lewisian mereological sums of concrete individuals or as abstract objects of some kind. Instead, a conception of abstract possible worlds is developed and defended according to which the direction of supervenience is the reverse. This leaves the question of whether modal truths themselves supervene on still more basic truths. It is argued that it should be answered in the affirmative. Our use of natural language ‘might’ and ‘might have’ sentences—of those sentences with which we express non-epistemic possibility before we enter the philosophy classroom—provide evidence that modal truths supervene on truths about objective chances.