Abstract

Some things happen or exist only contingently: although they do happen or exist, they do not have to. Some other things do not happen or come to exist, although they could. They are contingent possibilities. Philosophers have tried to understand contingent possibilities in two different ways. According to one, possibilities should be understood with reference to worlds. A nonactual event is possible because there is a world in which it does happen. According to another, possibilities should be understood with reference to modal properties. An event or an object is possible because it would occur or come to exist if a modal property of some substance, another object or set of objects were exercised. This book argues that the latter approach provides a better account of possibilities than the former. It develops a theory of contingent possibilities according to which possibilities within a world must be distinguished from the possibility of worlds. It is the distribution of modal properties within a world which metaphysically determines what could happen in that world. The most important of these modal properties are abilities and dispositions. Dispositions explain nomic and behavioural regularities, while abilities ground more or less abstract possibilities. By way of connecting the ascription of more or less specific modal properties to different counterfactual conditionals, we can identify various possibilities that we are concerned with when we try to understand what can happen in our world.