Modal Branching Temporalism : An Alternative to Lewisian Genuine Realism

Abstract

Possible worlds theory has been wildly successful in contemporary logic and metaphysics ever since Kripke (1959) proved the completeness and consistency of modal logic using possible worlds semantics. According to possible worlds semantics, a proposition P is possibly true if and only if P is true in some possible world and necessarily true if and only if P is true in every possible world. Possible worlds semantics have led to great strides in modal logic. However, possible worlds semantics leaves open the metaphysical question of what exactly possible worlds are. In the last 50 years numerous metaphysical theories have been proposed to explain the nature of possible worlds. Of the theories of possible worlds that have been proposed to date, I believe Lewis’ (1986) Genuine Modal Realism (Genuine Realism for short) is the most plausible because of its incredible explanatory power combined with the compelling arguments he offers against other theories of possible worlds. Despite the benefits, there are significant costs associated with Genuine Realism and due to these costs, I believe there is a better theory of modality available. The goal of this project is to introduce my own theory of possible worlds, called Modal Branching Temporalism, and compare the costs and benefits of it with those of Genuine Realism with the goal of showing that Modal Branching Temporalism is preferable to Genuine Realism. It is worth noting that the goal of this project is not to argue that Modal Branching Temporalism is the most plausible theory of modality or even the most plausible theory of possible worlds. Instead, in this paper I am specifically arguing that it is more plausible than Genuine Realism and leave these further claims for future work. This means that my discussion focuses mainly on Genuine Realism and other theories of modality/possible worlds are only brought in when they are important for understanding either Genuine Realism or Modal Branching Temporalism.