Abstract

Recent attempts to understand modality have centered upon possible worlds. One view, offered by David Lewis, is that there are an infinite number of worlds that exist like our own, and that the existence of these worlds makes our modal claims true. This view is widely held to be unbelievable. Other philosophers hold an "actualist" position: the only world which exists is the actual world, and the only objects that exist are those that exist in the actual world. I assume that some form of actualism is correct. Actualists attempting to reconcile actualism with a possible worlds view reject Lewis's conception of a possible world, but keep the basic logical structure that a possible worlds view entails. Such views must deal with a simple problem: she must make claims about the possible existence of objects which do not actually exist, without postulating the existence of possible objects. Actualist accounts to overcome this problem divide into three kinds. The first kind, offered by Plantinga, relies upon the existence of unexemplified essences. These special properties then play the role that individuals play in Lewis's Realism. I argue that one must refer to unactual objects in order to understand what unexemplified essences, and that Plantinga's account relies upon an equivocation of the term "exemplify." The second kind of solution, offered by Adams, uses general properties to pick out the unactual possibilities. I argue that this attempt breaks down when Adams uses quantifiers to understand the general possibility. The third solution, offered by Armstrong, makes possible worlds and modality fictional. But it is difficult to see how we can get truth from fiction. Without an actualist solution to the problem, the actualist cannot use the notion of a possible world. My account uses the scientific notions of systems and states to overcome these problems. A state s of a system is possible just in case there are rules of transformation through which s is obtainable. Possible states are dispositional properties of systems. The structure of states are quite different from possible worlds, and I sketch a logic of states