The Role of Simplicity in Metaphysics

There has been a great deal of debate regarding what methodology we should employ when we are doing metaphysics. One idea is that we should employ some of the same criteria of theory choice we employ in other theoretical contexts, such as science or everyday life. Arguably one such criterion is simplicity. For example, we search for the simplest fundamental physical laws capable of accounting for our observations; we search for the simplest account of the origin of life compatible with everything else we know about the world (e.g., we might prefer a single event of abiogenesis in Earth’s history rather multiple such events, if this is compatible with what else we know about the world); we search for the simplest account of someone’s death compatible with what else we know about the world (e.g., we postulate a single murderer rather than a large conspiracy of murderers, if this is compatible with what else we know about the world). Some metaphysicians have thought that we can employ a simplicity criterion in metaphysics as well.
In this presentation I will describe some uses to which simplicity has been put in metaphysics, including cases which are such that a simplicity criterion would, it seems to me, unambiguously support one metaphysical hypothesis over its rivals. I will also address some objections which have been made to the use of simplicity as a criterion of theory choice in metaphysics, and I argue that these objections are unsuccessful. Finally, I will present a new and surprising application of the criterion of simplicity within metaphysics. I will argue that considerations regarding simplicity may shed some light on why there is something rather than nothing.