Moderate Modal Metaphysics

Abstract

This dissertation is about metaphysical modality: What is possibly or necessarily true? And how do these truths get to be true? It is also about a vice of moderate answers to these questions.

Chapter 1 ('Actualism, Modal Reductionism, and Contingentism') concerns how modal truths get to be true. It's metaphysically necessary that I'm human, even at worlds without me. But how do these worlds get to boast of this truth? Chapter 1 provides an answer: All truths of possible worlds owe their truth to actual individuals and how they are. It's true of any possible world that, necessarily, I'm human because, actually, I'm essentially human.

Chapter 2 ('Higher-Order Contingentism and the Problem of Incompossible Indiscernibles') concerns what is possibly or necessarily true. Specifically, it considers whether it's possible that incompossible individuals bear relations to one another. Whether incompossibles can be related matters to higher-order contingentism, the view that it's contingent which properties exist. Take two doppelganger knives that would have been constituted by the same handle, but different blades. According to higher-order contingentism, if neither knife exists, properties that would single either knife out also do not exist. The knives are indiscernible. If it is really true that, possibly, the knives are indiscernible, the higher-order contingentist denies the being constraint, the constraint that, necessarily, only existing individuals exemplify properties. Chapter 2 resolves this tension.

The emerging metaphysical picture is one in which actuality is special. This raises a powerful arbitrariness worry: If actual individuals are the sole determiner of modal truths, and if which individuals actually exist is arbitrary, then which modal truths there are will also be arbitrary.

Chapter 3 ('Tolerating Arbitrariness') explores arbitrariness as a theoretical vice. Arbitrary theories inexplicably distinguish between things "on a par.'' But not all arbitrary theories are, themselves, on a par. Some arbitrary theories have relatively shallow inexplicability, and they ought to be tolerated. By focusing our attention on different levels of explanation, we open the door for arbitrariness in our metaphysics.