Date of Award

August 2018

Degree Type


Degree Name

Doctor of Philosophy (PhD)




Mark Heller


Composition, Mental causation, mereological nihilism, Ontology, simples, Truthmaking

Subject Categories

Arts and Humanities


Scientists and metaphysicians alike often accept that the best theory is that which best exhibits familiar theoretical virtues such as empirical testability, fruitfulness, conservatism, explanatory power, and parsimony. In this dissertation, I assume this naturalistically respectable methodology and explore whether it can help decide between competing metaphysical theories. I argue it can.

In chapter 1, I present my version of mereological nihilism, Minimal Truthmaker Nihilism (MTN). According to MTN, only the minimal truthmakers for all true sentences are included in the correct ontology and composite objects are not among the minimal truthmakers. I argue that the proponent of MTN can claim ‘hands exist’ is true, even though hands don’t really exist. In chapter 2, I argue we can use the theoretical virtues to answer the Special Composition question (SCQ), which asks what the necessary and jointly sufficient conditions are under which two or more objects come together to compose a further object. The first four virtues don’t give us any reason to prefer one theory of composition over another. But, I argue, on any plausible understanding of parsimony we have reason to prefer MTN, according to which two or more objects never really compose a further object. Suppose I’m right about that. It’s metaphysical orthodoxy that true metaphysical theories, such as MTN, are necessarily true. Against this orthodoxy -- using the same commonly accepted methodology -- I show that MTN is contingently true.

In chapter 3, I argue for what I’ll call the ‘Nomological Account of Objecthood’ or ‘NAO’ for short. If I’m right, NAO gives us answers to the SCQ and the Simple Question, which asks what the necessary and jointly sufficient conditions are for being a simple. I argue that if we assume the aforementioned methodology and that simples are possibly extended, then NAO is the best theory of objecthood.

In chapter 4, I show how we can put Minimal Truthmaker Nihilism (MTN), to work for us. There is a long-standing problem of how it is that mental properties can cause physical events given that it is widely accepted in the scientific community that every physical event has a sufficient completely physical cause. MTN solves this problem by explaining how microphysical properties and objects located in space-time alone can serve as truth-makers for sentences about the causality of mental properties just as, I argue, microphysical properties and objects can serve as truth-makers for sentences about composite objects such as tables.

Each chapter in the dissertation is written as a stand-alone paper.


Open Access