I have broad interests in metaphysics, but my chief research interests lie in three areas:

Metaphysics. I am interested in a collection of interrelated ontological questions about identity, composition, time, persistence through time, and vagueness. I am also interested in the ontology of abstract objects, the mind/body problem, and the metaphysics of freedom.          

Metaphysical issues in philosophical theology, especially issues about divine agency, such as  theories of providence (e.g., Molinism and its ongoing debate with open theism), divine conservation, and creation (e.g., whether abstracta are created, so that one necessary existent may depend on another).           

The borderland of metaphysics and logic, especially where it overlaps the areas mentioned above. This includes modal and counterfactual logic and the metaphysical questions they raise, such as those about the nature of possible worlds and the grounding of counterfactuals of freedom.          

My current project is Unity and Persons: An Essay in Ontology (working title), a book on the ontology of composition and the ontology of persons. I argue in Part I that one of the extreme theories of composition—either unrestricted composition or mereological nihilism—must be correct, but that there are no compelling arguments that favor one of the two over the other. Given the disjunction of the extreme views, mereological essentialism is a natural step. Mereological extremism and essentialism together provide straightforward identity conditions for material objects: A is identical to B iff A has the same parts as B. Happily, these theses solve or dissolve many of the most worrisome ontological puzzles about material objects. They do, however, have some surprising consequences, such as the view, defended in Part II, that human persons are immaterial objects. Immaterial persons and their transient bodies together form medium-scale ecosystems. These anthroposomatic systems have a high degree of functional unity, but do not have ontological unity, i.e., oneness.