We represent some things as countable, others only as measurable: for example, while it is standard practice in English to speak of, say, one chair, two trees, many people and few houses, we commonly speak only of some mud, little air, and much sand; hair(s) and chicken(s), interestingly, are conceptualized in both ways. This linguistic distinction, known as the “mass/count-distinction”, is found in an astonishingly wide range of languages. Awareness of it, in the Western tradition, may date as far back as the Presocratics, Plato, and Aristotle; in modern times, its first explicit formulation is usually credited to the Danish linguist Otto Jesperson (The Philosophy of Grammar, 1924).
More so perhaps than any other comparable issue, the mass/count-distinction provides fertile soil on which to debate questions concerning our most fundamental semantic notions as well as ontological questions concerning the basic categories of what there is. Arguably the most central and difficult question posed by the mass/count-distinction is how to account for the special features of mass terms within standard approaches to logic, semantics, and ontology; such approaches tend to privilege singular count nouns by presupposing a domain of objects, each of which in principle can be referred to as a or one something-or-other, for some appropriate singular count noun.
The main focus of my research in this area has been to explore strategies by means of which mass terms can be accommodated within our familiar logical, semantic, and ontological apparatus, without forcing either the reduction of our mass-vocabulary to that of count nouns or the introduction of a mysterious category of “non-objects” or “stuff” to serve as the denotations of mass terms. The mass/count-distinction has been an interest of mine since my (unpublished) doctoral dissertation, Talk About Stuffs and Things: The Logic of Mass and Count Nouns (MIT, 1995); it is also the topic of most of my early work, in particular "Isolation and Non-Arbitrary Division: Frege's Two Criteria for Counting" (1997), "The Semantics of Mass-Predicates" (1999) and "Genericity and Logical Form" (1999). I have more recently returned to the mass/count-distinction in connection with "Review of Henry Laycock, Words Without Objects" (2007) as well as "Nouns, Mass and Count" (2006), where I begin to apply some of the results of my subsequent work in metaphysics (see below) to this linguistic phenomenon.
The second area on which my work has focused concerns the more directly metaphysical question: What is an object? Many philosophers today find themselves in the grip of an exceedingly deflationary conception of what it means to be an object, according to which any plurality of objects, no matter how disparate or gerry-mandered, itself composes an object, even if the objects in question fail to exhibit interesting similarities, internal unity, cohesion or causal interaction amongst each other. To illustrate, according to this approach, George W. Bush’s left hand together with the Eiffel tower compose a further object, their sum, aggregate or fusion, which is partially located in the White House and partially located in Paris. The commitment to such initially counterintuitive objects follows from the belief that no principled set of criteria is available by means of which to distinguish the intuitively gerry-mandered objects from the commonsensical ones; some of my work in metaphysics aims to provide a set of principles heretofore not proposed.
To this end, I have developed a more full-blooded neo-Aristotelian approach, according to which objects are structured wholes: it is integral to the existence and identity of an object, on this conception, that its parts exhibit a certain manner of arrangement. For example, in order for there to be an H2O-molecule, the two hydrogen-atoms and one oxygen-atom that compose it must be arranged in the particular manner of chemical bonding, which requires the atoms in question to share electrons. This conception of parthood and composition is discussed in detail in my book, The Structure of Objects (OUP, 2008), which incorporates many of the ideas and the broader perspective tested out in "The Crooked Path from Vagueness to Four-Dimensionalism" (2003), "Constitution and Similarity" (2004), "Almost Indiscernible Objects and the Suspect Strategy" (2005), "On the Substantive Nature of Disagreements in Ontology" (2005), "Towards a Neo-Aristotelian Mereology" (2006), "Aristotle's Mereology and the Status of Form" (2006), as well as "Review of Theodore Sider, Four-Dimensionalism: An Ontology of Persistence and Time" (2003) and "Review of Verity Harte, Plato on Parts and Wholes: The Metaphysics of Structure" (2004).
From the very beginning, my experience in philosophy has been deeply shaped by my classical training in philology and ancient Greek philosophy; this orientation is evident for example in my very first publication, "Four Eighths Hephaistos: Artifacts and Living Things in Aristotle" (1997), and has continued to influence both my teaching and my research, as is visible for example in "Aristotle's Mereology and the Status of Form" (2006) and "Review of Verity Harte, Plato on Parts and Wholes: The Metaphysics of Structure" (2004); moreover, a sizeable chunk of my book, The Structure of Objects (OUP, 2008) is devoted to a detailed discussion of Plato’s and Aristotle’s views on parts and wholes, which I have found to be extremely rich and inspiring. More generally, I advocate a conception of metaphysics that runs counter to some current trends and is in many ways closer to Aristotle’s. It has been the motivating conviction of my approach to metaphysics that the apparatus needed to give an adequate account of such notions as part and whole requires us to re-introduce into our conceptual schemes such philosophically substantive notions as structure and dependence, which are a central component of such systems as Aristotle’s, but tend to fall outside the scope of the more austere logically driven formalisms that dominated contemporary metaphysics for several decades. My more recent work continues in this vein.