Metaphysics and categories

Aristotle famously described metaphysics as ‘First Philosophy’ or ‘first science’. In a similar vein, E. J. Lowe has described metaphysics as ‘the systematic study of the most fundamental structure of reality’ (1998: 2). As such, metaphysics examines the more general categories of being, and the more general ways in which entities are related to one another. Accordingly, metaphysics includes ontology, the science of being, concerned with the categorization of what exists, and cosmology, the science of reality as an orderly whole, concerned with characterization of reality as an ordered law-governed system. It should be noted that these ontological and cosmological enterprises are intertwined with one another.

In one very broad sense of ‘category’, any predicate which denotes a non-empty class, or which (holding its actual meaning constant) could or might denote such a class, expresses a category. In this weak sense of ‘kind’ or ‘category’, predicates such as ‘sweet’, ‘red sock’, ‘horned horse’, ‘cube’, ‘table’, ‘cat’, ‘cat or eagle’, and ‘substance or event’ express categories. However, in a much narrower sense only categories of being or ontological categories qualify as ‘categories’. Aristotle was likely the first to explicitly acknowledge the centrality of categories in this sense to metaphysics. Examples of such categories are substance (and more specifically body and soul), event, time, place, absence, boundary, property, relation, proposition, set, and number. Categories of this kind are, or at least purport to be, highly general, or more basic, kinds of being.