Top-level categories of an ontology are derived from contrasting features that distinguish the entities of a subject domain. Each distinctive feature is associated with axioms that are inherited by every entity or category of entities that have that feature. A hierarchy of categories can then be derived as a lattice formed as a product of the fundamental distinctions. This paper develops such a lattice based on philosophical distinctions taken primarily from the theories of Charles Sanders Peirce and Alfred North Whitehead.