Trope theory

Trope theory is the metaphysical view that properties are not universals shared by many particulars, but are instead individualized entities — 'particularized properties' or 'tropes' — that belong to exactly one object. The redness of this apple is not the same redness as the redness of that apple; each has its own distinct trope of redness. Trope theory attempts to split the difference between nominalism (which denies properties as objects) and realism about universals (which posits shared abstract entities). By making properties particular rather than universal, the trope theorist hopes to preserve ontological economy while accounting for resemblance and predication. The position is associated with D.C. Williams and Keith Campbell, and remains a live alternative in contemporary metaphysics.