Universals

Universals are properties, types, or relations that can be instantiated by more than one particular. They contrast with particulars, which are individual objects or events that bear those properties. A universal such as redness can be exemplified by many red objects, and the same universal can be predicated of each of them. Scholarly discussions of universals address whether these entities truly exist, and if so, in what way.

Historically, the question began with Plato, who held that universals, or Forms, exist independently of the material world as perfect entities. Aristotle rejected separate realms for universals, arguing that universals are real only insofar as they are instantiated in concrete substances; they are real but grounded in the particulars rather than existing as detached entities. In the medieval period, philosophers debated realism, conceptualism, and nominalism. Realists maintained that universals are objective and mind-independent; conceptualists held that universals exist as mental concepts; nominalists denied universal real existence, treating them as mere names or linguistic shortcuts. The rise of modern philosophy brought further positions, including trope theory, which treats particularized properties (trope) as the basic building blocks, and various forms of abstract-object theories that treat universals as abstract entities.

In contemporary metaphysics, the problem of universals persists as the problem of how many distinct universals there are, how they relate to particulars, and whether predication relies on shared properties or linguistic and cognitive practices. The discussion intersects semantics, philosophy of science, and ontology, influencing how scientists classify properties and how language generalizes about the world.