How does Plato’s theory of Forms represent a form of realism about universals?

Plato’s theory of Forms represents a foundational doctrine of realism regarding universals because it posits that general properties—such as "the Beautiful" or "the Just"—exist as abstract, eternal, and changeless entities independent of both mental activity and the sensible particulars that instantiate them.12

This perspective is classified as an extreme form of realism, often termed universalia ante rem ("universals before things"). Key aspects of this theory include:12

• Independent Existence: Forms exist "over and above" particular objects. They are not located in space or time and do not require the existence of any particular thing to remain valid; for instance, the Form of a horse would persist even if all horses became extinct.12
• Participation: Sensible particulars are considered less "real" than Forms because they are not ontologically basic. Instead, they "participate" in or fall under these fundamental entities, which serve as the necessary explanation for why general terms apply to multiple distinct objects.32
• Intellectual Access: Because Forms are supersensible, they lie beyond the reach of sense perception. They are knowable only through the philosophically schooled intellect, contrasting with the mere beliefs derived from observing the changing, imperfect sensible realm.12