Plato, the person who created the idea of Platonic realism

Platonic realism is the theory of reality developed by Plato, and explained in his theory of forms. Platonic realism states that the visible world of particular things is a shifting exhibition, like shadows cast on a wall by the activities of their corresponding universal Ideas or Forms. Whereas the visible world of particulars is unreal, the Forms occupy the unobservable yet true reality and are real.

Platonism is a similar, yet sometimes modified, view of reality.