Plato’s Theory of Participation: Platonic Forms and the Making of Sense Objects
It is correct to say, with certain Friends of the Forms, that Plato’s separate Forms (i.e., non-spatial Forms existing independently of their worldly participants) are not perfect or unqualified instances of themselves, as asserted by prominent Foes of the Forms; rather, they are abstract intelligible entities that do not, with a few exceptions, exemplify themselves. However, this does not yet explain how worldly things can possibly “participate” in Forms, or how that participation can make worldly things be what they are. This paper formulates and defends an explanation of “participation”, drawing heavily on the role of the Good as source of the “being and essence” (einai kai ousia, Rep. 509B) of all other Forms, and the related idea that participants in Forms are essentially things (taken broadly to include objects, actions, relationships, et al.) of types that have some necessary role to play, directly or indirectly, in the construction and functioning of an optimal created cosmos.
Patterson, Richard, "Plato's Theory of Participation: Platonic Forms and the Making of Sense Objects" (1980). The Society for Ancient Greek Philosophy Newsletter. 232.