  Plato’s Parmenides consists in a critical examination of the theory of forms, a set of metaphysical and epistemological doctrines articulated and defended by the character Socrates in the dialogues of Plato’s middle period (principally Phaedo, Republic II–X, Symposium). According to this theory, there is a single, eternal, unchanging, indivisible, and non-sensible form corresponding to every predicate or property. The theoretical function of these forms is to explain why things (particularly, sensible things) have the properties they do. Thus, it is by virtue of being in some way related to (i.e., by participating in, or partaking of) the form of beauty that beautiful things (other than beauty) are beautiful, it is by virtue of partaking of the form of largeness that large things are large, and so on. Fundamental to this theory is the claim that forms are separate from (at least in the sense of being not identical to) the things that partake of them.