Testing the theory of forms › A young Socrates meets an older critic

Suppose you explain several fair decisions by saying that each answers to the same standard of fairness. Someone then asks what connects that standard to the decisions. If they resemble it, why does resemblance explain anything? If the standard itself is fair, must it answer to a further standard? What looked like an explanation has become something that needs explaining.

This is a modern illustration of the pressure Plato puts on the Forms in the Parmenides. The dialogue examines whether a single intelligible reality can explain many things without becoming another unexplained member of the group. It also asks whether separating that reality from ordinary things threatens the possibility of knowing it. These are challenges to particular assumptions about explanation and participation. They do not amount to an automatic refutation of every theory that recognizes shared properties.

The work gives its reader two tasks. First, follow the objections closely enough to see which assumptions produce them. Then consider why Parmenides responds to the difficulty by demanding more dialectical training. The long exercise that follows does not end with a simple announcement that Socrates has either won or lost.

Plato presents the conversation through a chain of narrators: Cephalus reports Antiphon's retelling of an account learned from Pythodorus. Within that narrated scene, Socrates is very young, Parmenides elderly, and Zeno is reading an argument connected with the problems of plurality. These are features of the dialogue's dramatic construction. The text alone does not establish that the conversation occurred as narrated. See Parmenides 126a–128e.

Socrates distinguishes things that possess contrary characteristics from the Forms themselves. A person can be one person and also many parts. Showing that a person is one and many is therefore less surprising to him than showing a corresponding entanglement within unity and plurality themselves. His proposal moves the difficulty from familiar objects to the intelligible objects through which he hopes to explain them (128e–130a).

A Form, for the account being examined, is a reality such as Likeness itself or Justice itself, distinguished from the many things that participate in it. Participation is the proposed relation by which similar things are similar or just things just. Naming that relation does not yet explain how it works. Parmenides begins to test that gap between an explanatory name and an explanatory account (130a–131a).

This distinction of voices matters. Plato wrote the dialogue, but that does not make every statement by Parmenides a settled declaration of Plato's beliefs. Nor should Socrates' difficulty be turned into a story about a documented crisis in Plato's personal life. The text gives us arguments to assess; its dramatic arrangement does not by itself supply a chronology of the author's intellectual development.