Plato's Theory of Forms and the Parmenides Dialogue

Introduction to Plato's Parmenides and the Theory of Forms

Parmenides is one of Plato's most important dialogues, according to both ancient and modern scholars. It focuses on the critique of the theory of Forms, drawing on the influence of pre-Socratic thinkers such as Pythagoras, Parmenides, and Heraclitus. The theory of Forms is founded on the assumption that a higher, spiritual realm of Forms — or Ideas — exists beyond the world of physical things.

The realm of Forms has a hierarchical order, with the highest level being that of the Form of Good. The physical world, as perceived by the senses, is in constant flux, making knowledge derived from it variable and restricted. The realm of Forms, however, is only apprehensible by the mind and is eternal and changeless. Each Form is a pattern corresponding to a certain category of things in the physical world — things which are only imperfect copies of the perfect Forms.

Although in the Phaedo dialogue Socrates seems to describe the theory of Forms as a very familiar concept that he has applied for a long time without any difficulties, the Parmenides — a dialogue of the second period — contains a set of criticisms of this theory. Scholars have therefore asked whether Plato had two distinct philosophies, an earlier and a later, or whether the main objective of the first dialogues was to preserve the memory of Socrates by presenting his ideas from a Platonic perspective, while the later dialogues contain Plato's own distinctive thought.

Plato's Parmenides has influenced many thinkers of the Western world: Plotinus, Proclus, Dionysius the Areopagite, Nicholas of Cusa, and G. W. F. Hegel. In order to understand how Plato arrived at the conclusions presented in this dialogue, however, an analysis of the work of Parmenides, Pythagoras, and Heraclitus is required.

Heraclitus: Flux, Logos, and the Unity of Opposites

Heraclitus remains famous for his panta rhei doctrine ("all flows"). The flux of all things imagined by Heraclitus is actually the perpetual becoming of life and death, which are unified by this process. The general concept taught by Heraclitus is that there is a dynamic unity of all opposites, and that the main characteristic of this flux of existing things is the constant transformation between pairs of contrary principles. An apparent contrast with the static separation of substantial entities is unavoidable, because the dynamic transformation of opposites into each other seems irreconcilable with a fixed structure. Nevertheless, Heraclitus builds his flux-related ideas on the foundation of the Logos — the supporting structure of both the world and the mind.

He argues that it is not his own arguments but the Logos itself that leads the hearer to acquiesce to the idea that all things are one. Heraclitus held that only the ignorant fail to understand how a thing agrees with itself in differing, and he illustrated this theory by drawing a connection between the bow and the lyre.

The conclusion is that Heraclitus perceived the world as a perpetual transformation of things into their opposites. The rule according to which these transformations are performed is that of the Logos, which can only be expressed in contradictions.