The Timpson Lyceum · History of Philosophy (2024)

Plato's Metaphysics and Life – Lecture 17 (History of Philosophy)

Overview

Plato (427–347 BC), born Aristocles and nicknamed "Plato" ("broad") by his wrestling coach, was the aristocratic pupil who immortalized Socrates and built the first complete system of philosophy. Four bruising encounters with politics — the brutality of the Thirty Tyrants (several of them his own kin), the democracy's execution of Socrates, and two failed attempts to school the tyrants of Syracuse — drove him from public life into philosophy. He founded the Academy (c. 387 BC), the first institution of higher learning, whose name gives us "academic" and "academia," and over whose door reportedly stood "Let none ignorant of geometry enter here."

Where Socrates only insisted that the good, the true, and the beautiful are objective, Plato set out to vindicate that conviction with a coherent metaphysics, epistemology, ethics, politics, and aesthetics. His central doctrine is the Theory of Forms: two worlds, a changing world of sensible particulars and an eternal, non-physical world of universals (Forms). Knowledge is of the Forms alone; the sensible world yields mere opinion. Plato reconciles Parmenides (unchanging Being, secured in the Forms) with Heraclitus (flux, confined to particulars) while answering the Sophists' skepticism. Yet he was his own harshest critic — in the Parmenides he tears his own theory apart with the regress argument later known as the Third Man.

Key Concepts

• The five branches — Plato is the first to give a complete, integrated system: metaphysics (what fundamentally exists), epistemology (what and how we can know), ethics (how the individual should live), politics (how the state should be ordered), and aesthetics (the nature of beauty) — all resting on the good, the true, and the beautiful.
• Two worlds — A world of Forms (universals: eternal, unchanging, non-physical, one of each, known by reason) and a world of particulars (this universe: many, changing, physical, temporal, known by the senses). "Chair-ness" exists in the former; individual chairs in the latter.
• Forms, not "ideas" — Plato's Greek word is often rendered idea, but "Form" is preferred so as not to suggest a mere subjective mental content; Forms are real entities existing independently of any mind and of this universe.
• Two founding premises — (1) All knowledge is of what really exists (a Parmenidean point: one cannot know what is not); (2) universals must be knowable, since all knowledge and every definition is framed in universals. Together they force universals to exist somewhere real.
• Argument from opposed properties — Universals cannot be parts of particulars because the two have contrary properties (one vs. many, at rest vs. changing, abstract vs. physical, known by reason vs. by sense); having opposed properties, they must be distinct kinds of things in distinct worlds.
• Argument from perfection — We possess concepts of perfect equality, the perfect triangle, and the like, yet no sensible thing is ever perfect (all change, none is exact). Since knowledge is of what exists, these perfections must exist — in the world of Forms.
• Priority of universals (recollection) — One cannot abstract a universal from particulars without already knowing which particulars to gather; so the universal must come first. The soul knew the Forms before birth; sensation merely prompts recollection (anamnesis), implying innate ideas and the soul's independence from the body.
• Answering Parmenides, Heraclitus, and the Sophists — Knowledge needs unchanging objects (Parmenides), change breeds contradiction and so bars knowledge (Heraclitus), and the senses deceive (Sophists). Plato assigns changeless Forms to reason and knowledge, and the changing sensible flux to mere opinion — satisfying all three.
• Which world is "more real" — By every ordinary sense of "real" (non-contradictory, knowable, more perfect, the original vs. its imitations) the Forms outrank particulars; the sensible world is a shadow or projection of true reality.
• The Timaeus and the Demiurge — In this Pythagorean-flavored dialogue a divine Demiurge ("craftsman"), looking to the Forms, orders pre-existing matter and the void into imitations of the Forms — an early argument from design. Both the Forms and the void are eternal; the world is a projection of the Forms into the 3-D void, which is why particulars are three-dimensional and can change.
• Evil as privation — Forms are good; a thing is good insofar as it imitates its Form. Evil is not a positive thing but a lack of the good, as darkness is merely the absence of light.
• The Form of the Good — The one supreme Form from which all others are ultimately derivable: the source of all existence (everything aims at some good) and of all intelligibility. As the sun both sustains life on Earth and lets us see it, the Good both causes what exists and makes knowledge possible. It is grasped only through dialectic, not written proof — "to those who know, no explanation is necessary; to those who do not, none is possible."
• Teleology vs. mechanism — Plato is a universal teleologist: the cosmos serves a purpose. This answers the "why" that the atomists' mechanism (mere matter in motion) can never supply — the very deficiency that first turned Socrates from natural philosophy.

Worked Example

The Third Man Argument as an infinite regress. Plato's own critique of the Forms (in the Parmenides) shows that three natural assumptions about how a Form relates to its instances generate an unending ladder of Forms. Let $\mathbf{F}$ be a property (say, largeness) and write $F_1$ for the first Form of $F$.

State the three premises:

• (OM) One-Over-Many: whenever many things share a property $F$, there is a single Form of $F$ in virtue of which they are all $F$.
• (SP) Self-Predication: the Form of $F$ is itself $F$ (the Form of Largeness is itself large).
• (NI) Non-Identity: a Form of $F$ is not identical to the things that are $F$ by participating in it (nothing is $F$ by itself).

The regress unrolls:

1. Start with a plurality of large sensible things $\{a, b, c, \dots\}$, each large. By (OM) there is one Form, $F_1$, in virtue of which they are all large.
2. By (SP), that Form $F_1$ is itself large. So now consider the new collection $\{a, b, c, \dots, F_1\}$ — every member is large.
3. This is again a plurality sharing largeness, so (OM) applies once more and posits a further Form, $F_2$, over all of them (including $F_1$).
4. By (NI), $F_2 \neq F_1$, since $F_1$ is one of the large things falling under $F_2$, and no Form is identical to the things that participate in it. Thus $F_2$ is a genuinely new, second Form of largeness.
5. But by (SP) again, $F_2$ is itself large; adjoin it to the collection and (OM) yields $F_3$, with $F_3 \neq F_2 \neq F_1$ by (NI) — and so on without end:

$F_1,\; F_2,\; F_3,\; \dots,\; F_n,\; F_{n+1},\; \dots$

1. At each stage the same three premises regenerate a strictly new Form:

$\underbrace{\{a,b,c,\dots\}}_{\text{all }F}\ \xrightarrow{\text{(OM)}}\ F_1 \ \xrightarrow{\text{(SP)}}\ F_1 \text{ is } F \ \xrightarrow{\text{(OM)}}\ F_2 \ \xrightarrow{\text{(SP)}}\ F_2 \text{ is } F \ \xrightarrow{\text{(OM)}}\ F_3 \ \longrightarrow\ \cdots$

1. The series never terminates, so there is not one Form of $F$ but infinitely many — contradicting (OM)'s promise of a single Form "over the many." The trio (OM), (SP), (NI) is therefore inconsistent: at least one must be surrendered. $\blacksquare$

The argument does not by itself refute the Forms, but it exposes a real tension in how participation and self-predication were conceived — exactly the kind of self-criticism for which Plato preferred the living dialectic to any fixed written doctrine.

Summary

• Plato (427–347 BC), disillusioned with Athenian politics, founded the Academy and built the first complete philosophical system to vindicate Socrates' conviction that the good, the true, and the beautiful are objective and absolute.
• The Theory of Forms posits two worlds: eternal, unchanging universals known by reason, and changing sensible particulars known by the senses — the latter mere shadows of the former, yielding only opinion.
• Four arguments support the Forms — from opposed properties, from perfection, from the priority of universals (recollection), and from the preconditions of knowledge — reconciling Parmenides and Heraclitus while defeating Sophistic skepticism.
• In the Timaeus, the Demiurge orders the void into imitations of the Forms; the Form of the Good is the supreme Form, the source of all being and intelligibility, grasped only through dialectic.
• Plato criticized his own theory with the Third Man regress, showing that One-Over-Many, Self-Predication, and Non-Identity cannot all hold — a hallmark of his relentless, dialectical honesty.