The Theory of Forms
Why do we call many different things beautiful, or equal, or just? Plato's answer is that each name points beyond the things to a single, perfect reality: a Form.
The basic idea
Everything we see changes and falls short. Any two sticks we call equal are only roughly equal; any beautiful face will age. Yet we understand perfect equality and beauty itself well enough to notice the shortfall. Plato concluded that these standards, the Forms, really exist: eternal, unchanging and knowable by thought rather than the senses.
Participation
Physical things are what they are by “participating” in Forms. A beautiful painting is beautiful because it shares, imperfectly, in the Beautiful itself. The Forms are not in space or time; they are the patterns that make the world intelligible.
The Divided Line
In the Republic, Plato divides what can be known into four levels: images and shadows; physical objects; mathematical objects, reached by reasoning from assumptions; and finally the Forms, grasped directly by understanding. At the summit stands the Form of the Good, which Plato compares to the sun. See The Allegory of the Cave.
Why Plato needed the Forms
- Knowledge: real knowledge must be of something stable; the changing world gives only opinion.
- Meaning: general words like “justice” need something general to refer to.
- Ethics: if goodness is real and knowable, moral questions have real answers, which is what Socrates' questioning assumed.
Plato's own doubts
In the Parmenides, Plato lets a young Socrates face sharp objections. Most famous is the “Third Man”: if large things are large by sharing in Largeness, what do large things and Largeness have in common? A further Form, and so on without end. Aristotle pressed this and other objections, arguing that forms exist only in things themselves.
Legacy
The Forms shaped Neoplatonism, medieval theology and debates about universals that continue today. Mathematicians who believe numbers exist independently of minds are often called Platonists for this reason.
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