SUBMITTED BY: JOSEPH P. SANOPAO
The theory of the Ideas is the base of Plato’s philosophy: the Ideas are not only the real objects
ontologically speaking, but they are the authentically objects of knowledge epistemologically
speaking. From the point of view of ethics and politics, they are the foundation of the right
behaviour, and anthropologically speaking they are the base of Plato’s dualism and they even
allow him demonstrate the immortality of the soul.
Plato defends a clear ontological dualism in which there are two types of realities or worlds:
the sensible world and the intelligible world or, as he calls it, the world of the Ideas. The Sensible
World is the world of individual realities, and so is multiple and constantly changing, is the world
of generation and destruction; is the realm of the sensible, material, temporal and space things.
On the contrary, the Intelligible World is the world of the universal, eternal and invisible realities
called Ideas (or "Forms"), which are immutable and do not change because they are not
material, temporal or space. Ideas can be understood and known; they are the authentic reality.
The Ideas are hierarchically ordered; there are different types and they do not have all the
same value. The coherency of the arguments Plato uses for defending the existence of the Ideas
would have lead him to claim there are Ideas of all those general words of which we can find an
example in the sensible world, that is to say, of all the universal terms such as "justice",
"rightness" or "man", but also terms as "table", "hair" or "mud". In spite of it, the population of
Ideas postulated by Plato is limited enough by value considerations. Sorts of Ideas that are
included in the intelligible world: the Idea of Rightness and other moral Ideas (Justice, Virtue,
etc.); Aesthetic Ideas (specially the Idea of Beauty), Ideas of Multiplicity, Unity, Identity,
Difference, Being, Not being, mathematical Ideas and other Ideas (the Idea of Man, etc.). Plato
locates the Idea of Rightness on the highest position of that intelligible world; sometimes he
identifies it with the Idea of Beauty and even with the idea of God. The Idea of Rightness is the
origin of the existence of everything because human behaviour depends on it and everything
tends to it (intrinsic purpose in the nature).
I. Plato’s arguments in favour of the Theory of the Ideas
In essence, this theory defends there are certain independent, universal, immutable and
absolute beings which are different from the sensible world.
a) Critic of the sensible knowledge in the dialogue "Theaetetus": Plato shows evidence does not
rise from sensible knowledge. This kind of knowledge leads to relativism, which is, in essence,
absurd (critic of sophist philosophy). Besides, we have knowledge not based on the senses.
Conclusion: science (knowledge strictly talking) based on sensation as criterion for truth is not
possible, because we cannot have science of changeable things (of the sensible world) which
just appears to our senses. Science has to be based on reason, which studies the nature or
essence of things ("Ideas").
b) The use of the language and the problem of the reference of the universal terms. Linguistic
terms as nouns ("table"), adjectives ("good") and abstract nouns ("beauty") of which many
examples can be shown lead to think about the existence of beings different from the individual
and sensible ones. The objects to which names (such as "Socrates" or "Napoleon") refer are
individuals; but we have certain problems about the objects to which other terms (nouns,
abstract adjectives and abstract nouns) refer. We call them UNIVERSAL terms because they do
refer to a plurality of objects. For that reason Plato deduces there must be universal beings
matching up those universal concepts of which there are plenty of individuals or examples; “The
Green” would match the concept of "green", “The Kindness” would match the concept of
"kindness", “The Beauty” would match the concept of "beautiful", “The Truth” would match the
concept of "truth". Those beings which match universal concepts are called Ideas or Forms.
II. THE MYTH OF THE CAVERN, COMPENDIUM OF PLATO’S PHILOSOPHY
In the VII book of the "Republic" Plato displays his well-known myth of the cavern, the most
important one as it embraces the cardinal points of his philosophy. He wants it to be a metaphor
"of our nature regarding its education and its lack of education", that is, serves to illustrate
issues regarding the theory of knowledge. Nevertheless, he clearly knows this myth has
important consequences for other fields of philosophy as ontology, anthropology and even
policy and ethics; some philosophers have seen even religious implications. The myth describes
our situation regarding knowledge: we are like the prisoners of a cavern who only see the
shades of the objects and so live in complete ignorance worrying about what is offered to our
senses. Only philosophy can release us and allow us come out of the cavern to the true world or
World of the Ideas.
Plato requests us to imagine we are prisoners in an underground cavern. We are chained
and immobilized since childhood in such a way we can only see the far end wall of the cavern.
Behind us and elevated there is a fire that lights the cavern; between the fire and the prisoners
there is a path on which edge there is another wall. This second wall is like a screen used in a
puppet theatre; puppets are raised over it to be shown to the public. People walk along the path
speaking and carrying sculptures that represent different objects (animals, trees, artificial
objects...). Since there is this second wall between the prisoners and the people walking, we
only see the shades of the objects they carry projected on the far end wall of the cavern.
Naturally, the prisoners would think the shades and the echoes of the voices they hear are true
Plato argues a liberated prisoner would slowly discover different levels of authentic reality:
first he would see the objects and the light inside the cavern, later he would come out of it and
see first the shades of the objects, then the reflections of those objects on the water and finally
the real objects. At last he would see the Sun and conclude it is the reason of the seasons, it
rules the realm of visible objects and is the reason of everything the prisoners see. And
remembering his life in the cavern, remembering what he thought he knew there and his
captivity comrades he would feel happy for being free and would feel sorry them; prisoner’s life
would seem unbearable for him. But in spite of it and in spite of the dangers, his clumsiness and
the prisoner’s laughs and scorns, he would return to the underground world to free them.
These are the keys Plato gives us to read the myth: we should compare the shadows of the
cavern with the sensible world and the light of the fire with the power of the Sun. The escape to
the outer world to contemplate real beings (metaphor of the World of the Ideas) should be
compared with the path our souls take towards the intelligible world. Plato declares the most
difficult and the last object we reach is the Idea of Rightness (symbolized by the metaphor of the
Sun, the last object the released prisoner sees), which is the reason of all the good and beautiful
things of the world; it is also the reason of the light and the Sun in the sensible and visible world
and the reason of truth and understanding in the intelligible world; is the reality we need see to
live with wisdom.
III. THE THEORY OF THE IDEAS AND PLATO’S EPISTEMOLOGY
The theory of the Ideas answers the question about the possibility of knowledge strictly
talking. This theory divides the world in two realms of reality completely different ontologically
speaking which will match two different wisdoms. Types of knowledge: SCIENCE; which take
care of the immutable Ideas and is divided in dialectic and discursive thought and OPINION;
which is the knowledge of the sensible and changeable world and is divided in belief (which
occupies on the "animals surrounding us, plants and the whole of artificial objects) and
conjectures (which occupies on "shades" and similar things).
Plato distinguishes between discursive thought and dialectic in what he calls SCIENCE. The
first one is mainly identified with mathematics (geometry and arithmetic), and in spite of its
extraordinary value, it has two important deficiencies: it uses sensible symbols and leans on
hypothesis (careful; "hypothesis" in Plato’s philosophy does not mean the same as for us):
mathematicians do not reflect on the being of the objects they deal with (the numbers, for
example) nor settle down any thesis ontologically speaking, and that’s why this science is
incomplete. Dialectic is a superior knowledge, studies the World of the Ideas, that is to say, the
immutable, universal and eternal being, and is identified with philosophy.
Plato, The Republic, tr. by G. M. Grube (Hackett, 1992)