THE PHILOSOPHY OF
PLATO
Plato was born into a wealthy family in the last days of the Athenian Empire. When the Peloponnesian war ended in 405 he was in his early twenties, just old enough to have fought in it, as his brothers certainly did. His uncles, Critias and Charmides, were two of the Thirty Tyrants.
Socrates’ execution in 399 under a restored democracy gave Plato a lifelong distrust of demagogues, and a distaste for a political career in Athens. ((Anthony Kenny An Illustrated Brief History of Western
Phılosophy, Blackwell Publishing 2006 p.37.)
about Ideas and their relations to ordinary things in the world.
(1) Wherever several things are F, this is because they participate or imitate a single Idea of F.
(2) No Idea is a participant or imitator of itself.
(3) (a) The Idea of F is F. (b) The Idea of F is nothing but F.
(4) Nothing but the Idea of F is really and truly altogether F.
(5) Ideas are not in space or time, they have no parts and do not change, they are not perceptible to the senses. ((Anthony Kenny An
Illustrated Brief History of Western Phılosophy, Blackwell Publishing 2006
p.41.)
Theses (1), (2) and (3) make up an inconsistent triad. The difficulty to which they lead was first expounded by Plato himself in the Parmenides.
Let us suppose we have a number of individuals each of which is F.
Then, by (1), there is an Idea of F. This, by (3), is itself F. But now the Idea of F and the original F things make up a new collection of F things.
By (1) again, this must be because they participate in an Idea of F. But, by (2), this cannot be the Idea first postulated. So there must be another Idea of F; but this in its turn, by (3), will be F; and so on ad infinitum. So, against (1), there will be not a single Idea but infinitely many. ((Anthony Kenny An Illustrated Brief History of Western Phılosophy, Blackwell
Publishing 2006 p.41.)
Plato relied on the Theory of Ideas not only in the area of logic and
metaphysics, but also in the theory of knowledge and in the foundations
of morality. To see the many different uses to which he put it in the years
of his maturity, we cannot do better than to consider in detail his most
famous dialogue, The Republic. (Anthony Kenny An Illustrated Brief
History of Western Phılosophy, Blackwell Publishing 2006 p.44.)
The Republic is concerned more with moral education than with
mathematical education; but it turns out that this follows a parallel path.
Imagination in morals consists of the dicta of poets and tragedians. If the pupil has been educated in the bowdlerized literature recommended by Plato, he will have seen justice triumphing on the stage, and will have
learned that the gods are unchanging, good, and truthful. This he will later see as a symbolic representation of the eternal idea of Good, source of truth and knowledge. The first stage of moral education will make him competent in the human justice which operates in courts of law. This will give him true belief about right and wrong; but it will be the task of dialectic to teach him the real nature of justice and to display its participation in the Idea of the Good at the end of dialectic’s upward path. Every Idea, for Plato, depends hierarchically on the Idea of the Good: for the Idea of X is the
perfect X, and so each Idea participates in the Idea of Perfection or Goodness. In the allegory of the cave, it is the Idea of the Good which corresponds to the all-enlighteningsun(Anthony Kenny An Illustrated Brief History of Western Phılosophy, Blackwell Publishing 2006 p.50.)
