Plato

Plato (c. 428 – 348 BCE) was an Athenian of aristocratic birth whose work
gave Western thought many of its enduring questions and much of its
vocabulary. A pupil of Socrates and the teacher of Aristotle, he founded the
Academy on the outskirts of Athens, an institution often described as the
first university of the Western world, where mathematics and dialectic were
pursued for the better part of a millennium.

Plato wrote almost exclusively in dialogue form, casting Socrates as the
principal speaker in most of his works. This choice is itself philosophical:
truth, for Plato, emerges through the friction of conversation rather than
the pronouncement of doctrine. The early dialogues preserve the Socratic
search for definitions and typically end in impasse. The middle dialogues —
the Republic, the Phaedo, the Symposium — develop a positive metaphysics,
while the late works subject his own earlier views to searching criticism.

At the centre of his mature thought lies the theory of Forms. Beyond the
shifting world of the senses, Plato argued, there exists a realm of perfect,
unchanging archetypes — Justice itself, Beauty itself, the Good itself — of
which sensible things are imperfect copies. Knowledge in the strict sense is
of the Forms; what we gather from the senses is mere opinion. The famous
allegory of the cave dramatizes this ascent: prisoners mistaking shadows for
reality until one is dragged into the sunlight of genuine understanding.

The Republic weds this metaphysics to a vision of politics. Justice in the
city mirrors justice in the soul, each consisting in the right ordering of
its parts. Plato's ideal state is governed by philosopher-rulers whose grasp
of the Good fits them to rule — a proposal as provocative now as in
antiquity, and one he himself appears to have qualified in later works such
as the Laws.

Plato's reach is difficult to overstate. The philosopher Alfred North
Whitehead remarked that the European philosophical tradition consists of a
series of footnotes to Plato. Whether one accepts or rejects his doctrines,
the questions he posed — about knowledge, reality, justice, and the good
life — continue to frame the discipline he did so much to define.