mission than that of Homer, great as his was, though not so successful.

Parmenides of Elea, born about the year 530 B.C., followed out the
system of Xenophanes, the central idea of which was the existence of
God. With Parmenides the main thought was the notion of _being_. Being
is uncreated and unchangeable; the fulness of all being is _thought_;
the _All_ is thought and intelligence. He maintained the uncertainty of
knowledge, meaning the knowledge derived through the senses. He did not
deny the certainty of reason. He was the first who drew a distinction
between knowledge obtained by the senses and that obtained through the
reason; and thus he anticipated the doctrine of innate ideas. From the
uncertainty of knowledge derived through the senses, he deduced the
twofold system of true and apparent knowledge.

Zeno of Elea, the friend and pupil of Parmenides, born 500 B.C.,
brought nothing new to the system, but invented _Dialectics_, the art of
disputation,--that department of logic which afterward became so
powerful in the hands of Plato and Aristotle, and so generally admired
among the schoolmen. It seeks to establish truth by refuting error
through the _reductio ad absurdum_. While Parmenides sought to establish
the doctrine of the _One_, Zeno proved the non-existence of the _Many_.
He did not deny existences, but denied that appearances were real
existences. It was the mission of Zeno to establish the doctrines of his
master. But in order to convince his listeners, he was obliged to use a
new method of argument. So he carried on his argumentation by question
and answer, and was therefore the first who used dialogue, which he
called dialectics, as a medium of philosophical communication.

Empedocles, born 444 B.C., like others of the Eleatics, complained of
the imperfection of the senses, and looked for truth only in reason. He