great importance to a word or idea. The philosophy of the ancients was
still more in slavery to them, because they had not the experience of
error, which would have placed them above the illusion.

The method of the Parmenides may be compared with the process of purgation,
which Bacon sought to introduce into philosophy. Plato is warning us
against two sorts of 'Idols of the Den': first, his own Ideas, which he
himself having created is unable to connect in any way with the external
world; secondly, against two idols in particular, 'Unity' and 'Being,'
which had grown up in the pre-Socratic philosophy, and were still standing
in the way of all progress and development of thought. He does not say
with Bacon, 'Let us make truth by experiment,' or 'From these vague and
inexact notions let us turn to facts.' The time has not yet arrived for a
purely inductive philosophy. The instruments of thought must first be
forged, that they may be used hereafter by modern inquirers. How, while
mankind were disputing about universals, could they classify phenomena?
How could they investigate causes, when they had not as yet learned to
distinguish between a cause and an end? How could they make any progress
in the sciences without first arranging them? These are the deficiencies
which Plato is seeking to supply in an age when knowledge was a shadow of a
name only. In the earlier dialogues the Socratic conception of universals
is illustrated by his genius; in the Phaedrus the nature of division is
explained; in the Republic the law of contradiction and the unity of
knowledge are asserted; in the later dialogues he is constantly engaged
both with the theory and practice of classification. These were the 'new
weapons,' as he terms them in the Philebus, which he was preparing for the
use of some who, in after ages, would be found ready enough to disown their
obligations to the great master, or rather, perhaps, would be incapable of
understanding them.