, is thus the fundamental
principle which pervades the whole of the Platonic philosophy. And now,
having attained this sublime elevation, he looks down from thence upon
the _sensible, the phenomenal world_, and upon _the temporal life of
man;_ and in the light of this great principle he attempts to explain
their meaning and purpose. The results he attained in the former case
constitute the Platonic _Physics_, in the latter, the Platonic _Ethics_.

I. PLATONIC PHYSICS.

Firmly believing in the absolute excellence of the Deity, and regarding
the Divine Goodness as the Final Cause of the universe, he pronounces
the physical world to be an _image_ of the perfection of God.
Anaxagoras, no doubt, prepared the way for this theory. Every one who
has read the "Phaedo," will remember the remarkable passage in which
Socrates gives utterance to the disappointment which he had experienced
when expecting from physical science an explanation of the universe.
"When I was young," he said--"it is not to be told how eager I was about
physical inquiries, and curious to know _how the universe came to be as
it is_; and when I heard that Anaxagoras was teaching that all was
arranged by _mind_, I was delighted with the prospect of hearing such a
doctrine unfolded; I thought to myself, if he teaches that mind made
every thing to be as it is, he will explain _how it is_ BEST _for it to
be_, and show that so it is." But Anaxagoras, it appears, lost sight of
this principle, and descended to the explanation of the universe by
material causes. "Great was my hope," says Socrates, "and equally great
my disappointment."[645]

[Footnote 645: "Phaedo," Secs. 105, 106.]

Plato accepted this suggestion of Anaxagoras with all his peculiar
earnestness, and devoted himself to its fuller development. It were a
vain and profitless theory, which, whilst it assumed the existence of a
Supreme Mind, did not represent that mind as operating in the universe
by _design_, and as exhibiting his intelligence, and justice, and
goodness, as well as his power, in every thing. If it be granted that
there is a Supreme Mind, then, argued Plato, he must be regarded as "the
measure of all things," and all things must have been framed according
to a plan or "model" which that mind supplied. Intelligence must be
regarded as having a _purpose_, and as working towards an _end_, for it
is this alone which distinguishes reason from unreason, and mind from
mere unintelligent force.