or form from the substance of truth; and both of them had to be
content with an abstraction of science which was not yet realized.
He was the greatest metaphysical genius whom the world has seen;
and in him, more than in any other ancient thinker, the germs of future
knowledge are contained. The sciences of logic and psychology,
which have supplied so many instruments of thought to after-ages, are based
upon the analyses of Socrates and Plato. The principles of definition,
the law of contradiction, the fallacy of arguing in a circle,
the distinction between the essence and accidents of a thing or notion,
between means and ends, between causes and conditions; also the division
of the mind into the rational, concupiscent, and irascible elements,
or of pleasures and desires into necessary and unnecessary--
these and other great forms of thought are all of them to be found
in the Republic, and were probably first invented by Plato.
The greatest of all logical truths, and the one of which writers
on philosophy are most apt to lose sight, the difference between
words and things, has been most strenuously insisted on by him,
although he has not always avoided the confusion of them in his
own writings. But he does not bind up truth in logical formulae,--
logic is still veiled in metaphysics; and the science which he
imagines to "contemplate all truth and all existence" is very unlike
the doctrine of the syllogism which Aristotle claims to have
discovered.

Neither must we forget that the Republic is but the third part
of a still larger design which was to have included an ideal
history of Athens, as well as a political and physical philosophy.
The fragment of the Critias has given birth to a world-famous fiction,
second only in importance to the tale of Troy and the legend of Arthur;
and is said as a fact to have inspired some of the early navigators