The Republic is the centre around which the other Dialogues may be grouped; here philosophy reaches the highest point (cp, especially in Books V, VI, VII) to which ancient thinkers ever attained.

Plato among the Greeks, like Bacon among the moderns, was the first who conceived a method of knowledge, although neither of them always distinguished the bare outline 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 (cp.