The influence of analogy led him to invent 'parallels and conjugates' and to overlook facts.

To us some of his difficulties are puzzling only from their simplicity: we do not perceive that the answer to them 'is tumbling out at our feet.' To the mind of early thinkers, the conception of not-being was dark and mysterious; they did not see that this terrible apparition which threatened destruction to all knowledge was only a logical determination.

The common term under which, through the accidental use of language, two entirely different ideas were included was another source of confusion.

Thus through the ambiguity of (Greek) Plato, attempting to introduce order into the first chaos of human thought, seems to have confused perception and opinion, and to have failed to distinguish the contingent from the relative.

In the Theaetetus the first of these difficulties begins to clear up; in the Sophist the second; and for this, as well as for other reasons, both these dialogues are probably to be regarded as later than the Republic.
BOOK VI.