Finally, while the attempt to attain extreme accuracy of definition was leading to the destruction of all thought and all reality within the Socratic school, the dialectic method had been taken up and parodied in a very coarse style by a class of persons called Eristics. These men had, to some extent, usurped the place of the elder Sophists as paid instructors of youth; but their only accomplishment was to upset every possible assertion by a series of verbal juggles. One of their favourite paradoxes was to deny the reality of falsehood on the Parmenidean principle that ‘nothing cannot exist.’ Plato satirises their method in the _Euthydêmus_, and makes a much more serious attempt to meet it in the _Sophist_; two Dialogues which seem to have been composed not far from one another.[156] The _Sophist_ effects a considerable simplification in the ideal theory by resolving negation into difference, and altogether omitting the notions of unity and plurality,—perhaps as a result of the investigations contained in the _Parmenides_, another dialogue belonging to the same group, where the couple referred to are analysed with great minuteness, and are shown to be infected with numerous self-contradictions. The remaining five ideas of Existence, Sameness, Difference, Rest, and Motion, are allowed to stand; but the fact of their inseparable connexion is brought out with great force and clearness. The enquiry is one of considerable interest, including, as it does, the earliest known analysis of predication, and forming an indispensable link in the transition from Platonic to Aristotelian logic—that is to say, from the theory of definition and classification to the theory of syllogism.