[Footnote 132: I have already observed, however, that in one passage of the interrogation carried on by Sokrates (p. 201 A-B, where he is distinguishing between persuasion and teaching) he unconsciously admits the identity between knowledge and sensible perception.] [Footnote 133: See the emphatic passage, p. 195 B-C.] [Side-note: Formation of the testing or verifying power in men's minds, value of the Theætêtus, as it exhibits Sokrates demolishing his own suggestions.] To form in men's minds this testing or verifying power, is one main purpose in Plato's dialogues of Search--and in some of them the predominant purpose; as he himself announces it to be in the Theætêtus. I have already made the same remark before, and I repeat it here; since it is absolutely necessary for appreciating these dialogues of Search in their true bearing and value. To one who does not take account of the negative arm of philosophy, as an auxiliary without which the positive arm will strike at random--half of the Platonic dialogues will teach nothing, and will even appear as enigmas--the Theætêtus among the foremost. Plato excites and strengthens the interior mental wakefulness of the hearer, to judge respecting all affirmative theories, whether coming from himself or from others. This purpose is well served by the manner in which Sokrates more than once in this dialogue first announces, proves, and builds up a theory--then unexpectedly changes his front, disproves, and demolishes it. We are taught that it is not difficult to find a certain stock of affirmative argument which makes the theory look well from a distance: we must inspect closely, and make sure that there are no counter-arguments in the background.[134] The way in which Sokrates pulls to pieces his own theories, is farther instructive, as it illustrates the exhortation previously addressed by him to Theætêtus--not to take offence when his answers were canvassed and shown to be inadmissible.[135] [Footnote 134: Plato, Theætêt. p. 208 E.] [Footnote 135: Plato, Theætêt. p. 151 C.] [Side-note: Comparison of the Philosopher with the Rhetor. The Rhetor is enslaved to the opinions of auditors.]