Sokrates refutes this. Suggestion of Theætêtus--That there may be non-cognitions in the mind as well as cognitions, and that false opinion may consist in confounding one with the other. Sokrates rejects this 171 He brings another argument to prove that Cognition is not the same as true opinion. Rhetors persuade or communicate true opinion; but they do not teach or communicate knowledge 172 New answer of Theætêtus--Cognition is true opinion, coupled with rational explanation 173 Criticism on the answer by Sokrates. Analogy of letters and words, primordial elements and compounds. Elements cannot be explained: compounds alone can be explained _ib._ Sokrates refutes this criticism. If the elements are unknowable, the compound must be unknowable also 174 Rational explanation may have one of three different meanings. 1. Description in appropriate language. 2. Enumeration of all the component elements in the compound. In neither of these meanings will the definition of Cognition hold _ib._ Third meaning. To assign some mark, whereby the thing to be explained differs from everything else. The definition will not hold. For rational explanation, in this sense, is already included in true opinion 175 Conclusion of the dialogue--Summing up by Sokrates--Value of the result, although purely negative 176 Remarks on the dialogue. View of Plato. False persuasion of knowledge removed. Importance of such removal _ib._ Formation of the testing or verifying power in men's minds, value of the Theætêtus, as it exhibits Sokrates demolishing his own suggestions 177 Comparison of the Philosopher with the Rhetor. The Rhetor is enslaved to the opinions of auditors 178 The Philosopher is master of his own debates 179 Purpose of dialogue to qualify for a life of philosophical Search _ib._ Difficulties of the Theætêtus are not solved in any other Dialogue 180 Plato considered that the search for Truth was the noblest occupation of life 182 Contrast between the philosopher and the practical statesman--between Knowledge and Opinion 183 CHAPTER XXIX. SOPHISTES--POLITIKUS. Persons and circumstances of the two dialogues 185 Relation of the two dialogues to the Theætêtus 187 Plato declares that his first purpose is to administer a lesson in logical method: the special question chosen, being subordinate to that purpose 188 Method of logical Definition and Division _ib._ Sokrates tries the application of this method, first, upon a vulgar subject. To find the logical place and deduction of the Angler. Superior classes above him. Bisecting division 189 Such a lesson in logical classification was at that time both novel and instructive. No logical manuals then existed 190 Plato describes the Sophist as analogous to an angler. He traces the Sophist by descending subdivision from the acquisitive genus of art 191 The Sophist traced down from the same, by a second and different descending subdivision 192