In a former chapter, I tried to elucidate the general character and purpose of those Dialogues of Search, which occupy more than half the Thrasyllean Canon, and of which we have already reviewed two or three specimens--Euthyphron, Alkibiadês, &c. We have seen that they are distinguished by the absence of any affirmative conclusion: that they prove nothing, but only, at the most, disprove one or more supposable solutions: that they are not processes in which one man who knows communicates his knowledge to ignorant hearers, but in which all are alike ignorant, and all are employed, either in groping, or guessing, or testing the guesses of the rest. We have farther seen that the value of these Dialogues depends upon the Platonic theory about knowledge; that Plato did not consider any one to know, who could not explain to others all that he knew, reply to the cross-examination of a Sokratic Elenchus, and cross-examine others to test their knowledge: that knowledge in this sense could not be attained by hearing, or reading, or committing to memory a theorem, together with the steps of reasoning which directly conducted to it:--but that there was required, besides, an acquaintance with many counter-theorems, each having more or less appearance of truth; as well as with various embarrassing aspects and plausible delusions on the subject, which an expert cross-examiner would not fail to urge. Unless you are practised in meeting all the difficulties which he can devise, you cannot be said _to know_. Moreover, it is in this last portion of the conditions of knowledge, that most aspirants are found wanting. [Side-note: The Hippias is an exemplification of this theory--Sokrates sets forth a case of confusion, and avows his inability to clear it up. Confusion shown up in the Lesser Hippias--Error in the Greater.]