[Footnote 121: The distinction between persuading and teaching--between creating opinion and imparting knowledge--has been brought to view in the Gorgias, and is noted also in the Timæus. As it stands here, it deserves notice, because Plato not only professes to affirm what _knowledge_ is, but also identifies it with sensible perception. The Dikasts (according to Sokrates) would have _known_ the case, had they been present when it occurred, so as to see and hear it: there is no other way of acquiring knowledge. Hearing the case only by the narration of speakers, they can acquire nothing more than a _true opinion_. Hence we learn wherein consists the difference between the two. That which I see, hear, or apprehend by any sensible perception, I _know_: compare a passage in Sophistes, p. 267 A-B, where [Greek: to\ gignô/skein] is explained in the same way. But that which I learn from the testimony of others amounts to nothing more than opinion; and at best to a true opinion. Plato's reasoning here involves an admission of the very doctrine which he had before taken so much pains to confute--the doctrine that Cognition is Sensible Perception. Yet he takes no notice of the inconsistency. An occasion for sneering at the Rhetors and Dikasts is always tempting to him. So, in the Menon (p. 97 B), the man who has been at Larissa is said to _know_ the road to Larissa; as distinguished from another man who, never having been there, opines correctly which the road is. And in the Sophistes (p. 263) when Plato is illustrating the doctrine that false propositions, as well as true propositions, are possible, and really occur, he selects as his cases, [Greek: Theai/têtos ka/thêtai, Theai/têtos pe/tetai]. That one of these propositions is false and the other true, can be known only by [Greek: ai)/sthêsis]--in the sense of that word commonly understood.] [Side-note: New answer of Theætêtus--Cognition is true opinion, coupled with rational explanation.] Theætêtus now recollects another definition of knowledge, learnt from some one whose name he forgets. Knowledge is (he says) true opinion, coupled with rational explanation. True opinion without such rational explanation, is not knowledge. Those things which do not admit of rational explanation, are not knowable.[122] [Footnote 122: Plato, Theætêt. p. 201 D. [Greek: tê\n me\n meta\ lo/gou a)lêthê= do/xan e)pistê/mên ei)=nai; tê\n de\ a)/logon, e)kto\s e)pistê/mês; kai\ ô(=n me\n mê/ e)sti lo/gos, ou)k e)pistêta\ ei)=nai, _ou(tôsi\ kai\ o)noma/zôn_, a)\ d' e)/chei, e)pistêta/.] The words [Greek: ou(tôsi\ kai\ o)noma/zôn] are intended, according to Heindorf and Schleiermacher, to justify the use of the word [Greek: e)pistêta/], which was then a neologism. Both this definition, and the elucidation of it which Sokrates proceeds to furnish, are announced as borrowed from other persons not named.]