[Footnote 127: Plato, Theæt. p. 207-208 B. [Greek: e)/stin a)/ra meta\ lo/gou o)rthê\ do/xa, ê(\n ou)/pô dei= _e)pistê/mên_ kalei=n.]] [Side-note: 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.] 3. A third meaning of this same word [Greek: lo/gos] or rational explanation, is, that in which it is most commonly understood-To be able to assign some mark whereby the thing to be explained differs from every thing else--to differentiate the thing.[128] Persons, who understand the word in this way, affirm, that so long as you only seize what the thing has in common with other things, you have only a _true opinion_ concerning it: but when you seize what it has peculiar and characteristic, you then possess _knowledge_ of it. Such is their view: but though it seems plausible at first sight (says Sokrates), it will not bear close scrutiny. For in order to have a true opinion about any thing, I must have in my mind not only what it possesses in common with other things, but what it possesses peculiar to itself also. Thus if I have a true opinion about Theætêtus, I must have in my mind not only the attributes which belong to him in common with other men, but also those which belong to him specially and exclusively. Rational explanation ([Greek: lo/gos]) in this sense is already comprehended in true opinion, and is an essential ingredient in it--not any new element superadded. It will not serve therefore as a distinction between true opinion and knowledge.[129] [Footnote 128: Plato, Theætêt. p. 208 C. [Greek: O(/per a)\n oi( polloi\ ei)/poien, to\ e)/chein ti sêmei=on ei)pei=n ô(=| tô=n a(pa/ntôn diaphe/rei to\ e)rôtêthe/n.]] [Footnote 129: Plato, Theætêt. p. 209.] [Side-note: Conclusion of the dialogue--Summing up by Sokrates--Value of the result, although purely negative.] Such is the result (continues Sokrates) of our researches concerning knowledge. We have found that it is neither sensible perception--nor true opinion--nor true opinion along with rational explanation. But what it is, we have not found. Are we still pregnant with any other answer, Theætêtus, or have we brought forth all that is to come?--_I_ have brought forth (replies Theætêtus) more than I had within me, through your furtherance. Well (rejoins Sokrates)--and my obstetric science has pronounced all your offspring to be mere wind, unworthy of being preserved![130] If hereafter you should again become pregnant, your offspring will be all the better for our recent investigation. If on the other hand you should always remain barren, you will be more amiable and less vexatious to your companions--by having a just estimate of yourself and by not believing yourself to know what you really do not know.[131]