Though knowledge cannot be first communicated by written matters, yet if it has been once communicated and subsequently forgotten, it may be revived by written matters. Writing has thus a real, though secondary, usefulness, as a memorandum. And Plato doubtless accounted written dialogues the most useful of all written compositions, because they imitated portions of that long oral process whereby alone knowledge had been originally generated. His dialogues were reports of the conversations purporting to have been held by Sokrates with others. [Side-note: Plato's didactic theories are pitched too high to be realised.] It is an excellent feature in the didactic theories of Plato, that they distinguish so pointedly between the passive and active conditions of the intellect; and that they postulate as indispensable, an habitual and cultivated mental activity, worked up by slow, long-continued, colloquy. To read or hear, and then to commit to memory, are in his view elegant recreations, but nothing more. But while, on this point, Plato's didactic theories deserve admiration, we must remark on the other hand that they are pitched so high as to exceed human force, and to overpass all possibility of being realised.[127] They mark out an _idéal_, which no person ever attained, either then or since--like the Platonic theory of rhetoric. To be master of any subject, in the extent and perfection required for sustaining and administering a Sokratic cross-examination--is a condition which scarce any one can ever fulfil: certainly no one, except upon a small range of subjects. Assuredly, Plato himself never fulfilled it. [Footnote 127: A remark made by Sextus Empiricus (upon another doctrine which he is discussing) may be applied to this view of Plato--[Greek: to\ de\ le/gein o(/ti tê=| diomalismô=| tô=n pra/xeôn katalamba/nomen to\n e)/chonta tê\n peri\ to\n bi/on te/chnên, _u(perphtheggome/nôn e)/sti tê\n a)nthrô/pôn phu/sin_, kai\ eu)chome/nôn ma=llon ê)\ a)lêthê= lego/ntôn] (Pyrrh. Hyp. iii. 244).] [Side-note: No one has ever been found competent to solve the difficulties raised by Sokrates, Arkesilaus, Karneades, and the negative vein of philosophy.]