We will not [says Socrates] then allow our charges, whom we expect to prove good men, being men, to play the parts of women and imitate a woman young or old wrangling with her husband, defying heaven, loudly boasting, fortunate in her own conceit, or involved in misfortune and possessed by grief and lamentation – still less a woman that is sick, in love, or in labor . . . Nor may they imitate slaves, female and male, doing the offices of slaves . . . Nor yet, as it seems, bad men who are cowards and who do the opposite of the things we just now spoke of [things done by men who are “brave, sober, pious, free”], reviling and lampooning one another, speaking foul words in their cups or when sober and in other ways sinning against themselves and others in word and deed after the fashion of such men. And I take it they must not form the habit of likening themselves to madmen either in words nor yet in deeds. For while knowledge they must have both of mad and bad men and women, they must do and imitate nothing of this kind . . . Are they to imitate smiths and other craftsmen or the rowers of triremes and those who call the time to them or other things connected therewith?
I haven't got any idea about the meaning of "for while knowledge" this structure is new for me.
This passage is from the book named: On literature.