You must purify your own ruling faculty, and hold to this plan of life. ‘From this time forth, the material I must work upon is my own mind, as wood is the material of a carpenter or leather that of a shoemaker […] and even this preparation is by no means sufficient for a true philosopher: he must know he has been sent as a messenger from Zeus to men concerning what is good and evil; to show them that they have gone astray, and are seeking the true nature of good and evil where it is not, without ever considering where it really is. (Discourses)
