As for me, all I know is I know nothing. Socrates , Phaedrus , sec. To know one's ignorance is the better part of knowledge. However much you study, you cannot know without action. Saadi of Shiraz , Thirteenth century Sufi author .
All phenomena have their causes.
But this unworded lesson, This easy example, Is lost upon men. Lao Zi , Tao Te Ching , no. 43 .