子曰：“不愤不启，不悱不发。举一隅不以三隅反，则不复也。”
1The Master said, 'I do not open up the truth to one who is not eager to get knowledge, nor help out any one who is not anxious to explain himself. When I have presented one corner of a subject to any one, and he cannot from it learn the other three, I do not repeat my lesson.'