No lake so still but it has its wave. No circle so perfect but that it has its blur. I would change things for you if I could; As I can't you must take them as they are.
Study the past if you would define the future. I am not one who was born in the possession of knowledge; I am one who is fond of antiquity, and earnest in seeking it there. Learning without thought is labor lost; thought without learning is perilous.
Yin and yang, male and female, strong and weak, rigid and tender, heaven and earth, light and darkness, thunder and lightning, cold and warmth, good and evil...the interplay of opposite principles constitutes the universe.
I do not enlighten those who are not eager to learn, nor arouse those who are not anxious to give an explanation themselves. If I have presented one corner of the square and they cannot come back to me with the other three, I should not go over the points again.