Laotzu's Tao and Wu Wei, by Dwight Goddard and Henri Borel, [1919], at sacred-texts.com
To recognize one's ignorance of unknowable things is mental health, and to be ignorant of knowable things is sickness. Only by grieving over ignorance of knowable things are we in p. 48 mental health. The wise man is wise because he understands his ignorance and is grieved over it.