Clay is fashioned into vessels; it is on their empty hollowness that their use depends. Doors and windows are cut out to make a dwelling, and on the empty space within, its use depends. Thus, while the existence of things may be good, it is the non-existence in them that makes them serviceable.
LaoziTo know people is wisdom, but to know yourself is enlightenment. to master people takes force, but to master yourself takes strength. to know contentment is wealth, and to live with strength resolve. to never leave whatever you are is to abide, and to die without getting lost- that is to live on and on.
Laozi