Thinking about depth as a quality of mind meant thinking about the stillness and depth of water, which itself seeks depth.
But how is depth the correct dimension with which to measure quality of mind? Experience, knowledge, knowledge of causes and relations…: aren’t these things are better measured for mass, breadth and width, and speed?
Or there is “psychological depth” – knowing those demons within, your deepest fears, shame, humiliation.
Depth is a measure of humility; depth as a measure of quality of mind is measure of humility of mind: are you humble in your thoughts? How can I make myself humble?
Depth = how deeply do you bow? Do your efforts begin and end in prayer?
Depth = seek the company of those at the bottom (where none would like to be): to be overbearing when one has wealth and position is to bring calamity upon oneself.
Depth = act in service: to retire when the task is accomplished is the way of heaven.