what generalization or basic truth in life or human experience is expressed in the essay?

If I had to pick one theme, I would consider the theme of Goodness/Humaneness:

Translated from the word jen or ren, goodness or humaneness is frequently presented in the text as a virtue attained by knowledge and the observation of ritual. It is important to note that the term does not simply mean "good," but speaks to a moral character and attitude that few can hope to possess. It is a complex term outlining a nearly divine presence. As such its attainment can take a lifetime to acquire and years of practiced polishing and re-polishing of one's values and character.