What is the theme of this poem by the ancients?

Da Shunyun's poems express his will, and his songs are always said. From the analysis of St. Hume, this meaning is very clear. It is heart-oriented, words are poems, and texts are true, here! Poet, hold also, hold human nature; Three hundred gai, righteousness returns to innocence, which is a kind of training and a symbol.

In fact, poetry also expresses feelings, sadness, sadness, pain, sadness, hatred and resentment ... which can be seen everywhere in poetry at all times and in all countries.