What important theme of realism is reflected in these lines from "Song of Myself" by Walt Whitman?

The important theme of realism that is reflected in the lines from "Song of Myself" by Walt Whitman is the beautiful and harsh realities of life.

He is talking about a corpse, how a man died and his body has decomposed and it is very gruesome. However, he can see past that, and in the future, beautiful flowers are going to grow and nature is going to be wonderful once again.