The 1906 book "What Is Man?" by Mark Twain features a discussion about the essence of man between a Young Man and an Old Man. The phrase "what is man, that you are aware of him" is found in Psalm 8:4, which is used in the title. It incorporates psychological egoism, determinism, and free choice beliefs. According to the Old Man, a person is nothing more than a machine that exists just to fulfill one's own wishes and find inner peace. The Young Man protests and asks him to elaborate and give his arguments in support of his stance. Instead of being sarcastic, the essay seems to be an honest and sincere discussion of his beliefs on human nature. He does, however, appear to have had different perspectives on human freedom. Before he wrote "What is Man?," Twain shared the Old Man's opinions. So, readers can read this novel to know human culture in a closure!