According to Harlan Ellison. These are Sex, Violence, and Labor Relations.
Those of you who are into things martial will appreciate the essay on the second topic, but they are all most entertaining. Go, read, enjoy.
If you are any kind of fan of science fiction, fantasy, or other speculative fictions, and you haven't read Ellison, you are missing something. And he's just as good a speaker in person as he is on the page.