Saul Bellow on the Artist's Imperative

How do you judge a work of art? What is the artist's first imperative?

Here's Saul Bellow's take -- from a letter to Alfred Kazin:"The first criterion is enjoyment, and so are the second and third criteria."

Bellow to the young Philip Roth: "I knew when I hit Chicago. . .and read your stories that you were the real thing. When iw as a little kid, there were still blacksmiths around, and I've never forgotten the ring of a real hammer on a real anvil."