What Is Man? is Mark Twain's skeptical assessment of free will, and determinism, religious belief, and the nature of humanity. He put off publishing it for 25 years, and then released it anonymously in a limited edition of 250 copies. The book takes the form of a Socratic dialogue between a romantic young idealist and an elderly cynic, who debate such issues as whether man is a machine or a free actor, whether personal merit is meaningless given how our environment shapes who we are, and whether man has any impulse other than pursuing pleasure and avoiding pain. As readers "we listen attentively, leaning forward in our chairs," Charles Johnson writes in his introduction, weighing on our own such statements as the Old Man's claim that "No man ever originates anything.... Men observe and combine, that is all. So does a rat." Linda Wagner-Martin, in the afterword, sees the ideas expressed in this volume as "a thread that runs through even the lightest of Mark Twain's fiction, the calmest of his memoirs; and as the questioning hook that may provide a rationale for his becoming a writer in the first place."