The Mark Twain work published anonymously in 1906 that deals with determinism is What Is Man? Twain first developed the work years earlier, but privately printed it in a limited edition through the De Vinne Press in 1906 while taking care to conceal his authorship.
The piece is structured as a dialogue between an Old Man and a Young Man. The Old Man argues that human beings are essentially machines shaped by heredity, environment, and preceding circumstances. Their actions, he maintains, arise from the pursuit of personal satisfaction and peace of mind rather than from completely independent free will.
The work explores determinism, free will, psychological egoism, morality, and human nature. Its serious, skeptical tone differs from Twain’s better-known comic novels, which explains why it is sometimes confused with darker works such as The Mysterious Stranger. What Is Man? also echoes Psalm 8:4, “What is man, that thou art mindful of him?”