American naturalist writer, John Steinbeck is inspired by social facts or the life of humanity of which he has a perfect knowledge to have more or less experienced. His abundant novelistic production places man at the center of his poetics. Thus, he tackles great themes that have become part of the history of literature, such as misery, death, social injustice and freedom. Steinbeck's poetics is thus total as it is interested in the man in all his dimensions: social, political, material, psychological... etc. And one notes thus in the texts of the American author a subversive messianism which confers an existentialist character to his writing. An interrogation of the approach of the characters by the novelistic theory, much better of all the categories of the novel allows to highlight the particularity of the messianic writing in the works of John Steinbeck.