According to Frederick I. Carpenter in his essay, "The Philosophical Joads," Steinbeck's social thought seems to be shaped by three distinct strands of nineteenth century American philosophy: the Emersonian concept of the Oversoul, the idea of a humanism expressed by the love of all persons and the embracing of mass democracy found in the works of Walt Whitman and Carl Sandburg, and the pragmatism of Henry James.
The Transcendental concept of the Oversoul is expressed in the earthy folk language of Jim Casy as the belief that all human's souls are really just part of one big soul. Ralph Waldo Emerson, the most well known proponent of transcendentalism, defined the Oversoul as the universal mind or spirit that animates, motivates, and is the unifying principle of all living things. Casy makes numerous references to this one large soul that connects all in holiness, and they dovetail nicely with the basic idea of strength in group unity. Somewhat conversely, American transcendentalism also recognized individualism, a faith in common people and their self-reliance. This concept of the survival of the human life force is symbolized by the survival of the land turtle and Ma's comment, "We're the people — we go on." This combination of rugged individualism and an embracing of all men as part of the same Great Being is physically expressed in the education and re-birth of Tom Joad: His strongly individual nature gives him the strength to fight for the social welfare of all humanity.
