Steinbeck employs Jim Casy to articulate some of the novel’s major themes. Most notably, the ex-preacher redefines the concept of holiness, suggesting that the most divine aspect of human experience is to be found on earth, among one’s fellow humans, rather than amid the clouds. As a radical philosopher, a motivator and unifier of men, and a martyr, Casy assumes a role akin to that of Jesus Christ—with whom he also shares his initials. Casy begins the novel uncertain of how to use his talents as a speaker and spiritual healer if not as the leader of a religious congregation. By the end of the novel, he has learned to apply them to his task of organizing the migrant workers. Indeed, Casy comes to believe so strongly in his mission to save the suffering laborers that he willingly gives his life for it. Casy’s teachings prompt the novel’s most dramatic character development, by catalyzing Tom Joad’s transformation into a social activist and man of the people.