While many have long believed that Jim Casy embodied Steinbeck's main philosophical beliefs, Tom Joad, completely flawed and human, is the novel's main character. Tom is the character who shows the most development, experiencing what Peter Lisca calls an "education of the heart." This education, gained through experience, intuition, and the teachings of Jim Casy, best exemplifies the moral journey from self to community, from "I" to "we." Tom moves from caring only for himself to a familial loyalty to seeing the entire world as his family.
Tom is kind and often merciful, yet quick to anger and fiercely independent. As a man of action, he embodies one of the novel's main philosophical strands, pragmatism, standing in contrast to the idealistic and talkative Jim Casy. While Casy is predominantly an observer and commentator on the human condition, Tom's acts of humanity are subconscious, his insights and compassion intuitive. Tom is concerned with the practical aspects of his life as they relate to the here and now, not the moral or ideological circumstances surrounding his actions. In this sense, Tom and Casy follow inverted paths in the development of their characters. After Casy has the opportunity to witness his beliefs acted out by the jail inmates, he moves from a position of observation and contemplation to one of action. Tom's social role moves in the opposite direction, from one of action to one of reflection. Not until Tom stops moving and reacting does he have the opportunity to absorb Casy's ideas. When he does so, however, Tom's development comes full-circle as he pledges to return to continue the actions begun by Casy.