John Steinbeck uses religion within Grapes of Wrath to explore guilt, hypocrisy, and reformed faith. This theme is first introduced through Jim Casy, an ex-preacher. Casy feels guilty for no longer feeling love for Christianity or for Jesus. He feels he has been a hypocrite in his religious practices in that he would often have sex with random women when possessed with the “Holy Sperit.” After reflecting on his actions and on the actions of people in general, Casy chooses to believe there is no sin or virtue, and that actions are just “stuff people do.” Further, he finds he doesn’t love Jesus, but he does love people; for Casy, humans are divine.

Casy’s religious reformation shares similarities with transcendentalism, the tenets of which were espoused by the likes of Ralph Waldo Emerson and Henry David Thoreau. Casy's religious belief revolves around a love for all people, and a belief in the existence of a singular soul of which all humans possess a small piece. Transcendentalism similarly holds a belief of something called the “Oversoul,” which is a divine spirit or soul that encompasses all humans.

This idea of the “Oversoul” is a theme that evolves in Grapes of Wrath. When Tom Joad realizes he must help others, he remembers Casy’s musings about how humans were all part of just one soul. Tom takes this belief and uses it to reinforce his decisions to help those in need; he also shares this with Ma Joad in an effort to comfort her. Furthermore, a core belief of transcendentalism is the acceptance of all humans as inherently good. Casy mirrors this by choosing to love all humans and rejecting sin as a viable concept. Casy’s belief and effort to love all humans is reflected in not only his character but in other main characters as well:

• Ma Joad, Tom Joad, and Rosasharn all freely give love to others, and in doing so they heighten the quality of life for themselves and those surrounding them.

Steinbeck uses Casy’s reformed religious beliefs as an alternative to strict religious doctrine. In doing so, The Grapes of Wrath reflects a love for everyone, especially for those who are in need.

When Steinbeck explores Christianity within The Grapes of Wrath, readers are introduced to it through characters such as Granma or the religious fanatic at the Weedpatch camp. These characters show the downside and overall hypocrisy of a strict, uncompromising approach to Christian doctrine. Granma’s belief is described as nearly violent; yet, when listening to the rambling and fairly un-Christian prayer of Casy over breakfast, she does not hear him, and blindly follows with “amen” and “pu-raise God!” at any pause in Casy’s speech. Granma’s religious belief has degraded to the point that she is unable to truly listen, ask questions, or change—yet, she still believes herself to be devoutly religious, despite her lack of effort or understanding.

Similarly, the religiously fanatic woman that Rosasharn meets at the Weedpatch camp only works to spread misery with her beliefs. She hypocritically claims that other actions are sinful, all the while spreading misery and fear with her religious proclamations.

• For example, the religious woman views dancing as sinful and tells Rosasharn that she’ll have a miscarriage if she goes to the camp’s Saturday dance.

Steinbeck portrays the heavily religious, hypocritical characters as more damaging to themselves or other people’s happiness than those who are unsure, guilty, or express unorthodox  beliefs, like Casy.