LitCharts assigns a color and icon to each theme in The Great Divorce, which you can use to track the themes throughout the work.
At the heart of The Great Divorce (and Christianity) is the concept of free will. The early Christian thinker Saint Augustine proposed a useful way of understanding free will: if a human being acts a certain way, and, under identical circumstances, could have acted differently, then that human has exercised their free will. Lewis never explicitly defines free will in his book, perhaps assuming that his readers already understand what it is. Nevertheless, The Great Divorce suggests that humans can only enter Heaven by exercising their innate free will.
One of the premises of The Great Divorce is that humans have the capacity to choose to go to Heaven even after they die—a notable digression from traditional Christian doctrine, in which souls either go to Heaven or Hell permanently. Humans are born with the power of free will: they can choose where to go, what to think, and—most importantly of all—whether or not to love God. Even in Hell, humans retain their powers of free will, meaning that they can choose to leave Hell and enter Heaven. Over the course of the novel, the Narrator observes the souls of human beings in Hell as they board a bus that takes them to the Valley of the Shadow of Life, located at the outskirts of Heaven. In the Valley, spirits and angels try to convince the souls of humans to love God and give up whatever sin they’re clinging to that is keeping them out of Heaven. If a damned human being chooses to embrace God, they’ll be welcomed into Heaven with open arms—even if they’ve committed horrific sins on Earth. In this way, the novel shows that going to Heaven is the result of a free, personal choice, not an external action (such as going to church, donating to charity, etc.).
Toward the end of the novel, Lewis emphasizes the importance of free will by declining to clarify whether or not God has “planned” humans’ ultimate fate—an idea which, it could be argued, denies the existence of free will. The notion that God knows whether humans will be saved or damned has been interpreted by some Christian thinkers, such as John Calvin, to disprove the existence of free will: for Calvin, free will is just an illusion. However, when the Narrator asks George Macdonald whether or not God knows which human beings will be saved and which human beings will be damned, MacDonald forcefully insists that the Narrator must not ask such a question. Humans must continue to exist in time and space, choosing their own destinies, whereas God, in Lewis’s view, exists outside of time, and so can see what we perceive as the “future” rather as an eternal present. In short, “the mind of God” is beyond human comprehension. MacDonald’s advice suggests that The Great Divorce ’s philosophy of free will is closer to that of the poet John Milton (a major influence on Lewis) than Calvin. Milton argued that God’s foreknowledge of human salvation isn’t mutually exclusive with humans’ ability to choose their own salvation. Even if God does know the fate of humanity, God gives humans the power of free will; therefore, humans can exercise their free will and choose to join God in the afterlife.
While going to Heaven might seem like an obvious choice for one’s free will, the vast majority of the damned souls the Narrator encounters refuse to choose Heaven, suggesting that choosing God—and free will itself—is more difficult than it seems. Many of the damned souls refuse to go to Heaven because they’re frightened. Loving God involves surrendering one’s love of earthly things—other people, one’s pride, art, etc.—and most people are afraid of giving up these things for God. Other damned souls refuse God because they’re under the delusion that damnation and life in Hell are preferable to salvation. For example, the souls of educated, academic human beings smugly suggest that Hell is more conducive to “creativity” than Heaven. (This is a simplified version of William Blake’s argument in The Marriage of Heaven and Hell —an argument that Lewis tries to refute in his novel, even in its very title.) By definition, the concept of free will allows for humans to choose between two or more options. In The Great Divorce , most of the souls the Narrator encounters choose the wrong option—damnation—because they’re confused, prideful, or otherwise corrupted.
Ultimately, the novel shows that free will is potentially dangerous, yet also emancipatory for human beings. If given the option to choose, many people will make the wrong choice, choosing to go to Hell instead of embracing Heaven. Yet the pitfalls of free will make a Christian’s choice to worship God more commendable: the handful of souls who freely choose to love God will be rewarded in Heaven for their difficult decision.