The predominant theme of Arena is that human beings must acknowledge their doubt in God, confront it, and learn more about themselves to survive. They are placed in dangerous situations that they must survive as individuals and as a group. They can read the manual that they each have received, but after a certain point, they can no longer understand the texts and must wait for someone to guide them through them. Before the humans can use the manual, however, they must be aware that they need it; most of the main characters are so angry at being kidnapped that they toss the manual away or ignore it. They must realize that they need help and guidance to deal with their psychological issues.
These psychological issues are not the only hurdle the humans in the Arena have. Almost all of them have been betrayed by their families, their jobs, or their own desires. They have stopped trusting others and sometimes themselves. Slowly, over the course of months, they learn to trust each other, the manual, and Elhanu, who has given them the manual and provided the safe havens throughout the Arena. Their growth and their conversion, by which they come to accept the help and opinions of others, are slow and steady, constantly pushed by both the dangers of the Arena and Elhanu’s refusal to let them just relax for too long.
The greatest message of the novel is the importance of self-knowledge and the choice to trust in God. While Elhanu never allows anyone to just stay in his safe havens, he also offers them ample opportunities to choose other paths and switch group alliances. Those who become the most self-aware return to Earth with more of their memories intact and a new purpose in life that allows them to pursue their dreams in positive ways.