Knowledge as Experience
The entire narrative is structured to reveal the experiences in Jamal’s past in which he gained the knowledge that he uses to answer the quiz questions. Thus, the film shows how people can gain knowledge through experience in often-unexpected ways. The reason people (like the show's host) question Jamal's competence on Who Wants to be a Millionaire? is that he is an uneducated "slumdog," and therefore an extremely unlikely victor. He cannot answer simple questions about Indian geography, yet he knows who is on the American hundred dollar bill. Many people in the film take a dismissive attitude towards Jamal's flukey ability to know the answers to all these questions, but he still has the last laugh when he wins the game show. Thus, the fact of Jamal's victory throws into question the nature of knowledge, and the film asks: is education the only path to knowledge, or can experience also lead to surprising wisdom?
Redemption
The flashbacks to when the brothers were kids reveals a close familial bond between Jamal and Salim, but it also becomes clear that through their struggles, the brothers set off on two very different ethical paths. While Jamal embraces a strong moral center, Salim embraces the life of a gangster, and falls in with the wrong sorts of people. Salim gets more and more caught up in shady dealings, and does not always play fair, such as when he steals Latika away from Jamal and when he begins working for Javed. By the end of the film, however, just when it seems that Salim has fully gone over to the "dark side," he decides to help Latika and sacrifice himself for her wellbeing. In this way, he dies nobly, right by his god, and right by his childhood friends. Thus, a major thematic thread in the film is the notion of redemption.
Fate vs. Free Will
Fate, the sense that destiny is predetermined to a certain extent by virtue of a higher power, is alluded to in the very first moments of the film. The reason Jamal does so well on the game show, the film suggests, is simply because "It is written." This notion of destiny being "written," of certain events happening simply because they were meant to, is one of the film's underlying themes. The fact that all of the questions on the game show seem tailored to reflect some pivotal moment of Jamal's life experience is only further testament to the fact that there is something fated about his experience on the show.
Throughout the film, events converge in unlikely ways, and the line between free will/action and luck/chance becomes blurred. Especially at the end, events come together in accidentally-perfect ways, suggesting that fate has had a hand in the proceedings. Latika manages to tune into the show just as Jamal is phoning Salim, and she manages to pick it up just before the producers give up on her. Then, the final question is one that directly pertains to The Three Musketeers, an emblem of his childhood connection to Latika and Salim—and even though this connection doesn't give Jamal the answer, as would be expected, he manages to guess the right answer without any hints.
Love and Loyalty
Jamal spends much of the film fighting to survive in difficult circumstances, and the thing that drives him to survive and fight for his life is his unending devotion to his childhood sweetheart, Latika. Indeed, the reason he goes on as a contestant on Who Wants to Be a Millionaire? is because he thinks Latika might be watching and it might give him a way of reuniting with her.
While Salim is driven by his desire for power and money, Jamal is driven by his love and his desire to save Latika from falling victim to evil men. When he and Jamal first arrive in Mumbai after years of travel, he goes around asking anyone he can find if they have seen Latika, and while Salim wants to abandon the thought of her completely, Jamal is driven by his desire to find her. We see flashes of Latika smiling up at him from the train platform throughout the film, thus showing us that his love for Latika is a driving force in his life.
Upward Mobility
Jamal becomes a huge celebrity with his appearance on Who Wants to Be a Millionaire? not only because he does so well, but because his success on the show seems accidental and unusual given his class position. The fact that he is uneducated and poor makes his success all the more miraculous, as audiences marvel at his ability to suceed just when it seems that he will fail. Thus, Jamal's trajectory is compelling precisely because it follows someone beating the odds to become upwardly mobile. The audience laughs at his lack of education and his status as a chaiwala at the beginning of the film, but soon enough the host is telling him that he is making more money than anyone who he has ever worked for.
Escape
A major theme in the film is escape. In one of the first scenes, we see Jamal being brought in for questioning about how he is doing so well on the game show. He has been kidnapped by the police and we are immediately curious how he will escape from their clutches and the torture he endures. Then, as he narrates his biography, we see that he has had to escape nearly everywhere he's ever lived. First, we see him escaping from a locked toilet in a disgustingly comical way, then we see him escaping the Bombay riots after witnessing the death of his mother, then escaping a child begging ring right as he is about to be blinded by Maman. The rest of the film follows Jamal as he works to help Latika escape from her fate, and what drives the narrative and ups the suspense is the promise of their final escape from their difficult circumstances and their ability to live together in peace and happiness.
Companionship
A recurring reference in the film is Alexandre Dumas' novel The Three Musketeers, about a loyal band of musketeers who fight for the common good. While Jamal, Salim, and Latika are not actually familiar with the plot of this book, they identify themselves as characters in it, and see their companionship as akin to the companionship of the three musketeers. They do not need to know the plot of the novel to know that its title refers to companionship and togetherness, and the image of the characters, however abstract, binds them together, even through grave betrayals and separations.
