Warning: Spoilers for both the Looking For Alaska book and Hulu series are ahead.
For most of the novel Looking for Alaska (and the new Hulu adaptation), Miles "Pudge" Halter is kind of a passive character, usually following the lead of his exciting new friends at boarding school. But he does actually set the whole story in motion by making one big move, asking his parents to send him away to school for his junior year. He explains that he's doing this because of the last words of 15th century French writer Francois Rabelais: "I go to seek the Great Perhaps."
"That's why I'm going," Miles tells his parents. "So I don't have to wait until I die to start seeking a Great Perhaps."
Despite this one adventurous impulse, Miles is mostly a rule-following, studious kid. It seems he was bullied a lot back home in Florida, and he coped with that by hanging back and not making much of an impact in school. At his going away party, only two kids showed up, and even they weren't very attached to him. After hearing stories of his dad's days at Culver Creek Academy in Alabama, he decides that there might be an alternate reality in which he becomes a bold prankster who seizes the day, rather than the quiet kid hiding out reading others' famous last words.
So, at Culver Creek, Miles tries to be different. He takes up smoking and joins his roommate, the Colonel, and friends Takumi and Alaska as they plan elaborate pranks on their classmates. While he isn't exactly the one to make things happen, he is gradually opening himself up to new possibilities. Wild days roaming an empty school with Alaska over Thanksgiving, and a crazy weekend spent at the barn drinking terrible wine with all his friends might be part of that "Great Perhaps" he was seeking.
On a grander scale, Miles also explores the meaning of Rabelais' words in his religion class. In a midterm essay, he writes about how religions tackle the question of "What happens after you die?"
"I finally decided that people believed in an afterlife because they couldn't bear not to," he says.
Meanwhile, Alaska is trying to answer the question raised by Simon Bolivar, "How will I ever get out of this labyrinth!" in Gabriel García Márquez's The General in His Labyrinth. She believes the labyrinth is "suffering." We later learn, her personal labyrinth is the guilt she feels over watching her mother die of a brain aneurism when she was 8 years old, and she may or may not have decided to get out of that labyrinth by crashing her car into a police cruiser.
After Alaska's death, those questions become more than theoretical. He finally decides that the Great Perhaps has limitless possibilities, because he does believe in an afterlife of sorts.
"We think that we are invincible because we are," Miles says of teenagers. "We cannot be born, and we cannot die. Like all energy, we can only change shapes and sizes and manifestations. [Adults] forget that when they get old. They get scared of losing and failing. But that part of us greater than the sum of our parts cannot begin and cannot end, and so it cannot fail."
Because he holds onto this concept of immortal energy, he finds a way to believe that Alaska has forgiven her friends for letting her drive off to her death. He also forgives himself for it, and that opens the door for the Great Perhaps to continue.