Chapters 4 and 5 deal with a question that ties into the motif of existentialism, namely: What is authentic and what is artificial? The question turns up in a variety of ways. Some are subtle, like Hazel learning that all the flowers in the hospital are sprayed with Super Scent, so their scents aren't real. They smell good and like flowers nonetheless, but the scent is artificial. Augustus also makes note of the “cold and artificial” pleasures of the theme park in his soliloquy during their picnic, implying that the pleasures of a theme park are hollow and not really authentic. The authenticity question comes up more directly in Van Houten's reply to Augustus's email, when he asks if “the fleeting jolt of meaning that art gives us” is valuable or not. It's a question at the heart of An Imperial Affliction's symbolism, and The Fault In Our Stars does suggest an answer. The Author's Note says the idea that fiction can matter is “the foundational assumption of our species,” indicating that, at least for John Green, art can have real, i.e. authentic, value. In addition, Hazel obviously finds great meaning in An Imperial Affliction. Reading it and experiencing a story that resonates with and captures her own life provides her with a great deal of comfort. The value Hazel places in the book is quite real, suggesting that art can have authentic value and isn't just, as Van Houten implies, a temporary distraction from life's meaninglessness.
In these chapters we learn a great deal more about Augustus, whose character raises further questions about the idea of authenticity. The way Augustus behaves, such as preparing an entire Dutch-themed picnic, composing and memorizing a soliloquy, arranging to use his wish to take Hazel to Amsterdam, frequently keeping an unlit cigarette in his mouth, and doing things for their metaphorical value, seems like a kind of performance. It's as if he's putting on a persona that isn't necessarily fake but certainly appears calculated. The fact that he goes by two names, “Augustus” with his friends and “Gus” with his parents, also lends weight to the idea that he's constructed a persona. It isn't quite clear whether this persona can be called artificial or inauthentic, but what's obvious is that a sense of grandeur is important to Augustus. We get a hint why in his choice to gleefully sacrifice himself in the video game he and Isaac play. Hazel notes that he talks about the game as if it were real, and we see that he genuinely enjoys the idea of dying gloriously for a worthy cause. All these details imply that Augustus finds value in the idea of being an extraordinary, larger-than-life character, as well as in the idea of sacrificing himself. Throwing himself on a grenade in the game allows him to live out this fantasy, and the desire to be a hero, maybe as much as his attraction to Hazel, could be why he offers his wish to fulfill one of her dreams rather than using it for himself.
The section demonstrates some of the realities of cancer and the ways Hazel and Isaac cope with the emotional turmoil they face. The reality Hazel has to confront is the fact that she'll soon die, inflicting a huge amount of pain on her parents. She deals with it indirectly by fixating elsewhere on An Imperial Affliction. Her obsession with learning the fates of the fictional characters seems to stem from her desire to calm her fears about her own parents. If everything works out for Anna's mother and the Dutch Tulip Man after Anna dies, it means her parents will similarly be alright after her death. The reality Isaac faces is much more immediate, and his response is accordingly much more visceral. He'll soon be blind, and his girlfriend, rather than help him through the ordeal, has chosen to remove herself from the difficult situation. He reacts with volatile mix of sadness and rage, first feeling totally distraught and then exploding in a sobbing, pillow-punching, trophy-smashing outburst. The incident offers us a glimpse at the sort of emotional distress that many cancer patients whose lives will be permanently changed by their illness experience. Augustus, quoting from An Imperial Affliction, articulates an idea that will appear again in the novel as the characters try to deal with the inevitable suffering they'll experience, that pain “demands to be felt.”