I've always felt the quotes work like the faction aptitude test itself—they're the first crack in the system. Look at the iconic 'I want to be brave, and selfless, and smart, and kind, and honest.' It's not just Tris trying to pick a faction; it's her rejecting the premise that you must be only one thing. That's the entire thematic engine of the series right there, the push against a society built on a single, rigid identity. The quotes from the manifestos, especially from Erudite and Dauntless, sound so reasonable in isolation. 'Knowledge is the only logical course' has a chilling appeal. It's only when you see those ideals weaponized that you understand the books' warning about purity. The core isn't just about choosing bravery over knowledge, it's about the danger of any virtue isolated and made absolute.
Even the smaller, quieter lines build this. Four telling Tris, 'Be careful, Beatrice.' It’s a personal warning, but it echoes the larger conflict between cautious calculation and reckless courage. The quotes don't just state themes; they enact the tension. They show characters wrestling with the very ideas the factions represent, which is way more effective than the author just telling us 'the system is flawed.' You get the seduction and the suffocation of it through the words the characters live by, or choose to break.