"The delicious food, the white clothes that show when we're dirty, our regulated lives, all of it is to keep up our quality of life as merchandise."
--Emma, The Promised Neverland (season one, episode two)
"You're not that different, are you? Like us humans, demons come in all shapes and sizes, too."
--Emma, The Promised Neverland (season two, episode three)
Animation can tackle or convey deep truths about reality as much as live action. The Promised Neverland rather deeply explores the intelligence of children, the inability to know other minds, the fact that one person does not reflect the individual contents of another person's mind, the injustice of hypocrisy, and the tyranny of classism in the two seasons of its dark fantasy anime. The plot first follows three of the oldest children at the supposed orphanage called Grace Field, Emma, Norman, and Ray, as they decide what to do when Emma and Norman find evidence that their "orphanage" is a farm of sorts to cultivate human flesh for consumption by a race they call demons. Earning high scores on tests can delay the passing over of a child to the demons for killing and consumption, but only up until the child is 12 years old, at which point he or she is sent off regardless of their performance. Emma and Norman desperately scheme to lead themselves and their fellow children away from the demons, thinking of masterful ways to outmaneuver the adults presiding over them.
The Promised Neverland is a storytelling monument to the potential intellectual capacity of children in a sense, though the young protagonists are not always an example of people who intentionally seek out philosophical accuracy. Of course, proving to oneself the objective nature of logical axioms, the depths of consciousness, epistemology, and other miscellaneous truths about the foundations and nature of reality is more significant and deep than any amount of strategizing could ever be, but the planning and counter-planning that the lead characters engage in throughout the first season in particular still require intelligence, and a great deal more than is necessary to just passively live a life of simple practicality. A very young child named Phil noticing things like Sister Krone searching under a bed and that Emma was scared of "Mom" (a human woman who raises them named Isabella) and realizing that there might be something sinister unfolding at Grace Field is an example of this that even involves a character younger than the primary trio.
Eventually, some of the children do indeed escape Grace Field. The escaped children soon run into benevolent demons who call themselves heretics for not consuming humans from the farms as is the typical demon custom (or at least seemingly benevolent in one case, though nothing further comes from this plot thread whatsoever). Named Sonju and Mujika, these demons, along with later demons that Emma observes who have not even abstained from human flesh, prompt Emma to realize that there are actually more similarities between humans and demons than differences despite the oppressive function of the farms like Grace Field. Both are living, sentient mind-body composites that have wills, emotions, desires, and the capacity for elaborate practical and abstract comprehension--or at least both act as if they possess these qualities. Both, furthermore, need to eat to survive, and the ruling elite of the demons have conditioned the lower classes to crave human meat and organs because it grants them human-like physical and mental attributes, all despite hearing that Mujika's blood has the power to cure them of their reliance on eating humans and free them from the shackles of a tyrannical aristocracy.
When it comes to eating, there is a character in the second season who goes so far as to eat the flesh of demon corpses as a sort of hypocritical vengeance. However, she expresses the desire for them to be tortured in ways that she herself says are worse than being simply killed. She says that "Demons deserve worse than death," only to support Ray's plan to kill them all, which would end the demons' suffering, so she is very inconsistent about what she even says she wants or says they deserve. Her philosophical inconsistency and resulting behavioral hypocrisy could only come from stupidity and emotionalism. If something truly is wrong, it is still evil to do it for the sake of releasing mere subjective feelings in reactions to injustice, no matter how intense whatever anger, hatred, or malice a person has is (and the three are very distinct). Moreover, at least if hurting people is universally or mostly wrong, the worst of tortures would be the worst of moral errors, far exceeding literally anything else, including deceiving, murdering, and eating children, in depravity and cruelty.
Emma is shocked by the hypocritical savagery of this girl and her companions, but she herself makes vital philosophical errors in her ideological response. Where Emma so obviously errs is in thinking that logic can be set aside, as if it is not inherently true, that Norman's plan was logical in the values it was aimed at despite him making assumptions rooted in conscience and a longing for self-preservation, and that logic and morality could possibly be in opposition to each other. Norman assumed that it was either morally right to exterminate all demons without even truly considering the option of saving them using Mujika's "evil blood" or that even if his planned actions were evil, it would not matter, because survival matters more than morality (survival is objectively meaningless without morality, so it would have to be the other way around). Regarding the other falsities she puts into words, logic and morality cannot be at odds, for moral obligations can only exist if it is logically possible for them to, and logic is true by necessity, so there is no exception to its intrinsic truth; there is nothing that even God himself could change about the laws of logic.
The hypocritical would-be torturers of demons also overlook that, as someone named Ratri says, humans have treated each other close to how the demons have treated them for centuries: "Do you think what the demons do to you here is bad? It's no different from what humans have been doing to each other for ages now. Well, all except for the child-eating part." Consistency becomes a major theme of the show, especially moral consistency. While The Promised Neverland does not always have what seems to be the mouthpiece character be perfectly consistent, it does address issues that are universally relevant because every generation, every situation, and every creature with the capacity for deep thought has to grapple in some way with such things. What humans have done to each other is actually far worse than what the demons of The Promised Neverland have done, but even when humans mistreat other humans in much more trivial ways, there are those who think the worst of cruelties are justified simply because it will appease their personal emotions.