Final answer:
Vonnegut refers to prisoners as 'human beings' to emphasize their dignity and humanity, challenging their dehumanization and reflecting themes of resilience and freedom in existentialist literature.
Step-by-step explanation:
Kurt Vonnegut often references the prisoners on the trains as 'human beings' to underscore their inherent dignity and humanity despite the extreme dehumanization they are subjected to. Literature, particularly existentialist works, emphasize the distinctiveness of human beings as 'being-for-Itself,' entities with consciousness, subjectivity, and moral agency.
In these works, figures such as Nietzsche and Camus explore themes of freedom, individuality, and the resistance against objectification. This contrasts with the view of human beings as mere objects or 'machines,' an idea reflected in harsh conditions and abuses that strip individuals of their agency and humanity.
Throughout various literary traditions, from Naturalism to Existentialism, authors grapple with the question of what it means to be human under extreme conditions, often highlighting the resilience and inextinguishable nature of human consciousness and freedom.