Final answer:
Montag's fear about the lack of critical thinking due to the absence of books and knowledge in society is more justified, as it relates to broader existential threats to humanity in 'Fahrenheit 451'. Mildred's fear is valid in the context of the society's laws, but it is less compelling when considering the long-term consequences. Therefore, Montag's argument has stronger justification.
Step-by-step explanation:
When assessing the fears of Mildred and Montag from Ray Bradbury's Fahrenheit 451, we can conclude that Montag's fear is more justified. Montag's fear stems from the concern that a society without books lacks critical thinking and is doomed to repeat its mistakes. This fear is supported by the narrative, wherein the society is depicted as superficial and oppressive, unable to engage in complex thought and discussion. Montag sees reading and gaining knowledge as a path to personal and societal liberation.
On the other hand, Mildred's fear is a reflection of societal norms that eschew books and consider them dangerous. Mildred's fear is justified within the context of her society's laws and the severe consequences that come with breaking those laws. However, unlike Montag, she does not question the broader implications of such censorship. Instead, she represents the compliant citizen, fearful of the disruption that comes from questioning authority.
Both characters represent valid existential fears within the dystopian setting of their world, but Montag's fear touches upon the fundamental human rights to knowledge and growth. His fear addresses the long-term consequences of ignorance that could ultimately dehumanize society.