Mary Shelley's Frankenstein poses existential questions about the identity of man, his relationship with God, his role in the natural world, and the roles of language and morality.
Identity: Who are we? What makes us human, God-like, and monstrous? Who are our allegiances to: our parents, God, or ourselves?
Relationship to God: Are we born into sin? Has God abandoned us? Can we ever really know our Heavenly Father? Should doctors and scientists play God?
Nature: Is nature knowable, insensate, or evil? Can we use it for the betterment of mankind? Should doctors and scientists tamper with nature? Is nature at our disposal, or should we protect it for the future?
Language: Is language acquisition the key to separating us from monsters? Does it lead us to knowledge or destruction? Is it better to express our pain with words or suffer silently?
Morality: Is personal revenge wrong? What mistakes lead to tragedy? Are we bound to extending life by any means necessary, or should we let nature run its course?