Ray Bradbury did not like fantasy

Fahrenheit 451 is science fiction. Science fiction's domain is the possible; fantasy is the realm of the impossible.

Bradbury uses several metaphors to describe the difference between science fiction and fantasy:

1. "Science-fiction is the law-abiding citizen of imaginative literature, obeying the rules, be they physical, social, or psychological, keeping regular hours, eating punctual meals; predictable, certain, sure. Fantasy, on the other hand, is criminal. Each fantasy assaults and breaks a particular law; the crime being hidden by the author's felicitous thought and style which cover the body before blood is seen."
   
2. Science-fiction works hand-in-glove with the universe. Fantasy cracks it down the middle, turns it wrong-side-out, dissolves it to invisibility, walks men through its walls, and fetches incredible circuses to town with sea-serpent, medusa, and chimera displacing zebra, ape, and armadillo."
3. Science-fiction balances you on the cliff. Fantasy shoves you off.