There are three types of irony. Dramatic, verbal, and situational. Dramatic irony occurs when the reader or audience knows something that the characters do not. Verbal irony occurs when what someone says is the opposite of what they mean. Situational irony is when the opposite of what one expects to occur happens.
In Fahrenheit 451, Bradbury sprinkles instances of irony throughout the novel to contribute to the theme of the importance of books.
At the beginning of the book, Montag meets a young neighbor girl named Clarisse as he is walking home from work. Clarisse asks him a question:
They walked still further and the girl said, "Is it true that long ago firemen put fires out instead of going to start them?" "No. Houses. have always been fireproof, take my word for it." "Strange. I heard once that a long time ago houses used to burn by accident and they needed firemen to stop the flames." He laughed.
This is an example of dramatic irony because the reader knows that firemen put out fires. Montag finds Clarisse's question amusing. He believes that fireman have always burned books because this is what society, and his job, have programmed him to think. Montag believes that houses have always been fireproof. It is also ironic that young Clarisse seems to know this basic information, but the adult Montag does not. Clarisse most likely knows this information because she comes from a family who reads. The reader assumes this because of the questions she asks and the knowledge she has that cannot be learned in the mundane classes, mostly sports or television related, that she tells Montag she takes in school. The fact that she has this knowledge, and a grown man does not, shows how important it is to read books.
Montag visits a professor that he once met in the park after calling him on the phone. When Montag gets to his house, the professor is overly cautious. When he sees Montag and insists that he hasn't done anything wrong. Montag convinces the man that he is alone.
The front door opened slowly. Faber peered out, looking very old in the light and very fragile and very much afraid. The old man looked as if he had not been out of the house in years. He and the white plaster walls inside were much the same. There was white in the flesh of his mouth and his cheeks and his hair was white and his eyes had faded, with white in the vague blueness there. Then his eyes touched on the book under Montag's arm and he did not look so old any more and not quite as fragile. Slowly his fear went. "I'm sorry. One has to be careful." He looked at the book under Montag's arm and could not stop. "So it's true."
The irony in this instance is dramatic. The reader already knows that Montag does not wish to investigate the professor. Interestingly enough, Montag could have caught the professor when he first saw him in the park, which makes the reader question why he didn't. Perhaps he subconsciously always had doubts about burning the books. This incident at Faber's house furthers the theme of the importance of books because Faber is paranoid that he will be investigated and have his books burned. When Faber sees the book that Montag has his fear slowly goes away and he continues to stare at the book as if in shock because it is a rare bible, there aren't many left. The fact that Montag even has a book in his hand demonstrates the importance of books; here it is a sign to Faber that Montag can be trusted.
Perhaps the most ironic part of the story is Beatty himself. The irony surrounding Beatty is largely situational. The reader suspects that Beatty knows a lot about books and probably has read them early on, but yet he chooses to be against books and wants to burn them all. At the end of the novel, when he goes to arrest Montag and burn his books, he says,
It was pretty silly, quoting poetry around free and easy like that. It was the act of a silly damn snob. Give a man a few lines of verse and he thinks he's the Lord of all Creation. You think you can walk on water with your books. Well, the world can get by just fine without them. Look where they got you, in slime up to your lip. If I stir the slime with my little finger, you'll drown!
Beatty demeans Montag by making it seem like anyone with a little bit of education or learning automatically thinks they are better than everyone else. He tells Montag how silly it is to repeat verses of a poem, when several lines later he, himself, is making literary references, showing his own hypocrisy. Beatty calls Montag a snob and tells him to quote Shakespeare, but then Beatty quotes Shakespeare; therefore, is he not also what he claims Montag is, a snob?
What'll it be this time? Why don't you belch Shakespeare at me, you fumbling snob? "There is no terror, Cassius, in your threats, for I am arm'd so strong in honesty that they pass by me as an idle wind, which I respect not!" How's that?
These quotations from Beatty enhance the theme of the importance of books. Earlier Beatty told Montag that "We must all be alike. Not everyone born free and equal, as the Constitution says, but everyone made equal." He tells Montag that "A book is a loaded gun in the house next door" and "Who knows who might be the target of the well-read man?" His words are ironic because he is a well-read man and he targets other people who attempt to become well-read by finding them and burning their books.