What are 2 themes in fahrenheit 451

Censorship:

In Fahrenheit 451, owning and reading books is illegal. Members of society focus only on entertainment, immediate gratification and speeding through life. If books are found, they are burned and their owner is arrested. In the book, Bradbury doesn't give a clear explanation of why censorship has become so great in this futuristic society. Rather, the author alludes to a variety of causes. Fast cars, loud music, and massive advertisements create an over stimulated society without room for literature, self-reflection, or appreciation of nature. 
Ignorance/knowledge:

Throughout the novel, the reader is presented with a conflict between knowledge and ignorance. What does true happiness consist of? Is ignorance bliss, or do knowledge and learning provide true happiness? Montag, in his belief that knowledge reigns, fights against a society that embraces and celebrates ignorance.

The fireman's responsibility is to burn books, and therefore destroy knowledge. Through these actions, the firemen promote ignorance to maintain the sameness of society.