First, Beatty lets Montag know that it's ok if he needs a night off. Beatty knows that he really isn't sick, he tells him that every fireman goes through feeling like Montag is and that he need only to understand the why behind his job to get back to work and feeling like himself. He proceeds to tell Montag the history of burning books. He explains the processes of the nature of humans thinking for the past 150 years and he explains to Montag the importance of burning books. H explains how society now has essentially filled its days with activities and starved the mind for real thought as a means of controlling society. He talks about how everyone in society is not created equal, but they are essentially made equal by the environment which they grow up in. If the purpose of society is to produce athletes, then books would be arbitrary. Firemen are in place to control any groups or factions from forming that want to go against the grain and begin to think for themselves.