In Fahrenheit 451, why doesn't Chief Beatty just arrest Montag?
Chief Beatty is a very educated man, one who has a specific outlook on life and one who is dedicated to keeping the rules and principles of the government in order. He has read many books and can use their words to hold up his position while tearing down the strawmen arguements he creates for others. While Montag is sick, Beatty visits him and explains how books needed to be banned to keep people happy and unworried about the real problems in life; he also says that firemen often become fascinated with the books they are charged with burning. Montag asks what happens if a fireman accidentally steals a book.
"A natural error. Curiosity alone," said Beatty. "We don't get over-anxious or mad. We let the fireman keep the book twenty-four hours. If he hasn't burned it by then, we simply come and burn it for him."
(Bradbury, Fahrenheit 451, Google Books)
Beatty's role in society is to keep people from thinking too hard about their lot in life. He is the figurehead of the government at the local level; with his guidance, firemen are feared and people don't want to mess with books. He leaves Montag alone at first because he thinks Montag will get over his unnatural thinking; then, he wants to use Montag to trap other book hoarders. Unfortunately, he underestimates Montag's ability to think outside the box, and he pays with his life.
Beattys role in this novel is to show how corrupt that society is verses our society today. His role is to tell him about the way society used to be, and what firemen used to do. We can tell he is unhappy with his life as when he goes to burn down Montag's house he goes and taunts Montag saying things such as he will arrest him, he will burn down his house, just taunting him as if he wanted to be killed.