It is when Beatty goes to visit Montag the morning after the burning of the woman and her books that Beatty explores the philosophy of book burning and shares this with Montag to help him understand the purpose of their profession as bookburners. As a result of the general "dumbing down" of society, books were regarded as being profoundly subversive in the way that they could represent so many ideas and emotions that could produce instability in a society that is governed to ensure "peace of mind." Note what Beatty says to Montag as part of his diatribe:
Someone's written a book on tobacco and cancer of the lungs? The cigarette people are weeping? Burn the book. Serenity, Montag. Peace, Montag. Take your fight outside. Better yet, into the incinerator... Burn all, burn everything. Fire is bright and fire is clean.
To Beatty, therefore, fire becomes a purifying force, a way of erasing difficulties and controversy and helping to maintain the "serenity" and "peace" that supposedly characterises life in this dystopian society. Of course, what Beatty does not talk about is the way that only emptiness has been left after this purging, as Mildred's fascination with a fake family shows.