Why does Beatty program the Hound to track Montag even before Montag stole the book?
After Montag meets Clarisse, he begins questioning his occupation and feels like he is living a meaningless life. Montag's depressed attitude and lack of motivation are evident in his mannerisms and disposition. Montag begins to act more aloof and refuses to participate in typical games with the other firemen at work. While the men bet on how fast the Mechanical Hound can hunt down small animals, Montag keeps to himself and lays in his bunk. Captain Beatty recognizes that Montag has become jaded with his occupation and knows that he may have feelings of becoming an intellectual dissident. In order to dissuade Montag from engaging in any illegal activities, like stealing books, Captain Beatty programs the Mechanical Hound to track Montag as a warning. At the beginning of Part Two, Captain Beatty tells Montag,
"Well . . . now you did it. Old Montag wanted to fly near the sun and now that he's burnt his damn wings, he wonders why. Didn't I hint enough when I sent the Hound around your place?" (52)
Essentially, Captain Beatty programs the Mechanical Hound to track and sniff around Montag's apartment in order to dissuade him from stealing books and engaging in intellectual pursuits.
In the novel, Bradbury tells us that books are incorporated into our souls, and change our very being. The Hound is programed to detect the unique chemical “fingerprint” of an individual, down to a biochemical and cellular level. Beatty has already begun to suspect that Montag is changing his thoughts. He is beginning to suspect that Montag is growing suspicious of the concept that books cause confusion, and must be destroyed. Bradbury shows us that when we change what we read, think, and do, it can change us down to the cellular level. Unfortunately, the Hound is already beginning to detect this change in Montag.