What does the Mechanical Hound represent in Fahrenheit 451 by Ray Bradbury?

The Mechanical Hound represents the society's advancements in technology, it's priority to hunt down criminals and to inflict capital punishment, and Captain Beatty's power and authority to execute whomever he wants. The Hound is quite a technologically advanced machine because it operates as follows:

"It's calculators can be set to any combination, so many amino acids, so much sulphur, so much butterfat and alkaline" (26).

This means that anyone's amino acids could be programmed into the Hound and be the next target for killing. The government must have spent a lot of money to create and maintain killing machines like the Hound. This suggests that they value swift punishment without a trial when finding and punishing people with books is concerned. The Hound is only used on those who resist arrest, but there's no talk of a trial on either account, which also shows their no-tolerance policy for book owners.

The Hound is also controlled by Captain Beatty for this fire station. That means that he can program it to find, capture and kill anyone whose information it is given. Montag feels like Beatty must have input some of his own information because the Hound growls at him sometimes. When Montag asks him about this, Beatty says, "It doesn't think anything we don't want it to think" (27). This is a clue that Beatty probably has given the Hound Montag's genetic information. As a result, Montag wonders if Beatty knows about the books he is hiding at his home.

Ultimately, the Mechanical Hound represents the strong arm of the law (Beatty's) against those who own books. It is also an intimidation tool as well as a killing machine. It's too bad that money and technology of that sort is wasted on innocent people who just want to read, rather than on manic drivers who hit people every day on their roads. Montag even says, "That's sad. . . because all we put into it is hunting and finding and killing. What a shame if that's all it can ever know" (27). Montag knows it is a robot/machine, and it doesn't have feelings, but the technology seems to be wasted on killing book owners rather than something more productive.