Why is it appropriate that the "Denham's Dentifrice" commercial keeps interfering with Montag's reading of the Bible in Fahrenheit 451?
I do not think that what the ad was really mattered. I think that what is important here is just that Montag keeps being interrupted and, more importantly, that it is an ad that keeps interrupting him.
Montag is trying to read and think. But his society really does not want people doing these things. Instead, it wants people to focus on material things. This is why it is so appropriate that an ad is distracting Montag -- society wants ads and material things to distract people from thinking.
In Bradbury's Fahrenheit 451, Montag takes the subway to Faber's house. He goes to find out if books have something in them that will fill the void in his life. While on the subway, though, Montag decides he wants to read and memorize parts of the Bible he is holding. When the Denham's Dentifrice ad starts playing over the speakers, it seems abnormally loud. Montag becomes annoyed because he is trying to study, but the other passengers are humming and tapping their toes along with the ad's music. This scene shows the difference between most people, who are conditioned to be a part of this hedonistic society, and Montag, who represents someone emerging from the grips of it. The description of the other passengers is as follows:
"The people whose mouths had been faintly twitching the words Dentifrice Dentifrice Dentifrice . . . were pounded into submission; they did not run, there was no place to run" (79).
It should be noted that these people also don't have any inclination to run like Montag does. The Denham's Dentifrice ad isn't bothering them in any way. In fact, they seem to be enjoying the music and words. They do, however, think that Montag is crazy when he becomes annoyed by the ad as follows:
"'Shut up, shut up, shut up!' It was a plea, a cry so terrible that Montag found himself on his feet, the shocked inhabitants of the loud car staring, moving back from this man with the insane, gorged face . . . The train radio vomited upon Montag, in retaliation . . ." (79).
The above passage seems to personify the radio as an extension of the government's forced regimen of "submission" as it "vomits" the ad out upon Montag and the other passengers. It is as though the radio, not necessarily the ad or the music, is the one bearing down on people and forcing them to pay attention to it and nothing else. The commercial gives Montag the feeling that he is trapped, not just on a subway, but in society, as it forces its way into every aspect of home, work, sleep, and travel. Therefore, the scene on the train is appropriate because it makes the point that Montag is changing while the rest of society is numb to what is really going on in their lives to control them, their thoughts, and their actions.
It is appropriate that the commercial kept interfering with Montag’s reading of the bible in order to demonstrate the extent of the government’s control over people’s minds. Just like in their houses through the TV walls, even while on transit, people’s minds are still being controlled. Through the constant repetition of tailored information from the commercial, people’s minds remain fully engaged to an extent that they have no time to think independently. In addition to that, the transmission was deliberately done at such high volume in order to deter any conversation among commuters. The interruption of Montag’s reading shows that the government had successfully achieved its mission: even Montag, an enlightened individual, could hardly think of anything else other than the commercial.