Symbolism, Imagery, Allegory
How much does the thought of dying scare you? If you answered "A lot. A ton. Make it go away!" then congrats, you're reading the right book. If you answered "Meh. Not a ton. I don't care," we wonder if maybe, just maybe, you don't really believe you're going to die.
For DeLillo, the certainty of our eventual death is what drives us to distract ourselves nearly every second of the day. That's why we get antsy if we sit around for too long without texting, watching TV, playing on the computer, etc. Louis C.K. has a brilliant bit about this, btw. We crave distraction because we don't want to think about what's waiting for us at the end of the line.
But what if our "normal" distractions stop working? Well according to a fictional scientist named Willie Mink, that's when we turn to—ta-da!—drugs that eliminate the part of our brains that makes us afraid of death. Unfortunately, the drug not only makes you forget about death, but also makes you forget the difference between words and reality:
I could not distinguish words from things, so that if someone said "speeding bullet," I would fall to the floor and take cover. (26.36)
Does this side-effect sound symbolic to you? DeLillo is basically hitting us over the head with this idea of language shaping reality more than the other way around. Throughout the book, DeLillo has talked about how radio, TV, and the way we talk to each other has gotten to the point that our words tell us what's real more often than our eyes or ears do. Words totally shape our reality, and as DeLillo shows us, the most powerful use of words in the modern world is to distract us from death.
The problem is that we distract ourselves from thoughts of death so much that we lose track of reality altogether. We've covered over the idea of death with all of our advertisements and TV shows. But what happens when the covering—the media stimuli—is all we know? Then all we have left are the things we say about the world, and not the world itself. DeLillo symbolizes this loss of reality through the effects that Dylar has on the human brain.
The drug makes people forget not just death, but everything that's real. It also makes people forget the difference between the things we say and the things we see, which is just what modern advertising culture does. Remember the most photographed barn in America? The barn becomes the most photographed barn after it calls itself that, not before. Similarly, when Jack says, "falling plane" to Willie Mink, Willie has taken so many Dylars that he starts "gripping the arms of his chair, the first signs of panic building in his eyes" (39.58). Dylar is DeLillo's ultimate symbol for how a culture looking for easy answers (like taking a pill to make everything better) is willing to leave the real world behind just so people won't have to face the hard fact that they're all going to die someday.