The legacy of World War Terminus had diminished in potency; those who could not survive the dust had passed into oblivion years ago, and the dust, weaker now and confronting the strong survivors, only deranged minds and genetic properties. Despite his lead codpiece, the dust—undoubtedly—filtered in and at him, brought him daily, so long as he failed to emigrate, its little load of befouling filth. (1.31)
In this future society, even waking up in the morning and heading to work is an act of perseverance. We have a hard enough time getting up in the morning when the sun is shining, and the birds are singing as they help us dress.
However, just for the heck of it, [Rick] wiggled his bent Sidney's out of his coat pocket, thumbed to ostrich comma male-female, old-young, sick-well, mint-used, and inspected the prices. (3.30)
The desire to keep objects from the past alive and vital, rather than let them decay into oblivion, is a pretty fundamental human trait, at least in modern civilization. It's why the Smithsonian exists, and why pawn shop owners prefer to deal in authentic, mint-condition items. The future deals with animals in pawn shop-type businesses, demonstrating this fact in a seriously surreal way.
The chairs, the carpet, the tables—all had rotted away; they sagged in mutual ruin, victims of the despotic force of time. And of abandonment. No one had lived in this apartment for years; the ruin had become almost complete. (6.17)
The world at large may be decaying, but smaller portions of it—like the home—are a mess, too. Hey, it could be worse. Not even the ravages of time can compete with our freshman dorm rooms.
(Isidore) and the thousands of other specials throughout Terra, all of them moving toward the ash heap. Turning into living kipple. (7.15)
What, did you think human beings were perhaps magically immune from the rot that will overcome everything? Because the answer is no. No, they are not. After that depressing thought, here's some videos featuring adorable kittens.
"But someone has to do this," Phil Resch pointed out.
"They can use androids. Much better if andys do it. I can't anymore; I've had enough. She was a wonderful singer. The planet could have used her. This is insane." (12.50)
Rich finally has an epiphany: he realizes that Luba Luft could have helped humanity persevere in the face of degeneration because her beautiful voice would keep works of art such as Mozart's The Magic Flute alive. Hm. Maybe Rick isn't just a law-abiding citizen hoping to make a few bucks—maybe he's actually an agent of decay and disorder.
"How can I save you," the old man said, "if I can't save myself?" He smiled. "Don't you see? There is no salvation."
"Then what's this for?" Rick demanded. "What are you for?"
"To show you," Wilbur Mercer said, "that you aren't alone. I am here with you and always will be. Go and do your task, even though you know it's wrong." (15.108-110)
Most deities are all about salvation but not Mercer. He treads his own holy path. In connecting other people, Mercer helps give them the strength to persevere even though there's no salvation. It's not exactly "God's son died for your sins," but it's something.
And [the androids], the outstanding members of the illegal group, were also doomed, since if [Rick] failed to get them, someone else would. Time and tide, he thought. The cycle of life. Ending in this, the last twilight. Before the silence of death. He perceived in this a micro-universe, complete. (16.3)
Just in case you forgot how similar android and human life are, here's a quote to remind you. The androids are persevering against "time and tide," just like Rick and the other human characters. Unfortunately, the androids' "twilight"—a.k.a. death—comes in the shape of a name, badge, and laser gun.
Rachael said, "Do you know what the lifespan of a humanoid robot such as myself is? I've been in existence two years. How long do you calculate I have?"
After a hesitation [Rick] said, "About two more years."
"They never could solve that problem. I mean cell replacement. Perpetual or anyhow semi-perpetual renewal. Well, so it goes." (17.8-10)
Unlike Isaac Asimov's "The Bicentennial Man" robots, Dick's androids only live for 4-5 years. That's the same shelf life as Spam. Doesn't this make Rick's job … a little pointless? If Luba Luft would live for only a few years, then why not let her persevere and fill those years singing that sweet, sweet music?
Once, [Rick] fell; clouds of dust obscured everything, and he ran from the dust—he hurried faster, sliding and tumbling on the loose pebbles. Ahead he saw his parked car. I'm back down, he said to himself. I'm off the hill. (21.20)
The mountain sounds a lot like a landscape torn from the underworld. In fact, it reminds us very much of the Sisyphus myth. We're thinking that this scene depicts Rick's perseverance to live, both metaphorically and literally.
"It's the curse on us," Iran said. "That Mercer talks about."
"The dust?" [Rick] asked.
"The killers that found Mercer in his sixteenth year, when they told him he couldn't reverse time and bring things back to life again. So now all he can do is move along with life, going where it goes, to death. […]" (22.41-43)
Life leads to death. That's just the way it goes. The circle of life has been explored in myth, song, and, of course, science fiction novels. But here's Mercer claiming that he could reverse the decay process, and people told him to cease and desist. Who does that?