See also: Mini-essays on chapters 1-2 and chapters 3-4.

In The Creative Habit, Twyla Tharp talks about the “spine” of a work — not the inspiration, which could be a story or image that sparked the initial idea, and not the theme. But the underlying story you started out wanting to tell, no matter how much the finished work ultimately diverged from that story. You, the creator, can clearly see the spine underneath, and the story would not exist without it. And the spine is your guidelight, bringing you through the dark periods where you wonder why you’re even doing this. Because this is the story you want to tell.
She talks about spines as classic archetypal stories: David and Goliath, Romeo and Juliet. Sometimes the spine is visible in the book itself, like Moby Dick where the spine is relentless pursuit of an enemy, and that carries through to the title and the plot. Other times it’s not clear to anyone but the creator. In fact, she cautions creators against revealing the spine of a piece where it would otherwise be hidden, citing a dance that she publicly said was based on a Greek tragedy but had that lineage buried deep. She said it distracted her audience, which was looking for a skeleton of the Greek tragedy that wasn’t there.
One of the exercises she proposes is choosing a work and figuring out what its spine is. So of course I thought of Hitchhiker’s Guide. Is there some archetypal story it’s telling? HHGG is fundamentally, I think, about absurdity and randomness and the futility of trying to control anything. Over and over, its characters make plans and get upset when the plans fail or are rendered useless. The characters who succeed are the ones who have no plan, and go along with whatever is happening — Zaphod, although his chaotic showboating turns out to be masking deep uncertainty — and Trillian, who has a little of Marvin’s dourness but mostly shrugs and adapts.
Is there an archetype about the futility of everything — making plans, building technology, developing rules and civilization? The phrase “fool’s journey” came to mind. Googling reveals that it’s a tarot card. Honestly, I could not understand any of the tarot explanations, or the difference between the fool’s journey and the hero’s journey. The fool is supposed to start out open, spontaneous, and ready to learn. Through a series of events, he matures, seeks relationships with others, and grows into a greater awareness of himself and the world.
This is not quite Arthur Dent, but I could see the fool’s journey as a spine buried beneath the story. Arthur starts out terribly human, concerned about his house and his hangover. By the end of chapter three, his planet has been destroyed and he’s on a Vogon starship. Arthur is a funny mix of open-minded and resistant to the new experiences flooding his system. From page 29, when Ford asks if he has a towel: “He had given up being surprised, there didn’t seem to be any point any longer.” The only thing that does surprise Arthur from then on is the squalid condition of the Vogon hold, full of smelly alien underwear and unwashed cups. Ford puts a fish in his ear; he survives Vogon poetry; confronted with the most powerful computer he has ever encountered, he requests a cup of tea.
On page 192, nearly at the end of the book, Arthur has a conversation with the hapless Slartibartfast, who labored over the Earth and is dismayed that it was destroyed just before fulfilling its purpose.

“Ten million years of planning and work [. . .]. Gone.” He paused. “Well, that’s bureaucracy for you,” he added.
“You know,” said Arthur thoughtfully, “all this explains a lot of things. All through my life I’ve had this strange unaccountable feeling that something was going on in the world, something big, even sinister, and no one would tell me what it was.”
“No,” said the old man, “that’s just perfectly normal paranoia. Everyone in the Universe has that.”
“Everyone?” said Arthur. “Well, if everyone has that perhaps it means something! Perhaps somewhere outside the Universe we know…”
“Maybe. Who cares?” said Slartibartfast before Arthur got too excited. “Perhaps I’m old and tired,” he continued, “but I always think that the chance of finding out what really is going on are so absurdly remote that the only thing to do is to say hang the sense of it and just keep yourself occupied.”

Maybe the point is for it not to be a grand archetype, but the opposite; a journey where the lesson is that life is not necessarily meaningless, but we cannot possibly understand the meaning, so why try? It’s the opposite of a search of enlightenment. It’s a much less grandiose sense that we should just get on with our lives, roll with whatever happens, and not worry about it too much.

Which probably lends itself better to Adams’ comic tone. I think one reason I can read this book over and over is that it hits the right balance of silliness and wisdom, seriousness and absurdity — which for me shifts way over toward silliness and absurdity, but isn’t totally devoid of wisdom and seriousness. And it’s a worldview I share. We may try, but ultimately we can’t understand or control anything; so just do the best you can and try to have a good time.