The Heart of Gold lands safely on Magrathea. As everybody prepares to venture onto the planet’s surface, Trillian discovers that her pet mice have escaped their cage, but nobody except her seems to care. In fact, they’re too preoccupied with the Heart of Gold’s new voice, which Zaphod explains he changed in the hopes of altering the system’s cloying personality. After a brief argument with Eddie—who has taken on the identity of a nagging parent—the group finally exits the spaceship and makes its way onto the barren landscape of Magrathea. Before long, they come upon a crater created by the sperm whale’s impact. To Zaphod’s delight, the whale’s crash has opened a hole to “the interior of the planet,” which he decides to enter. Excited to venture into a place “where no man has trod these five million years,” he sets off.
Zaphod’s seemingly reckless obsession with Magrathea continues in this scene, as he joyously ventures into a hole in a mysterious planet. If he has ever had any good sense or capacity for self-preservation, he has certainly left it behind at this point. What’s most absurd about his enthusiastic attitude is that he doesn’t even seem to understand why he is so curious about Magrathea, a fact that once again reminds readers that Zaphod has a strange relationship with his own mind.
As the group (minus Arthur and Marvin, who remain above ground) stomps down a passageway, Ford asks Zaphod why he wanted to find Magrathea in the first place. Zaphod answers by saying that he stole the Heart of Gold “to look for a lot of things,” including the planet. Ultimately, though, he doesn’t actually know what he’s looking for. “I only know as much about myself as my mind can work out under its current conditions. And its current conditions are not good,” he says. “I freewheel a lot. I get an idea to do something, and, hey, why not, I do it. I reckon I’ll become President of the Galaxy, and it just happens, it’s easy. I decide to steal this ship. I decide to look for Magrathea, and it all just happens. Yeah, I work out how it can best be done, right, but it always works out.”
In this moment, Zaphod confirms that his decision-making process is fairly odd. He even admits that his mind isn’t currently in “good” condition. Nevertheless, he trusts himself enough to “freewheel” his way through life, following his impulses even when he’s not sure why he wants to do something. This statement reinforces his suspicion that he is keeping something from himself.
Continuing his monologue about the nature of his decision making, Zaphod explains that if he stops to think about why he has done something, he suddenly has an urge to stop pondering his actions. Last night, he says, he was thinking about this strange phenomenon. Wanting to get to the bottom of his mental process, he went to “the ship’s medical bay” and plugged himself into “the encephalographic screen,” where he looked at an overview of “all the tests [he] had to go through under Government medical officers before [his] nomination for presidency could be properly ratified.” After searching in vain for quite some time, he finally discovered “a whole section in the middle of both [of his] brains that related only to each other and not to anything else around them.” According to Zaphod, “some bastard had cauterized all the synapses and electronically traumatized” these sections of his brain.
When Zaphod says that he found two sections of his brain that “relate only to each other and not to anything else around them,” what he’s saying is that somebody has created a secret network between his two brain. In other words, the rest of his brain doesn’t know what’s going on in these two sections. This, it seems, is why he has been feeling like he’s keeping something from himself—indeed, he’s hiding something from the rest of his brain.
When Ford asks who Zaphod thinks did this to him, Zaphod says that the person burned their initials into his brain—a signature of sorts. The letters that he found are “Z.B.”: Zaphod Beeblebrox. Just as he reveals this to Ford and Trillian, “a steel shutter slam[s] down behind them and gas start[s] to pour into the chamber.” Right before the three friends pass out, Zaphod says, “I’ll tell you about it later.”
Despite the fact that Zaphod is often characterized as a bit stupid, it’s worth noting that his suspicions about his own brain have been right all along. After all, he has had a hunch that he is hiding something from himself, and this has turned out to be true in a very literal sense, considering that he was the one to tamper with his own brain in order to keep something hidden.