Since Voldemort's return to his body three years ago, Harry, Ron, and Hermione have gradually been forced to learn that an effective resistance movement is less about showy acts of heroism and more about sustained labor, planning, and the acquisition or protection of valuable information. Harry Potter and the Deathly Hallows takes this idea to its final conclusion: though Harry and his friends do engage in several heroic acts, and though the climax of the novel is a bloody and exciting battle, what Harry spends most of the novel doing—and what allows him to win the final battle—is the information he spends the year acquiring. With this, the novel makes the case that knowledge truly is power, and that devaluing information and learning can have disastrous consequences.
Particularly through Harry's private lessons with Dumbledore last year, Harry began to learn the value of acquiring as much information as possible. Those lessons concerned picking apart Voldemort and Tom Riddle's tragic history in an attempt to better understand the man behind the villain, a quest that Harry and his friends must continue as they leave Hogwarts and go on the run with the goal of tracking down and destroying Voldemort's remaining Horcruxes, objects containing parts of his split soul. With this to guide them, Harry, Ron, and Hermione set out on an undercover quest to obtain as much information as possible, both about the remaining Horcruxes and about Voldemort's whereabouts and activities. Initially, this proves surprisingly unchallenging. Acquiring information from Kreacher gives Harry the intelligence he needs to track down the next Horcrux—a Slytherin locket—infiltrate the Ministry of Magic, and steal it from Dolores Umbridge.
Also at first, Harry ascertains through his mental connection with Voldemort that it seems as though his adversary is on a similar quest to discover important information about wands and wandlore, or the theory of how exactly wands function as they do. This suggests that, at least on some level, Voldemort understands the power of relying on information to inform how he uses his power and doles out violence. However, Harry learns later that Voldemort suffers from significant gaps in how he understands the information he has, which makes him prioritize information that is ultimately less important and devalue a number of things that could've been extremely helpful.
Harry comes to recognize that, though Voldemort makes attempts to learn the theories behind wandlore and the power of blood sacrifices, Voldemort ultimately resorts to brute strength when it proves too difficult and unfruitful to continue pursuing knowledge. This power grab is represented by Voldemort's choice to break into Dumbledore's tomb and steal the Elder Wand. The Elder Wand is supposedly the most powerful wand in the world and can win any duel, no matter what—a proposition that's unsurprisingly attractive to someone like Voldemort, who hasn't been able to thwart Harry by any other means. Harnessing the wand's power, however, isn't as easy as just grabbing it and using it; wandlore is, unfortunately for Voldemort, far more complicated than that. During Harry's final dreamlike conversation with a version of Dumbledore, Harry fills out his understanding of how wands change masters and, ultimately, discovers who the true master of the Elder Wand is: Harry himself. That Voldemort doubles down on his belief that the all-powerful Elder Wand will bring him victory, even when Harry shares this information with him, makes it abundantly clear how little Voldemort thinks of information that doesn't serve him. Harry, on the other hand, is able to use this information to trust that responding to Voldemort's final killing curse with literally any other spell will most likely save him, given that the Elder Wand probably won't kill its own master—and he's right.
Though the conflict between Harry and Voldemort concerning the Elder Wand offers a neat example of the relationship between knowledge and power, it's worth noting that, as a series centered on a school, this relationship is one that shines through all the books in the Harry Potter series. Now an adult (and in that sense, an outsider at Hogwarts), Harry is able to truly see that whoever controls Hogwarts also gets to control Wizarding society more broadly. In other words, controlling the one site at which young people are educated gives a person or group the power to dictate the entire cultural narrative—whether that be championing kindness and camaraderie like Dumbledore did, or blood purity and fear like Snape does under Voldemort's watch—all by choosing what, how, and from whom students learn.
Voldemort indicates that he recognizes this when he first takes over Hogwarts, though it becomes even more apparent during the final battle when he attempts to burn the Sorting Hat. Had Voldemort emerged victorious (declaring that there would be no more Sorting at Hogwarts and that Slytherin House would be the only house), he could have fundamentally shaped society by impressing upon Hogwarts pupils the importance of physical might over intellectual curiosity, and by devaluing or cutting those subjects that he deems useless, such as wandlore or history. In a broader sense, the novel then stands as a call to arms for readers to stand up for varied and diverse education and to remember that many things, from children's stories to the personal accounts of marginalized individuals, have value and are worthy of study.
Knowledge and Power ThemeTracker
Knowledge and Power Quotes in Harry Potter and the Deathly Hallows
He had thought he knew Dumbledore quite well, but ever since reading this obituary he had been forced to recognize that he had barely known him at all. Never once had he imagined Dumbledore's childhood or youth; it was as though he had sprung into being as Harry had known him, venerable and silver-haired and old. The idea of a teenage Dumbledore was simply odd, like trying to imagine a stupid Hermione or a friendly Blast-Ended Skrewt.
Dumbledore would have believed him, he knew it. Dumbledore would have known how and why Harry's wand had acted independently, because Dumbledore always had the answers; he had known about wands, had explained to Harry the strange connection that existed between his wand and Voldemort's...But Dumbledore, like Mad-Eye, like Sirius, like his parents, like his poor owl, all were gone where Harry could never talk to them again.
Harry looked into Doge's earnest, pained face and felt, not reassured, but frustrated. Did Doge really think it was that easy, that Harry could simply choose not to believe? Didn't Doge understand Harry's need to be sure, to know everything?
The accusations he had heard from Muriel at the wedding seemed to have nested in his brain like diseased things, infecting his memories of the wizard he had idolized. Could Dumbledore have let such things happen? Had he been like Dudley, content to watch neglect and abuse as long as it did not affect him? Could he have turned his back on a sister who was being imprisoned and hidden?
"Elf magic isn't like wizard's magic, is it?" said Ron. "I mean, they can Apparate and Disapparate in and out of Hogwarts when we can't."
There was silence as Harry digested this. How could Voldemort have made such a mistake? But even as he thought this, Hermione spoke, and her voice was icy.
"Of course, Voldemort would have considered the ways of house-elves far beneath his notice, just like all the purebloods who treat them like animals...It would never have occurred to him that they might have magic that he didn't."
"Attendance is now compulsory for every young witch and wizard," he replied. "That was announced yesterday. It's a change, because it was never obligatory before. [...] This way, Voldemort will have the whole Wizarding population under his eye from a young age."
The rain was pounding the tent, tears were pouring down Hermione's face, and the excitement of a few minutes before had vanished as if it had never been, a short-lived firework that had flared and died, leaving everything dark, wet, and cold. The sword of Gryffindor was hidden they knew not where, and they were three teenagers in a tent whose only achievement was not, yet, to be dead.
Indeed, as Phineas Nigellus talked about Snape's crackdown, Harry experienced a split second of madness when he imagined simply going back to school to join the destabilization of Snape's regime: being fed, and having a soft bed, and other people being in charge, seemed the most wonderful prospect in the world at that moment.
Dumbledore had left them to grope in the darkness, to wrestle with unknown and undreamed-of terrors, alone and unaided: nothing was explained, nothing was given freely, they had no sword, and now, Harry had no wand. And he had dropped the photograph of the thief, and it would surely be easy now for Voldemort to find out who he was...Voldemort had all the information now...
He was not being kind or generous. As certainly as he had known that the doe was benign, he knew that Ron had to be the one to wield the sword. Dumbledore had at least taught Harry something about certain kinds of magic, of the incalculable power of certain acts.
"Sometimes I've thought, when I've been a bit hacked off, he was having a laugh or—or he just wanted to make it more difficult. But I don't think so, not anymore. He knew what he was doing when he gave me the Deluminator, didn't he?" He—well, [...] he must've known I'd run out on you."
"No," Harry corrected him. "He must've known you'd always want to come back."
He did not want to express the doubts and uncertainties about Dumbledore that had riddled him for months now. He had made his choice while he dug Dobby's grave, he had decided to continue along the winding, dangerous path indicated for him by Albus Dumbledore, to accept that he had not been told everything that he wanted to know, but simply to trust. He had no desire to doubt again; he did not want to hear anything that would deflect him from his purpose.
Dumbledore had warned him against telling anyone but Ron and Hermione about the Horcruxes. Secrets and lies, that's how we grew up, and Albus...he was a natural...Was he turning into Dumbledore, keeping his secrets clutched to his chest, afraid to trust? But Dumbledore had trusted Snape, and where had that led? To murder at the top of the highest tower...
"All right," he said quietly to the other two.
"And are you tempted to join him?"
"No," said Snape, his black eyes on Fleur and Roger's retreating figures. "I am not such a coward."
"No," agreed Dumbledore. "You are a braver man by far than Igor Karkaroff. You know, I sometimes think we Sort too soon..."
And Dumbledore had known that Harry would not duck out, that he would keep going to the end, even though it was his end, because he had taken trouble to get to know him, hadn't he? Dumbledore knew, as Voldemort knew, that Harry would not let anyone else die for him now that he had discovered it was in his power to stop it.
"And his knowledge remained woefully incomplete, Harry! That which Voldemort does not value, he takes no trouble to comprehend. Of house-elves and children's tales, of love, loyalty, and innocence, Voldemort knows and understands nothing. Nothing. That they all have a power beyond his own, a power beyond the reach of any magic, is a truth he has never grasped."
"So Voldemort, instead of asking himself what quality it was in you that had made your wand so strong, what gift you possessed that he did not, naturally set out to find the one wand that, they said, would beat any other. For him, the Elder Wand has become an obsession to rival his obsession with you. He believes that the Elder Wand removes his last weakness and makes him truly invincible."
"Tell me one last thing," said Harry. "Is this real? Or has this been happening inside my head?"
Dumbledore beamed at him, and his voice sounded loud and strong in Harry's ears even though the bright mist was descending again, obscuring his figure.
"Of course it is happening inside your head, Harry, but why on earth should that mean that it is not real?"