Love, Dumbledore says repeatedly, is the single most important thing Harry has in his armoury, because it is the only tool he possesses which Voldemort does not.
Conceived through enchantment, abandoned by his father and given up by a mother too heartbroken to live, Voldemort has never experienced love. He cares only about how other humans can serve him, so he will never comprehend the selfless nature of an act like Harry’s mother’s, or that love for a person can overcome obstacles as Snape’s does for Lily, or the benefits of a deep friendship like Harry has with Ron and Hermione.
And he is missing something valuable. Not just because it’s a great shame to live a life without love, but because love is a deeply powerful magic.
‘There is a room in the Department of Mysteries,’ interrupted Dumbledore, ‘that is kept locked at all times. It contains a force that is at once more wonderful and more terrible than death, than human intelligence, than the forces of nature. It is also, perhaps, the most mysterious of the many subjects for study that reside there...’
Harry Potter and the Order of the Phoenix
That love is studied by learned witches and wizards shows it is more than sentiment that brings Dumbledore back to the subject. In the wizarding world, love has literal magical properties, and these keep Harry safe – time and time again.
When Harry faces Voldemort-as-Quirrell, Quirrell is unable to touch him because of the enchantment that lives in Harry’s blood. His mother died to save him, and it has left its mark.
Voldemort doesn’t take this protection seriously, and there’s something else he fails to recognise as significant: the fact that Harry is able to stop Quirrell claiming the Philosopher’s Stone. Dumbledore says later: ‘Have you any idea how few wizards could have seen what you saw in that mirror?’ That Harry, at 11, was thinking not of himself but of preventing harm, should have made his character clear to Voldemort. But he cannot comprehend Harry’s actions, and so he doesn't understand their importance.
Harry’s love and loyalty to Dumbledore allows him to defeat Tom Riddle, the teenage apparition of Voldemort preserved in diary form. It’s also love that sends him into the Chamber in the first place, in the form of friendship. Ron is worried about his sister and both he and Harry are concerned about Hermione, so when Ron says he is going to tell Lockhart about the Basilisk, Harry joins him without hesitation.
In the Chamber, when Harry is once more faced with Voldemort, he announces his loyalty to Dumbledore wildly and without much hope. Yet he is rewarded by the appearance of Fawkes – who distracts the Basilisk and heals Harry’s wounds – and the Sorting Hat, which presents him with the sword of Gryffindor.
In Prisoner of Azkaban, Harry’s love for his lost parents turns a little twisted when he half-wants to be near the Dementors just so he can hear his parents’ dying voices. His connection with his parents is also revealed by the fact that his Patronus is the same as his father’s. Without family, Harry creates relationships that mean just as much to him, from Ron and Hermione to Hagrid and Dumbledore. His readiness to add Lupin and Sirius to this list shows his desire to connect with people.
This ability to love is what will protect Harry, as it gives him the strength to endure what follows. Much later, when he stands in the Forbidden Forest preparing to face Voldemort, he uses the Resurrection Stone to summon Lily, James, Sirius and Lupin, and their presence is his courage.
Having realised the benefits of the protection in Harry’s blood, Voldemort uses Harry to help him return to human form. He intends to take in some of that loving sacrifice, but this is a big mistake. In using Harry’s blood, Voldemort ties the two of them closer together, tethering Harry to life while he, Voldemort, survives. So even as Voldemort thinks he has understood the ancient magic that protects Harry, it thwarts him again.
Voldemort uses Harry’s ability to love against him by luring Harry to the Department of Mysteries in pursuit of Sirius. It works, because Harry is unable to risk not helping a person in need, especially his godfather.
Yet love saves Harry, again, when Voldemort attempts to possess him. Harry is so consumed with grief for Sirius that Voldemort cannot remain inside his head; it causes him agonising pain. Harry experiences the same thing when Dobby dies, and realises that Dumbledore is right – grief is an expression of love, and love keeps Voldemort out.
As Dumbledore and Harry explore Voldemort’s life, his disdain for love remains clear. ‘Nothing I have seen in the world has supported your famous pronouncements that love is more powerful than my kind of magic, Dumbledore,’ Voldemort says in one recollection.
It is this arrogant assumption that led Voldemort to unwittingly provide Harry with tools to defeat him – the opportunity to read his mind, the ability to talk to snakes, the lingering protection of his mother’s sacrifice; these all result from Voldemort’s first attempt to kill Harry.
And so we come to the close. As the spirits of his parents, Sirius and Lupin accompany him into the Forbidden Forest, Harry prepares to make the same sacrifice his mother made for him. His love for his friends, for the memory of his family, for the greater good, is such that he is prepared to die. That, in the end, is what destroys Voldemort.
So why is love such a powerful form of magic? Because, both at the same time, it is a valuable weapon – and a reason for fighting.
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