It all comes down to the night that Voldemort tried to kill Harry. Harry's mother dies trying to protect Harry, and in Voldemort's words: "My curse was deflected by the woman's foolish sacrifice, and it rebounded upon me." (GOF 566) Harry is left with a small scar on his forehead, but is otherwise unharmed. The scar, however, has proved to be much more than skin deep. It serves as a link between Harry and Lord Voldemort, a link that has never been satisfactorily explained.
From the beginning, Harry could sense through the scar when Lord Voldemort was near. Eventually the scar also began to hurt when Voldemort was angry. Dumbledore tells Harry "It is my belief that your scar hurts both when Lord Voldemort is near you, and when he is feeling a particularly strong surge of hatred.... Because you and he are connected by the curse that failed. That is no ordinary scar" (GOF 521). No ordinary scar indeed. The connection becomes even deeper after the Dark Lord regains his body, and in Order of the Phoenix, Harry begins to sense a range of emotions from the Dark Lord, as well as sharing Voldemort's thoughts and visions. Snape tells Harry that "The curse that failed to kill you seems to have forged some kind of connection between you and the Dark Lord... when your mind is most relaxed and vulnerable - when you are asleep, for instance - you are sharing the Dark Lord's thoughts and emotions" (OOTP 469). Perhaps the most disturbing instance of this occurs when Harry witnesses the attempted murder of Arthur Weasley. He sees the attack as if he himself were the snake biting Mr. Weasley.
Snape has an explanation for this as well: "You seem to have visited the snake's mind because that was where the Dark Lord was at that particular moment... He was possessing the snake at the time and so you dreamed you were inside it, too" (OOTP 470). Later on in Dumbledore's office, Harry experiences a disturbing urge to attack Dumbledore: "At once, Harry's scar burned white-hot, as though the old wound had burst open again - and unbidden, unwanted, but terrifyingly strong, there rose within Harry a hatred so powerful he felt, for that instant, he would like nothing better than to strike - to bite - to sink his fangs into the man before him -" (OOTP 419). Harry later says "it was like something rose up inside me, like there's a snake inside me" (OOTP 425). Is there something inside Harry, some evil thing fighting to get out?
It would definitely seem to support the Horcrux theory. Except that in Half-Blood Prince, the scar abruptly stops hurting and Harry can no longer sense anything from Voldemort. Dumbledore explains that "Lord Voldemort has finally realised the dangerous access to his thoughts and feelings you have been enjoying. It appears that he is now emplying Occlumency against you" (HBP 61). If the thoughts and feelings had been coming from within Harry, from a piece of Voldemort's soul, then Voldemort employing Occlumency wouldn't stop them. So there's no evidence to support that Harry has a horcrux inside him. And if you really want to believe that, then I suggest you stop reading here. Because that's not the end of the story.
While the emotions Harry was feeling were coming from outside himself, it is the connection between him and Lord Voldemort itself that is allowing those emotions to reach him. When Dumbledore is talking to Harry about the Horcruxes, one possibility he suggests is that Nagini the snake is a horcrux. He bases this on the fact that the snake's behaviour is rather strange and that Voldemort "seems to have an unusual amount of control over her, even for a Parselmouth" (HBP 473). This seems to suggest that the Horcrux would create a connection between Voldemort and the snake that would allow him to control her more. Sound familiar?
The other part we're forgetting is that Harry is not just experiencing Voldemort's thoughts and emotions. He has also inherited some of his abilities. In second year, Harry discovers that he is a parselmouth. He can talk to snakes, an ability that Voldemort was well-known for. Harry wonders why he has this ability in common with Voldemort in this telling conversation with Dumbledore:
"You can speak Parseltongue, Harry, because Lord Voldemort - who is the last remaining descendant of Salazar Slytherin - can speak Parseltongue. Unless I'm much mistaken, he transferred some of his own powers to you the night he gave you that scar. Not something he intended to do, I'm sure..."Voldemort put a bit of himself in me... Sounds like a horcrux to me. It is one thing to have a connection to someone else's mind, it is quite another to transfer your in-born abilities to them.
"Voldemort put a bit of himself in me?" Harry said, thunderstruck.
"It certainly seems so." (COS 245)
So let's, for now, assume that Harry is a Horcrux. How did it happen? As Dumbledore indicates above, Voldemort surely did not intend to make Harry a Horcrux. But he did intend to make one that night: "if my calculations are correct, Voldemort was still at least one Horcrux short of his goal of six when he entered your parents' house with the intention of killing you....I am sure that he was intending to make his final Horcrux with your death" (HBP 473). So how is a Horcrux actually made? Slughorn explains to Riddle that "Killing rips the soul apart. The wizard intent upon creating a Horcrux would use the damage to his advantage: he would encase the torn portion...There is a spell" (HBP 465). So to create a Horcrux, one must first kill someone, then encase the torn part of the soul inside an object using a spell. Without knowing more about the spell, it's really hard to say if the procedure could have happened by accident. Is the spell something that you set up ahead of time, and then at the moment of killing set into motion? And then there is the larger glitch in this little theory: to set up a Horcrux, you have to kill. Dumbledore thinks that Voldemort was going to use Harry's death, NOT the death of his mother or father, to create the final Horcrux. But Harry didn't die that night. No death = No Horcrux. Or is it possible that merely the intent of killing Harry was enough to rip Voldemort's soul? Again, without knowing more about how the spell works, it's hard to say.
Another question to consider here is why doesn't Voldemort realise that Harry is a Horcrux? He obviously doesn't know that Harry is a Horcrux because he keeps trying to do him in, and surely he wouldn't do that if he knew. We do know that Voldemort cannot sense Horcruxes after they have been separated from his body. Harry asks Dumbledore that exact question:
"Does Voldemort know when a Horcrux is destroyed sir? Can he feel it?"But would Voldemort feel it when a Horcrux has been newly created? Would he not feel his soul being torn and sealed away? Would he not realise that the spell had been performed? One could argue that in the shock of the rebounding curse and him losing his body, Voldemort could have overlooked the fact that another piece of his soul was missing. Or perhaps he realised it was missing, but thought the spell had gone as planned and went into the intended object, and not Harry. Or maybe he does realise that Harry's a horcrux and is simply willing to sacrifice a bit of his soul in order to be rid of his prophesied nemesis.
"I believe not. I believe that Voldemort is now so immersed in evil, and these crucial parts of himself have been detached for so long, he does not feel as we do." (HBP 474)
Another question to consider is if a piece of Voldemort's soul could actually reside comfortably in Harry's body. In Order of the Phoenix Voldemort takes possesion of Harry's body. But he cannot remain because Harry begins to think of the people he loves. As Dumbledore says, "That power [to love] also saved you from posession by Voldemort, because he could not bear to reside in a body so full of the force he detests." (OOTP 743). If Voldemort couldn't stand to stay in Harry's body, then how could a piece of his soul?
In Order of the Phoenix, after Harry has the dream about the snake attacking Mr. Weasley, there is an odd little scene where Dumbledore consults some of his instruments. We don't hear the question Dumbledore asks, but a serpent made of smoke appears:
"Naturally, naturally," murmured Dumbledore apparently to himself, still observing the stream of smoke without the slightest sign of surprise. "But in essence divided?"I really wish that I understood this part better, because I think it's key to understanding the nature of Harry's connection with Voldemort. Two serpents, in essence divided. Does Dumbledore mean that Harry and Voldemort are divided, even though they were sharing the mind of the snake? Or does he mean that Voldemort is divided, one part of his soul in his own body, the other residing in Harry's? Does it support or contradict the theory of Harry as a Horcrux?
Harry could make neither head nor tail of this question. The smoke serpent, however, split itself instantly into two snakes, both coiling and undulating in the dark air. With a look of grim satisfaction, Dubledore gave the instrument another gentle tap with his wand: the clinking noise slowed and died and the smoke serpents grew faint, became a formless haze and vanished." (OOTP 416)
Which brings me to my next question: If Harry is a Horcrux, then why doesn't Dumbledore tell him? Surely Dumbledore would know. After the snake attack on Mr. Weasley, Mrs. Weasley remarks that "Dumbledore seems almost to have been waiting for Harry to see something like this" (OOTP 434). Dumbledore seems to understand what the connection between Harry and Voldemort means. But he never mentions the possibility that Harry is a Horcrux. And after the end of Order of the Phoenix he said he was done protecting Harry. But maybe he has his reasons. Maybe it's not about protecting Harry, but just realising that this is something that Harry needs to find out on his own and come to accept.
So, final word. Is Harry a Horcrux? Well, there are some fairly large holes in the theory, as I have pointed out above. And yet there is strong evidence that would support it. The connection between Harry and Voldemort has never been adequately explained otherwise. But I'm not sure I'm entirely convinced. What do you all think?