Why did Professor Dumbledore name six Horcruxes, but withhold that he believed a piece of Voldemort’s soul was attached to Harry, as the Horcrux Voldemort never intended to make?
Because it would have led to the obvious question: “How do I separate myself from Voldemort’s piece of soul, Professor?”
Or, more likely, “How are YOU going to remove Voldemort’s piece of soul from me, Professor?”
Right? Because Dumbledore knew Harry would have to go in front of Voldemort’s Killing Curse. And Albus didn’t have a damn clue how to pull Harry and Voldemort apart without destroying Harry, at least not for the first fifteen years of Harry’s life.
(By the way, this answer assumes Dumbledore knew — or at least, suspected — that, at Godric’s Hollow, a piece of Voldemort’s soul attached itself to Harry, and that’s why Harry survived Voldemort’s Killing Curse.)
It wasn’t until Voldemort reanimated himself by taking Harry’s blood that Professor Dumbledore got that gleam in his eye, and felt like there was a chance Harry might actually survive, after all.
Because, what do we know about Horcruxes? The only way to destroy one is to annihilate the vessel containing the piece of damaged soul.
So, can we imagine what it would have been like to be in Dumbledore’s shoes, staring into the innocent eyes of a kid who never wanted any of this, who just wanted to be normal, like all of his friends and peers?
How would any of us like to have that conversation with a first-, third-, or fifth-year student… Hell, a kid of any age?
So, I don’t blame Dumbledore for keeping that little tidbit to himself, taking it to the grave with him. Because it was a morbid thing Dumbledore was planning to do, convincing and manipulating Harry into putting himself in front of Voldemort.
And for about thirteen years prior to the events at Little Hangleton Cemetery, Dumbledore probably didn’t see how Harry could possibly survive, once Lily’s magical love shield evaporated upon Harry’s coming of age on his seventeenth birthday.
After all, nothing lasts forever, and once Harry left Privet Drive forever, not only would he lose the protection Albus had cast around the Dursley home, Lily Potter’s magic was presumably going to evaporate, once and for all.
Meaning, until Harry was whisked away by portkey to Little Hangleton Cemetery, Dumbledore probably wanted Voldemort to cast that Avada Kedavra curse at Harry sooner than later, while Harry was still under his mother’s protective love-charm.
So, it was no wonder Dumbledore got that gleam in his eye when he discovered Voldemort had used Harry’s blood to come back to life. It meant that now Harry and Voldemort shared blood, and that meant all kinds of fun stuff when it comes to wands, cores, and death sticks. Some of us would even say, that was part of Dumbledore’s plan, all along, anyway, right?
(Although, if that’s true, it just means Dumbledore’s “plan” inadvertently got Cedric Diggory killed, if Dumbledore knew Voldemort was trying to capture Harry Potter through the Triwizard Tournament, and Dumbledore let the tournament play out anyway. Sorry, Cedric. Sorry, Diggory Family. The Greater Good, collateral damage, and all that. Or maybe we should just stick to “binding magical contract.”)
Ultimately, Dumbledore knew Harry’s life would be put at risk. Dumbledore knew Harry had a good chance of surviving, sharing the Potter blood with Voldemort.
But, Albus also didn’t really know for sure, or the conversation would have gone something like this:
“How can we separate Voldemort’s soul from me, Professor?” Harry asked. “Well, Harry, as I said, there’s only one way to destroy a Horcrux. The vessel in which it is contained must be destroyed.” “The vessel, Professor? You mean… me?” Dumbledore remains silent, his clear eyes becoming glassy; he suddenly busies himself cleaning his glasses. A quiet, but audible noise emanates from the old headmaster; it might have been a sniffle. The ominous silence inebriates Harry; Voldemort’s constant, distant, overhanging presence suddenly seems within inches of Harry’s heart, and the feeling is terrifying. Harry fills the silence, just to make his heart start beating again. “But then Voldemort will be destroyed once and for all?” he asks. For a moment, Dumbledore seems hesitant to answer; Harry begins to feel his legs begin to shake. “We must find the other Horcruxes and destroy them, first, Harry. But, once we have accomplished that, then, yes, it will be possible to destroy Voldemort once and for all.” The lie is far easier to voice than the truth, which is that once Harry is gone, it will still remain for someone to take Voldemort’s life. Even without his Horcruxes, that not be easy to accomplish. “Is there any chance I can survive, Professor?” “There’s always hope, Harry. That, and the wonderful magic your mother conjured on your behalf. And one other thing; the prophecy said, ‘…neither can survive, while the other lives…’ But, you have both survived and lived, and for five years now. By itself, that suggests the prophecy is not as binding as Voldemort must think. And now, you share the same blood. “Should the time come, that blood bond may yet play a role, of which we don’t yet know. So, yes, Harry… there is a chance.” Harry accepts this with relief; there is at least a possibility. “It’s all right, Professor. I suppose my life has always been cursed anyway. If we can finally destroy Voldemort, I guess that will be something.”
But, I guess some of us believe Harry couldn’t know he might survive, or none of this would work. Because he couldn’t be self-sacrificing if he believed he was going to survive.