Why didn't the soul inside Voldemort's body die when he tried to kill Harry?

Question

In Deathly Hallows, Dumbledore says,

"...the Killing Curse rebounded on Lord Voldemort, and a fragment of Lord Voldemort's soul was blasted apart from the whole, and latched itself onto the only living soul left..."

We know that Voldemort was hit with a Killing Curse. We know that some of his soul survived this and attached itself to Harry. We also know that some other part of Voldemort's soul, which was not contained inside Harry or in any of his Horcruxes, went off to Albania and then ended up in Little Hangleton. How did either of these pieces of soul survive the Killing Curse?

Answer 1

“I miscalculated, my friends, I admit it. My curse was deflected by the woman’s foolish sacrifice, and it rebounded upon myself. Aaah... pain beyond pain, my friends; nothing could have prepared me for it. I was ripped from my body, I was less than spirit, less than the meanest ghost... but still, I was alive. What I was, even I do not know... I, who have gone further than anybody along the path that leads to immortality. You know my goal - to conquer death. And now, I was tested, and it appeared that one or more of my experiments had worked... for I had not been killed, though the curse should have done it. Nevertheless, I was as powerless as the weakest creature alive, and without the means to help myself... for I had no body, and every spell that might have helped me required the use of a wand...

_{^{Harry Potter and the Goblet of Fire, Chapter 33, The Death Eaters}}

His Horcruxes saved him. As Slughorn explains below.

“I don’t quite understand how that works, though, sir,” said Riddle.

His voice was carefully controlled, but Harry could sense his excitement.

“Well, you split your soul, you see,” said Slughorn, “and hide part of it in an object outside the body. Then, even if one’s body is attacked or destroyed, one cannot die, for part of the soul remains earthbound and undamaged. But of course, existence in such a form...”

_{^{Harry Potter and the Half-Blood Prince, Chapter 23, Horcruxes}}

Answer 2

While the other answers are correct in showing why Voldemort didn't die, I think they're missing a key point in your question - namely, why the soul fragments were unharmed after being hit with the Killing Curse.

The answer is...Avada Kedavra doesn't harm souls!

The series implies that your soul is the part that "moves on" after death. As such, it cannot be harmed by any known means, except one. The only instance of soul damage in the HP series is the described by Slughorn as "the supreme act of evil"...killing. Even then, this doesn't destroy your soul, it splits it. Whether or not the torn piece withers and dies, or moves on without you is an interesting question in itself (assuming you don't create a Horcrux with it).

Avada Kedavra is an interesting piece of magic in that it seems to target neither the body nor soul, but the link between them. The victims have no visible damage at all, but nor are they forbidden from moving on. We have at least one concrete example of this - after Harry is killed, you'll note that Voldemorts soul fragment (never mind Harry's!) has not been destroyed by Avada Kedavra. It has instead been moved on to Limbo.

So, regardless of the Horcruxes, Voldemorts (already damaged) soul wouldn't have been harmed by Avada Kedavra. It was, however, his Horcuxes that stopped his disembodied soul fragments from moving on.

Answer 3

I think you are misunderstanding how a Horcrux works. The part of the soul held in a Horcrux doesn't replace the rest of your soul if you are killed - while Slughorn's description is vague, if it worked that way, then at least one of Voldemort's Horcrux's would not have still contained a fragment of soul after he was first killed.

Instead, the fragment of soul in the Horcrux anchors the rest of the soul to the mortal world, preventing it from moving onwards, so, as Dumbledore pointed out, it was still necessary to kill Voldemort's recreated body as well as to destroy every Horcrux in order to finally defeat him.

Answer 4

His Horcruxes tied his main soul to life.

When the Dark Lord’s Killing Curse rebounded on him, it both ripped his soul from his body as his body was killed and fractured a piece off of his main soul, which went on to live in Harry.

“Tell him that on the night Lord Voldemort tried to kill him, when Lily cast her own life between them as a shield, the Killing Curse rebounded upon Lord Voldemort, and a fragment of Voldemort’s soul was blasted apart from the whole, and latched itself on to the only living soul left in that collapsing building.”
_{^{- Harry Potter and the Deathly Hallows, Chapter 33 (The Prince’s Tale)}}

When the Killing Curse rebounded, his Horcruxes worked as they were meant to - they tied his main soul to life by keeping part of his soul outside his body, ensuring it couldn’t die even if his body was killed.

“Well, you split your soul, you see,’ said Slughorn, ‘and hide part of it in an object outside the body. Then, even if one’s body is attacked or destroyed, one cannot die, for part of the soul remains earthbound and undamaged. But, of course, existence in such a form …”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 23 (Horcruxes)}}

When his soul split, both pieces were tied to life, as up until the moment of the split, they were both part of the main soul that the Horcruxes tied to life. The piece that fractured off was still part of the main soul until it had split, so it was also tied to life by the Horcruxes then. It of course lost that protection after it was no longer a part of the main soul, but it was a part of it at the time it split, allowing it to live and attach to Harry.