“After an interval of some years, however, [Voldemort] used Nagini to kill an old Muggle man, and it might then have occurred to him to turn her into his last Horcrux.”

Dumbledore’s comment to Harry could be understood the way you have stated. But I really think it isn’t a direct statement meaning this happened and then that happened. All I think Dumbledore is stating is that it wasn’t a planned murder / horcrux.

Is it possible my ideas are wrong, of course.

About Lily’s sacrificial death, it didn’t turn her baby into a horcrux. It saved his life. It protected him. It is because of her sacrifice, that I believe the horcrux did not do what it was intended to do, encasing itself in the body of Harry. The horcrux remained on the outer part of Harry, his skin.

Slughorn is not the only person from whom we learned something about Horcrux making. Slughorn didn’t know the spell to use, but the point I made in the essay is that Dumbledore clearly does. He had to learn everything he could about Horcrux-making because he needed to know what all the possibilities were and about any special information he needed to know in order to destroy them.

He told Harry, “After an interval of some years, however, [Voldemort] used Nagini to kill an old Muggle man, and it might then have occurred to him to turn her into his last Horcrux.”

We got a lot more information from that statement than we did from Slughorn. Dumbledore surmised that Voldemort had used Nagini to kill Frank Bryce and the decision to turn the snake into a Horcrux was an afterthought. So we learned: 1) the murder is what counts, not the method used to kill (killing curse, lethal poison, etc.), 2) it doesn’t matter whether the murderer killed directly or used a proxy he was controlling (Slytherin’s basilisk, Nagini), 3) the murderer doesn’t even need to be considering making a Horcrux at the time of the murder to be able to make a Horcrux from that murder later on, and 4) the murder comes before the Horcrux is made rather than being an internal part of the Horcrux-making process.

And that is logical given what Slughorn had already said and given that it’s highly probable that Riddle made the ring Horcrux from the Riddle triple homicide months after they were killed. Dumbledore didn’t know of any murders that Voldemort had committed between the Riddle murders and Hepzibah Smith’s poisoning.

So for me, speculations that Voldemort needed to peform a spell before killing Harry require so many things to be completely undermined, particularly information we got from Dumbledore. And as Rowling said (I know I’m a broken record), Dumbledore’s guesses are never very far wide of the mark.

And there is still the ultimate thematic problem. A Horcrux is the wickedest of magical inventions, and to accept Harrycrux and Scarcrux theories, you have to believe that Lily’s sacrificial death turned her baby into one. I don’t buy it, and there is too much canon evidence IMO to explain Harry’s Parseltongue and mental connection with Voldemort without resorting to Harrycrux and Scarcrux theories.

Where & when did Tom Riddle learn to make horcruxes?
Your point on Tom already knowing how to make a horcrux before he spoke to Slughorn is possible. I have just reread the scene and it isn’t a certainty though, there is room for the possibility that Tom didn’t yet know the spell to create a horcrux. Tom just seemed so eager asking “Encase? But how?” [HBP 23, pg 498]. Tom Riddle finding a book with some information on horcruxes in the Room of Requirement is an interesting assertion, and I can see that as well. I too wondered where Tom learned how to make horcruxes, but my thoughts lead me down another road, the road to Knockturn alley and Borgin and Burkes. Borgin and Burkes of course is a shop devoted to dark arts items, so it seemed reasonable to me that Tom could have gotten the information he needed on horcruxes there. We know that after school he worked there.

Horcrux spell a before or after
In your essay you say “To make a Horcrux, the soul needs to be split first by a supreme act of evil—murder—so that a torn portion could be encased in the object.” — This is not what the text states, though.
Slughorn gives an overview.
“Well, you split your soul, you see, and hide part of it in an object outside the body.” ~Slughorn [hbp 23 pg 497]
“By committing murder. Killing rips the soul apart. The wizard intent upon creating a Horcrux would use the damage to his advantage.”~ Slughorn [hbp 23]
“There is a spell, do not ask me, I don’t know!” ~ Slughorn [hbp23]
I don’t think Slughorn new that much more about horcruxes at the time. He wasn’t the Defense against the dark arts teacher. And it is only an overview, not instructions.

We do not know whether the horcrux spell comes before or after the murder or many details about the horcrux making. We all are reading into what is being said by the characters. I am willing to admit that I don’t know, because I don’t. I just have ideas and thoughts on it. I don’t think that it is possible at this state to exclude the possibility that the horcrux spell is prior to the murder or happens after. My reason for asserting the opinion that the horcrux spell comes first has to do with Voldemort’s merciful ultimatum to Lily the night she died. I never could understand it. Voldemort’s mercy seems to go against everything we know about him. It seemed to me that more then likely Voldemort’s motive wasn’t mercy, but something else. What else would have motivated a cold blooded killer to offer someone who was in the way their life. If the horcrux spell came first and a murder had to immediately follow it, this could explain why Voldemort offered Lily her life. Here’s a scenario Voldemort began the horcrux spell to make his final horcrux; Lily won’t get out of the way, so Voldemort knowing this is his final horcrux murder offer Lily her life, she declines and Voldemort has no choice other then to kill her and make the final horcrux from her murder. Now you may ask where is the proof, the canon, the quotes, well of course there are none, it’s just a way of understanding some events. It’s that simple.

Mind / Powers – the Soul
I know that you are making the point against Harry being a horcrux and that the connection is a connection of the mind and not the soul. I am thinking on it, and you made a valid point about the scar burning, but I’m not there yet.

You did your homework. I’m going to think about this awhile.

I don’t mean to get techinical but when you refer to a mind connection, do you mean the physical brain or just thoughts?

The scar only burns in connection to Voldemort’s mind, not to parts of Voldemort’s soul. So that again is an example of the mind-to-mind link from the scar.

I’m going to have to think over all you’ve said in your most recent post. However I will quickly comment that the idea that Tom already knew how to make horcruxes before speaking with Slughorn is interesting, and I never thought about that. Good point.

I do have a question for you.

When I am think about theories there are certain pieces that must fit into my theories for me to proceed with them. Here is one of the pieces. Harry’s scar burns.

Harry’s scar burns. This seems significant, atleast to me, it has occured in almost ever book. Based on your theory of the mind/powers transfer instead of soul/horcrux tranfer why does Harry’s scar burn?

In the first place, I think we need to acknowledge a major plothole in Goblet of Fire—Why didn’t Fake Moody just portkey Harry to the Riddle House on the first day of school and get the rebirthing ceremony over with? It seems pretty stupid for Voldemort to have waited 10 months in the first place, but that’s what happened.

So while your question about why Voldemort didn’t wait until the rebirthing ceremony to make Harry into a Horcrux is a very good one, my own gut tells me that’s another plothole. And if your argument is that Voldemort wouldn’t have made a Horcrux out of Nagini at the beginning of GoF but would have waited until June at the end of GoF to make one out of Harry’s death, then Dumbledore’s list (cup, locket, Nagini, something of Gryffindor’s or Ravenclaw’s) is all wrong even though Rowling said his guesses are “never very far wide of the mark.”

My point about Voldemort’s vulnerability is that he wanted the magic power of a seven-part soul to get him through a difficult year. That’s why he wanted to make six Horcruxes in the first place–because seven is the most magically powerful number. So in that sense, he felt he was making himself less vulnerable by making the sixth Horcrux out of Nagini. It didn’t have anything to do with Wormtail.

We didn’t see Nagini until GF1. She had gone off to explore the house, and when she returned, she told Voldemort there was an old Muggle man listening in the hallway. I don’t see how that is evidence that he had any unusual control over her. Crookshanks would have done the same thing. The part of my end scene is just something I would like to see happening because it would be a parallel to the end of GoF when Harry’s powers were stronger than Voldemort’s in making the bead of light head for Voldemort’s wand. That light beam had resulted because they were both using wands Fawkes’s feather cores, but even though Harry was an underaged and unqualified 14 year old and Voldemort was back in his full powers, Harry’s powers were stronger. Nagini is the dark counterpart of Fawkes and both Voldemort and Harry have the power (from Slytherin) to speak to her in Parseltongue. My Nagini battle scenario envisons Harry’s ability, through Parseltongue and whatever other powers he has to be able to at the very least throw Nagini into confusion by countering Voldemort’s orders to her. I never said Voldemort would have “supreme” control over Nagini as a Horcrux, nor did Dumbledore.

I think Riddle learned to make Horcruxes from one of the banned books he found in the Room of Requirement. Moaning Myrtle was killed in June 1943 during Riddle’s fifth year, and he made the diary sometime between her death and his next birthday on December 31. Canon says he learned about his family history during that same fifth year, so it seems clear to me that he killed the Riddles and framed Morfin during the summer immediately after he killed Myrtle with the Basilisk.

When I first read the chapter in which Dumbledore and Harry saw Slughorn’s real Horcrux memory, I thought Riddle already knew how to make Horcruxes but was pretending not to know because the subject was banned. His real question was whether he could split his soul into seven parts (Dumbledore told Harry that what he really wanted to know was whether he could split his soul into seven because no book would be able to give him that information). So IMO Riddle had already made the diary Horcrux before he talked to Slughorn. He then made the ring Horcrux after talking to Slughorn.

You can certainly hold a different opinion, but you have to explain how Riddle learned how to make Horcruxes since Slughorn didn’t know and the subject was banned at Hogwarts.

From what we learned from both Slughorn and Dumbledore is that to make a Horcrux, the murder comes first and the Horcrux-making follows. We don’t know more than what they told us, but nothing that either said supports the idea that the murder comes after or that the murder is an internal part of the Horcrux-making. Perhaps it makes sense to you that the spell has to be cast before the murder, but it doesn’t to me, and Dumbledore and Slughorn seem to be saying the opposite.

It was Rowling herself who said the scar is a magical window into Voldemort’s MIND. It was Dumbledore who said Slytherin’s POWERS were transferred into Harry. And it was Dumbledore who distinguished soul on one hand and mind/powers on the other. That’s canon. My examples of the brain in the DoM leaving thought-scars and the Sorting Hat having “brains” are examples to show that that there is no need for Harry to have any part of Voldemort’s soul in him to explain his ability to speak Parseltongue or the mind-to-mind connection he has with Voldemort through the scar.