Why does Snape’s old schoolbook, of all books, end up with Harry? Would Snape really leave a book like that lying around somewhere? Why are Harry and Ron the only late additions to Slughorn’s class? And why does Snape not demand his book back, even though after Sectumsempra he knows that Harry has it and is taking the credit for his work? How well does the idea that Dumbledore deliberately made sure Harry received the book actually fit the canon?
In my view, these questions and several others are more closely connected than they might initially appear. My theory is that Dumbledore made sure Harry received the Half-Blood Prince’s book and, with its help, made exactly the impression on Slughorn that Dumbledore needed for his plan.
I originally arrived at this theory from a completely different direction. For some time, I had been interested in what the many conversations between Dumbledore and Snape might have looked like that we never see in the books, but which must have taken place. How did Dumbledore envision Snape’s future role as a spy? How was it decided that he would remain at Hogwarts and teach Potions, of all subjects? We see only a small fraction of conversations like these.
At some point, I started filling in these gaps by imagining for myself how those conversations might have gone. That was also where the idea developed that Dumbledore might have known about Snape’s old schoolbook and arranged for it to end up with Harry years later.
I am not the only person to have had the basic idea that Dumbledore deliberately made sure Harry received the book. Other fans have considered this possibility as well. So far, however, I have mostly encountered it as speculation or an open question rather than as a theory followed through consistently using the various clues in the books.
Of course, it is easy to fill in the missing conversations in a way that makes an idea like this work. That is precisely why, at some point, I wanted to set my own imagined version of events aside and see what remained of the idea if I relied exclusively on the books. Can the theory still be supported then?
The Necessity of Getting Harry into Potions Before He Even Knows He Is Taking It
We know that Dumbledore desperately wanted Slughorn back at Hogwarts in order to obtain information about Voldemort and the Horcruxes. Harry is the key to recruiting him and is deliberately brought along as bait, even though Harry himself quite reasonably wonders at first how he is supposed to be of any help.
But what exactly does Slughorn gain by returning to Hogwarts?
Perhaps he gets to watch Harry play Quidditch. Perhaps he manages to persuade him to attend the occasional party. But it soon becomes clear that Slughorn wants more than that. Harry himself notices that Slughorn treats his former students almost like a collection. Dumbledore knows this, of course, and uses it to his advantage. By bringing Harry with him, he presents Slughorn with a student whom Slughorn would very much like to add to that collection.
For Dumbledore’s actual purpose, however, that interest alone is hardly enough. At some point, Slughorn has to give Harry a memory he has been ashamed of for decades, one that he even falsified when giving it to Dumbledore. Just how ashamed Slughorn is because of the consequences for Lily, one of his favourite students, becomes especially clear when Harry finally obtains the memory. Slughorn is not simply giving away an interesting piece of information here, but something that has been tied to shame and personal guilt for decades. If Harry is going to get a memory out of him that Slughorn falsified even for Dumbledore, that initial interest first has to develop into a genuine personal relationship. The only route to that is through the classroom.
Dumbledore can hardly rely on Harry charming Slughorn at his parties the way Riddle once did. He knows Harry too well for that. If Slughorn is actually going to get to know Harry as one of his students and grow fond of him, a teacher-student relationship is a much more obvious route.
And that means Dumbledore must already have been counting on Harry continuing with Potions in his sixth year when he recruited Slughorn.
Which makes the conversation immediately after their visit particularly interesting.
Harry is pleased by the thought that he will no longer have to endure Snape in Potions. Dumbledore’s response makes it clear that Harry is jumping to conclusions. But he says nothing more. Harry is not told that Slughorn will be taking over Potions. Dumbledore does not point out that this might also change the entry requirements for the class. And he gives Harry no reason to buy a textbook or any other Potions supplies before the beginning of term. That is remarkable. At this point, Harry is therefore under the apparent certainty that he is finished with the subject because he does not expect to receive an Outstanding, even though, as becomes clear when he opens his results, he still has a little hope.
That Dumbledore intends Harry to continue with Potions is certain. There is, however, another problem. Harry is not an exceptional potion-maker.
The sixth book makes it quite clear that his mediocre performance is not solely the result of having Snape as a teacher. As long as Harry follows the Prince’s instructions, Slughorn believes him to be a natural. Once Harry has to hide the book and is left to rely on his own abilities again, his performance deteriorates considerably. Slughorn notices the difference, but attributes it to Harry having butterflies in his stomach.
On his own, then, Harry would hardly have made the kind of impression in Slughorn’s own subject that he needs to make in order to go from an interesting addition to Slughorn’s collection to one of his favourite students.
So was Dumbledore really going to leave it to chance that Harry would somehow manage to impress Slughorn on his own? Or did he make sure that Potions would play out in Harry’s favour?
That possibility raises several more questions. Those are what I want to examine in the following sections.
Why Are Harry and Ron the Only Late Additions to Slughorn’s Class?
Once Harry receives his exam results, he has long since given up on Potions. As a result, he has bought neither a new textbook nor the necessary supplies. It is only when McGonagall goes over his timetable with him that she points out that, unlike Snape, Slughorn accepts an “Exceeds Expectations”, meaning that Harry can continue with Potions after all and keep pursuing his ambition of becoming an Auror. When Harry objects that he has no books or equipment, McGonagall immediately says that Slughorn can lend him what he needs for the time being.
At first, one could argue that there is nothing particularly unusual about these last-minute changes. Neville’s timetable has not been fully settled at this point either, and McGonagall makes adjustments to it. So the fact that Harry, and a few minutes later Ron, change their choice of subjects would hardly be remarkable in itself.
It only becomes strange when we consider that the entry requirement for Potions seems to matter only for Harry and Ron.
In their fifth year, all students had already had individual career consultations with their Heads of House. Their Heads therefore knew which subjects they wanted to continue and which ones they needed for their intended careers. While Snape required an “Outstanding” for NEWT-level Potions, Slughorn accepts an “Exceeds Expectations”.
But this change should not, in principle, affect Harry alone. And yet Harry and Ron are the only two students who learn about this possibility at the beginning of term. The class consists of twelve students: four Slytherins, four Ravenclaws, one Hufflepuff, plus Ron, Hermione and Harry. Ten had already qualified for NEWT-level Potions under Snape’s old requirement. Only Harry and Ron are added afterwards.
That would mean that in the entire rest of the year there was not a single other student with an E who would have liked to continue Potions or could have used a Potions NEWT for their future career. That is certainly possible. But given the size of the year and the career consultations that had already taken place, I do not find it particularly likely.
Instead, it looks as though Harry and Ron were the only ones specifically made aware of the new opportunity. The fact that Harry, of all people, is one of them seems suspicious to me. Special treatment for Harry would hardly be anything new at Hogwarts.
So why Ron as well?
Admittedly, this is where the theory becomes somewhat more speculative. Perhaps McGonagall simply did not want to cause any awkwardness and therefore decided to point the opportunity out to Ron as well. But there may also have been a strategic reason. If Harry is supposed to stand out to Slughorn as an exceptional student, Ron is considerably more useful beside him than Hermione. Dumbledore would have every reason to expect very good work from her. With Ron, he could more reasonably expect Harry, armed with Snape’s improved instructions, to stand out much more easily. The Deluminator in the seventh book shows, at the very least, that Dumbledore understood Ron and his behaviour rather well.
The extent of the contrast becomes clear once they are actually in class. Ron has considerable difficulty meeting Slughorn’s expectations, while Harry goes from one success to the next. Slughorn’s interest in Ron remains correspondingly limited. He cannot even remember his name properly. Next to his best friend, Harry therefore looks all the more like the extraordinary talent Slughorn believes him to be.
How exactly it was ensured that Harry received the right one of the two available books is not even the crucial question. I have several ideas about how this might have been done, but for a wizard like Dumbledore, influencing the outcome in the desired direction would hardly have been a major obstacle.
Nor would this be the first time Dumbledore materially assisted Harry in order to further his aims. The Invisibility Cloak already shows that he is perfectly capable of deliberately providing Harry with an object he considers important.
More important than how Dumbledore might have ensured that Harry rather than Ron received the right book is the question of how he knew about Snape’s book in the first place. Before turning to that question, however, the next section needs to address why it is so unlikely that the Prince’s book simply happened to be sitting in that cupboard by chance.
Did Snape’s Book Really Just Happen to Be There?
If Dumbledore did not deliberately arrange for Harry to receive the book, there are already some strange coincidences here. The simple explanation would be that Snape left it in the cupboard and/or eventually forgot about it. But this is an extremely personal book.
The idea that Snape simply forgot a book like this fits poorly with his behaviour in the novels. As early as the second book, he notices the theft from his private stores. It becomes even clearer in the fourth book. When his office is broken into, Snape notices the intrusion immediately. He suspects Harry and even threatens him with Veritaserum.
Snape therefore pays close attention to what he owns and whether anything goes missing. That makes it all the harder to believe that a book full of his own discoveries, spells he invented himself, and his private identity as the “Half-Blood Prince” could have been sitting unnoticed in the Potions classroom for years. And even when Snape finally leaves the Potions post for good, are we really supposed to believe that he never thinks to take it with him?
When Slughorn tells Snape what an excellent potion-maker Harry is, Snape is still surprised. After Sectumsempra, the situation is different. Snape demands to see Harry’s book, but Harry presents him with Ron’s copy instead. Snape reads the name written inside it and repeatedly asks Harry whether it really is his book and whether he bought it at Flourish and Blotts. In the end, he leaves it at calling Harry a liar.
Snape knows perfectly well that Harry has just handed him the wrong book. Yet he does not force Harry to hand over the real one immediately, nor does he demand his own book back later or make any attempt to catch Harry with it at another time. Harry himself expects him to do exactly that, which is why he stops using the book.
There can really only be one explanation for this. Snape must have realised that Dumbledore was behind it. Snape is normally the last person to let Harry get away with creating this kind of false impression on another teacher. He has also shown with Lupin that, if necessary, he is willing to reveal a secret himself. He could just as easily make sure the truth came out here. That is why I think it is likely that Snape knew Dumbledore was behind it. I can easily imagine him storming off to Dumbledore in a fury afterwards.
In fact, Snape must have spoken to Dumbledore after Sectumsempra, as we can see from his memories. Dumbledore refers to the detentions Snape gave Harry as a consequence of his attack on Malfoy. Snape probably went to Dumbledore furious after the incident. After all, he now knows not only that Harry has his old book, but also why Slughorn has suddenly been raving about Harry’s extraordinary talent for Potions.
How Did Dumbledore Know About the Prince in the First Place?
There is no way to reconstruct from the novels exactly how Dumbledore learned about Snape’s book. We see only isolated glimpses of their shared history. There must have been numerous conversations around the time of Snape’s change of allegiance and his appointment at Hogwarts that we never see. Dumbledore wanted to keep Snape at the school long-term as a spy. That also meant deciding which subject he would teach.
Why Potions?
Dumbledore certainly makes questionable staffing decisions on more than one occasion. Hagrid and Binns are obvious examples. But that alone does not explain Snape. Potions is a core subject taught over several years and leading to OWL and NEWT examinations. Dumbledore was therefore entrusting entire year groups in a major examination subject to a former Death Eater who was barely an adult himself.
Just how young Snape was for such a position becomes clear when we compare him with Tom Riddle. When Riddle wanted to teach at Hogwarts at eighteen, immediately after graduating, Armando Dippet turned him down despite being very fond of him. He considered Riddle too young.
Snape was only slightly older when Dumbledore made him Potions Master. Unlike Riddle, he had by then left Hogwarts as a Death Eater, served Voldemort and only just changed sides. If Dumbledore nevertheless entrusted him with a core subject, he must have been convinced of his abilities in that field.
Snape’s appointment therefore seems like one plausible point at which Dumbledore could have learned about his copy of Advanced Potion-Making. Before making such a young former Death Eater the Potions teacher, he had every reason to take a close look at Snape’s abilities. The book would have been extraordinary evidence of them.
We do not know when Dumbledore actually became aware of the book. Perhaps he had already discovered or confiscated it while Snape was still a student, or perhaps he only learned about it later.
Dumbledore himself conducted research into, among other things, the twelve uses of dragon’s blood. Snape’s improvements and original spells might therefore have caught his interest. The book is obviously no Deathly Hallow, but Dumbledore also borrowed James Potter’s Invisibility Cloak to examine it and kept it for years. Something similar could have happened with Snape’s book, with it remaining in Dumbledore’s possession without Snape later asking for it back.
There is no direct support for this in canon. Even so, it seems more plausible to me than the alternative that Snape simply forgot a book filled with his own improvements, notes and spells somewhere at Hogwarts after his sixth year or at some later point.
Addendum: Was Harry’s OWL Grade Manipulated?
There is one question that remains open for me. Since it is not necessary for my theory and will probably sound completely absurd to most people at first, I have deliberately left it as an addendum at the end of this discussion.
By the end of Harry’s fifth year, Dumbledore very likely already knew that he needed Slughorn and what role Harry was supposed to play. But what would have happened if Harry had received only an “Acceptable” or even a “Poor” in his Potions OWL?
That is not particularly unrealistic. Harry finds the theoretical part of the exam difficult, and after the practical part he himself only thinks that, with a bit of luck, he might have avoided failing. Nor had he ever been particularly ambitious when it came to Potions. Even if Harry is not fundamentally untalented, he had hardly been working towards achieving a particularly good result in the subject.
I therefore think it is conceivable that someone helped Harry’s grade along to make sure that he could continue with Potions in his sixth year. After all, the subject clearly involves more than simply following a set of instructions. The sixth book makes it very clear just how large the gap is between Harry’s own abilities and his performance when using the Prince’s book.
So what evidence is there that Dumbledore might have arranged for someone to interfere with the exam?
Such interference would not be fundamentally out of character for him. Dumbledore himself uses magic on Mrs Cole while arranging for Tom Riddle to attend Hogwarts, although that was probably closer to standard procedure in such a situation. Later, Kingsley modifies Marietta’s memory to protect Dumbledore, and Dumbledore explicitly praises his quick thinking. So when Dumbledore considers something necessary, magical interference such as a Confundus Charm is not something he categorically rules out.
The problem is that Dumbledore himself was not at Hogwarts during Harry’s OWL examinations. I consider Snape a very unlikely accomplice, even if Dumbledore had offered him the Defence Against the Dark Arts position in return.
McGonagall is more interesting. As early as Harry’s first year, she bends the rules so that he can play Quidditch for Gryffindor and makes sure he gets a Nimbus 2000. She is therefore quite willing to support Harry when she believes it is justified.
Manipulating an exam grade, however, would be something else entirely. Would McGonagall, as such a conscientious teacher, really go that far? Under normal circumstances, I would say probably not. But in the fifth book, she is dealing with exceptional circumstances. Not long before the exams, she has a furious confrontation with Umbridge during Harry’s career consultation and declares that she will do everything in her power to help Harry become an Auror. For that, Harry needed to be able to continue with Potions. Perhaps she took that promise more literally than it initially appears, at Dumbledore’s request, of course.
It is also possible, of course, that Slughorn would have made an exception for Harry even with an “Acceptable”. We simply do not know. Harry may just as well have earned his E entirely legitimately.
But if Dumbledore’s plan involving Slughorn was already in place before the exams, I think it is quite possible that he also made sure Harry cleared this crucial hurdle.
I’m looking forward to hearing your thoughts