Happy birthday, Severus Snape!
We don’t know the exact January date that Dumbledore told him he’d have to teach Harry Occlumency, but it would certainly be typical of this character’s luck if it happened on his birthday, wouldn’t it?
Let’s take a look at those lessons and see what was going on in Snape’s mind at the time.
The Occlumency passages are among Rowling’s most masterful chapters: dense, tricky to interpret, confident and intentional. She wrote them carefully to plant doubts about Snape’s motivations and leave them wide open. Is he, as Ron and Harry suspect, trying to make Harry more vulnerable to Voldemort in each lesson? Is he trying to appear to be making Harry more vulnerable, in order to fool Voldemort, while simultaneously trying to teach Harry Occlumency? Is he sabotaging the lessons because he hates Harry? Is he taking out a 20-year grudge on a vulnerable kid?
Most of all, when he ordered Harry to clear his mind of emotion, why didn’t he explain how?
Surprisingly, the truth might be the simplest answer:
Snape was trying to teach Harry in good faith but had to stop when the risks became too great.
A close consideration of the Occlumency lessons shows us the clues.
1. Time and distance matter in magic. Why does Rowling emphasize this at the beginning of the lessons? Until now, Voldemort hasn’t been able to spy directly on Snape’s doings within Hogwarts, except for the year he was in Quirrell’s head. But now that Voldemort has Harry’s blood and can see through Harry’s eyes, he can bypass all of the magical protections keeping him out of Hogwarts. Snape now must assume that Voldemort might be watching and evaluating him.
2. Voldemort really is a great Legilimens. And Snape is, as far as we know, the only person among Harry’s allies with proven, repeated success in Occluding Voldemort. If Dumbledore can’t teach Harry, it has to be Snape.
3. Snape tells Harry nothing is off-limits. He says, “You may use your wand to attempt to disarm me, or defend yourself in any other way you can think of” (OotP 534). Sounds fake, doesn’t it? Is it really safe to take Snape at his word about this? But evidently, he means it. He doesn’t get angry when Harry hurts him with a painful Stinging Hex. He doesn’t get defensive when Harry sees his vulnerable childhood memories. He doesn’t even retaliate when Harry says rudely that it’s Snape’s job to spy on Voldemort. He actually acknowledges that Harry is right.
4. Snape actually praises Harry for doing well. “Well, for a first attempt that was not as poor as it might have been” (OotP 535) is the only time Snape ever manages to choke out any credit to Harry. Harry must have really impressed him.
5. He tells Harry not to say the Dark Lord’s name. Harry asks why — and Snape’s answer is interrupted. That tells the reader that this question is significant. We learn in Deathly Hallows, with the Taboo and also with the Deluminator, that saying the name of a magical person is a sort of spell and might draw their attention. Best to use euphemisms if trying to avoid notice.
6. Whenever Harry’s scar prickles during these lessons, that means Voldemort is aware and watching. Harry notes that “his scar hardly ever stopped prickling […] and he was sure he could date this increased sensitivity firmly from his first Occlumency lesson with Snape” (OotP 553-4). If we check the first moment that Harry’s scar prickles during these lessons, it happens when Harry has the “blinding realization” that he knows the door from his dreams (OotP 537). Voldemort and Harry can each sense when the other has a jolt of emotion. Harry’s surge of understanding has alerted Voldemort, who now knows that Harry is currently in a private lesson with Snape.
7. Snape also has a magical scar: his Dark Mark. We know from Goblet of Fire that Dark Marks are sensitive to fluctuations in Voldemort’s mood. Harry can feel it when Voldemort has extremes of emotion. At the same time, so can anyone with a Dark Mark. This was why, when Harry made the connection about the mysterious door and “his scar was prickling unpleasantly,” Snape also sensed Voldemort’s awareness and “lifted the spell before Harry had even tried to fight back” (OotP 536-7).
8. Snape shuts down in the lessons and acts cold and nonchalant, once he senses that Voldemort is watching. After this moment, the agitated Snape first loses control and scolds Harry not to say the Dark Lord’s name, then collects himself “as though he was trying to appear cool and unconcerned” (OotP 537) and ends the lesson abruptly.
9. If Snape tells Harry how to make his mind blank, Voldemort will know.
This is the crux of it. Before Voldemort checked in, the lesson was going well, following a structure similar to Harry’s private Patronus lessons with Lupin. Snape, like Lupin, first let Harry demonstrate what he could do without any training and praised the surprisingly strong results. He praised Harry for achieving Occlumency when Snape saw the memory of kissing Cho. He instructed Harry to clear his mind of emotion and try again, although Snape lost composure after seeing Harry’s yearning vision of his parents and snarled unhelpfully at Harry for wearing his heart on his sleeve. Immediately after, Harry recognized the door in his visions. Voldemort started paying attention and Snape could not possibly spell out, in front of Voldemort, the secret to how Snape has successfully Occluded Voldemort all this time.
If the lessons had been private from Voldemort, Snape could have gone back to the moment that Harry had protective feelings about Cho and built on that to show Harry that the desire to protect loved ones is the foundation of Occlumency. This would have been similar to Lupin’s process of having Harry repeat attempts at a Patronus until he could hit upon the kind of memory that would bring him the most strength: happiness based on connection with others rather than, say, his first time on a broom (PoA 238).
But there is no way for Snape to train Harry in this method without Voldemort learning how Snape manages to Occlude him. It will be another two years before Harry develops it on his own while burying Dobby: “He had learned control at last, learned to shut his mind to Voldemort, the very thing Dumbledore had wanted him to learn from Snape. […] Grief, it seemed, drove Voldemort out…though Dumbledore, of course, would have said that it was love….” (DH 478) It is painful and grim that Harry doesn’t have more consistent guidance in learning this skill — but this is not unrealistic for a story about an orphan of war.
10. Snape and Harry begin to empathize with one another. Grudgingly, uncomfortably, Snape and Harry begin to realize through the Occlumency lessons that they can identify with each other’s childhoods. Snape understands how Harry felt when Aunt Marge’s dog chased him; Harry understands how Snape felt when the Marauders attacked him. Snape realizes that Harry wasn’t exactly raised as a pampered prince, and Harry realizes that Snape hadn’t been lying about James’s arrogance.
The memory that Harry saw in the Pensieve, of Snape being bullied and then calling Lily a slur, showed nothing that would surprise Voldemort. But we find out in “The Prince’s Tale” that the other two memories that Snape put in the Pensieve were about Snape switching allegiance to Dumbledore. That’s what Voldemort would have seen through Harry’s eyes if Snape hadn’t stopped Harry. And even if Harry never saw the other two memories, there’s no telling how Harry — who has his mother’s eyes, and can see and understand things about Snape’s feelings — would eventually put together the feelings in Snape’s Worst Memory with his growing understanding of this unpleasant teacher as a fellow human being. Voldemort doesn’t understand what he sees of Snape through his own Legilimency, but if he sees Snape through Harry’s eyes, his understanding will be different. Snape has got to put a stop to these Occlumency lessons. If Voldemort sees that his spy is a double agent, the results will be fatal to Snape and disastrous to Dumbledore’s efforts.
Happy birthday, Severus Snape. The tasks you were given were not only thankless but impossible. But we see you.