How we cite our quotes: All quotations are from Harry Potter and the Half-Blood Prince.
Quote #1
BELLATRIX: Cissy, you can't do this! He can't be trusted.
NARCISSA: The Dark Lord trusts him.
BELLATRIX: The Dark Lord is mistaken.
Here, Bellatrix and her sister are talking about Snape. Dumbledore thinks Snape is working for him, and the Dark Lord does, too. Only Snape knows who's getting zoomed.
Quote #2
SNAPE: As it so happens, I'm aware of your situation, Narcissa.
BELLATRIX: You? The Dark Lord told you?
SNAPE: Your sister doubts me. Understandable. Over the years, I've played my part well. So well, I've deceived one of the greatest wizards of all time. [Bellatrix makes scoffing noises.] Dumbledore is a great wizard. Only a fool would question it.
NARCISSA: I don't doubt you, Severus.
Bellatrix and Narcissa are at opposite of ends of the "Is Snape loyal?" debate. Bella doesn't trust him for a second, but Cissy seems to believe Snape.
Snape himself doesn't seem to mind that the sisters are airing the elephant in the room, and assures them he's been pretending with Dumbledore, not the Dark Lord.
Quote #3
HERMIONE: You really shouldn't have done it.
HARRY: I know. I suppose I could have just used a Confundus charm.
HERMIONE: That was different. That was tryouts. This was an actual game. [Harry takes the full vial of Felix Felicis out of his pocket and shows it to her.] You didn't put it in. [Harry shakes his head.] Ron only thought you did. [Harry nods.]
And now, for a completely different form of deception: Harry let Ron think that he'd slipped him a lucky potion to make him awesome at Quidditch. He hadn't really given the potion to Ron, but the trick made Ron confident enough to actually be awesome at Quidditch. We'd say this is pretty much the best kind of lie, no?
Quote #4
DUMBLEDORE: Thievery is not tolerated at Hogwarts, Tom. At Hogwarts, you'll be taught not only how to use magic, but how to control it.
Well, looks like Voldemort was dishonest from the start—like, even when he was a young, innocent-looking kid. When Dumbledore went to visit him at the orphanage, he detected a stolen item in Tom's closet. Dumbledore seemed to want to give Tom a fresh start at Hogwarts, but as we all know, that…didn't exactly work out.
Quote #5
SLUGHORN: I beg your pardon? I don't know anything about such things and if I did, I wouldn't tell you. Now, get out of here at once, and don't let me ever catch you mentioning it again!
This moment occurs in a memory of Slughorn's—a memory that's been altered. In this version of Slughorn's history, he is totally refusing to talk to Voldemort about some dark magicky stuff that the young Dark Lord came across in the restricted section of the library. We're guessing the true version of the memory is a lot different, because otherwise, why would Slughorn have doctored it?
Quote #6
DUMBLEDORE: Confused? I'd be surprised if you weren't.
HARRY: Well, I don't understand. What happened?
DUMBLEDORE: This is perhaps the most important memory I've collected. It is also a lie. This memory has been tampered with by the same person whose memory it is. Our old friend, Professor Slughorn.
HARRY: But why would he tamper with his own memory?
DUMBLEDORE: I suspect he's ashamed of it.
HARRY: Why?
DUMBLEDORE: Why, indeed? I asked you to get to know Professor Slughorn and you have done so. Now I want you to persuade him to divulge his true memory. Any way you can.
HARRY: I don't know him that well, sir.
DUMBLEDORE: This memory is everything. Without it, we are blind. Without it, we leave the fate of our world to chance. You have no choice. You must not fail.
Gulp. Harry and Dumbledore have just viewed Slughorn's tampered-with memory, and now Harry has been tasked with getting the real story from Slughorn. "Any way you can." Sounds like maybe Harry could end up getting involved in some deception himself.
Quote #7
HARRY: I'm going to tell you something. Something others have only guessed at. It's true. I am the Chosen One. Only I can destroy him, but in order to do so, I need to know what Tom Riddle asked you all those years ago in your office, and I need to know what you told him.
Okay. Here, Harry is actually being honest with Slughorn (to get what he wants, of course). Normally Harry doesn't make it a habit to go around advertising that he's the Chosen One, but since he knows it'll get Sluggy chatting, he lets the cat out of the bag.
Quote #8
SLUGHORN: Please, don't think badly of me when you see it. You've no idea what he was like, even then.
This is it: Slughorn is finally going to tell the truth about what happened with Voldemort all those years ago. We're not sure if he's really telling the truth about not knowing Voldemort's true nature, but we'll let that go, since he's at least giving Harry the real memory. And with all the deceit and lying going on, we really needed a moment of truth. Phew.