Couldn't he have used his pensieve to find out which of the three was responsible for Ariana's death?

 

Probably, but I think he was too afraid of the answer to try looking.

 

Pensieves in general are one massive plothole, so try not to think too hard on those.

 

If they both shot spells at the same time, and both spells appeared to hit her at the same time, it could be hard to tell, even with the ability to review the situation.

Even harder if she died from some combination of spells rather than just one.

 

I like the reason that he was too scared to check better, though.

 

It's also possible that it was such a shock that he can't remember the exact details clearly. It happened when they were just out of school, so it could have taken decades for him to get access to a pensieve. What you put in the pensieve is what you remember, after all, and the trauma/shock and decades of time's passage could be relevant.

Also assuming that Dumbledore got a pensive around 60 years old, give or take a few decades, it could just be that he doesn't want to open old wounds that he's been carrying for decades. He already blames himself (and Gellert), and could think that Ariana's death was the consequence of them fighting, not whoever cast the spell, or something.

 

The first point doesn't work because:

I checked over the books again, and I think I agree with Red Aviary because Dumbledore himself at one point says that "... It was the truth I feared. You see, I never knew which of us, in that last, horrific fight, had actually cast the curse that killed my sister. You may call me cowardly: You would be right, Harry. I dreaded beyond all things the knowledge that it had been I who brought about her death, not merely through my arrogance and stupidity, but that I actually struck the blow that snuffed out her life.”

Thanks for the help, everyone.

 

Actually, it still does. Notice what she said. "It’s somewhere in your head, which I’m sure it is, in all of our brains. I’m sure if you could access it, things that you don’t know you remember are all in there somewhere."

What it sounds like she's alluding to, is called absolute recall. That every single thing you see, whether you realize it or not, you can recall. Clerith's point, if I understand him correctly, is the trauma could have altered the actual biochemical underpinnings of the memory itself (as emotional trauma has a distinct effect on biochemistry) by which there is no longer a way to pull the original memory. In that case, all you'd get in the Pensieve is the reconstructed memory (similar to, but not purposed like Slughorn's false memory of his discussion with Riddle). If it's the way your saying, then Slughorn couldn't have altered it, because the magic would have fought against it.

But with all that said, I think you're better off iwth the way you're going about it. It was too painful and he didn't want to know.

 

Actually, aren't repressed memories just a bunch of nonsense not proven by any science?

 

It might be more than just absolute recall. After all, in each Pensieve memory we've seen, the spectators enjoy enjoy a somewhat personal experience, as opposed to a "remote viewing", so to speak. Whether the Pensieve randomly interpolates certain things (which would kind of run counter to its purpose) or not, who knows?

 

Don't know, I wasn't referring to repressed memories, but the way our brain processes the information as it happens and as we categorize it, then recategorize it as new information comes in. I guess, repressed memories may fall into that, but it's not what I was thinking at the time.

Edit: from the APA

So, yeah, repressed memories do exist, but they're not common. Still, I was more referring to the above, rather than actual repression.

 

Red Aviary nailed it, as far as I'm concerned. Dumbledore would rather spend his whole life wondering than risk knowing with absolute certainty that he'd directly killed his sister.

Heck, maybe a part of him is also afraid to find out he didn't cast the spell that killed her, considering all the guilt he carries over it. He could be worried that if he found it was Gellert who cast the spell, he'd absolve himself of any guilt over the matter.

 

Or he was simply to stupid to have such a brilliant idea, which is easily possible if you consider his other wrongdoings (e.g. not killing in a terrorist attack aka DeathEater raid)

 

Regardless of the locale, what if someone actually is under the Imperius?
I don't see Dumbledore as being willing to take that risk of murdering innocents.

There's also the wanting to give people a second chance, which I think is because of the whole Grindlewald thing in his youth.

 

I wouldn't be surprised if Dumbledore had made an oath to never kill in the name of the Greater Good again, or something of in that light. It might stray too close to his old ideals for his comfort.

 

I hold it as a bit of headcanon that 'oaths' as we see in fanfic - and other fantasy - aren't a thing in HP. Other than the Unbreakable Vow and Hermione's secrecy paper, there's never much of an indication that these exist or are considered a big deal.

 

Sorry I didn't make it clear. I meant something more along the lines of a Batman-esque oath to himself to never walk down that path again. I hold a similar headcanon, for otherwise, why didn't Voldemort force everyone to swear one to him?

 

Eh, honestly I think that's a bit dumb. Swearing an oath isn't actually as impactful as a person having changed enough that their decisions fall a different way than before.

Besides, do we have any proof whether Dumbledore did or didn't kill people? I've always felt the idea that he never kills was a bit of a strange assumption, I believe he would not actively be attempting to kill people in duels, but I also don't feel that there's any proof that he never killed.