Question about Pensieve memories

[Carol]

No: HPFGUIDX 186024

Mindi wrote:
> 
> I wonder if they can choose for it to be erased or copied when they extract the memory, kind of like how on a computer you can choose to copy or cut something.
>
Carol responds:
I like that idea. However, Morfin Gaunt and Hokey the House-Elf had no choice in the matter when Tom Riddle somehow tampered with their memories and implanted false ones to make them think they'd committed murder, but the true memory was still there underneath or Dumbledore couldn't have accessed it.

I suspect that he removed the memory from his head, tampered with the point of view so that, for example, Hokey couldn't see his hands and know they weren't hers, and then somehow placed it in their heads. But he must have retained the real memory. Otherwise, he wouldn't know that he'd killed his "filthy Muggle father" (and grandparents). He'd certainly remember planning the murders even if he didn't remember carrying them out, but I suspect that, as you put it, he copied and pasted the slightly altered memories and retained the unaltered ones. (Quite a feat for a sixteen-year-old Dark wizard!)

Something similar must have happened with Slughorn, who removed the memory and tampered with it, but the real memory was still there as DD knew or he wouldn't have asked Harry to obtain it.

As for Snape, he didn't want Harry to accidentally Legilimens certain memories (presumably through Protego), so he took the precaution of placing them in the Pensieve (cut and paste?). I suspect that he still remembered which memories they were and that such things had happened; he just couldn't recall the details. (Heck, I can't recall the details of the vast majority of things that have happened to me. People who claim to recall detailed conversations from their past are, IMO, seriously mistaken. Memories really aren't crystal clear and objectively real as they appear in a Pensieve.) 

Dumbledore, too, would have remembered that certain things happened (Karkaroff's hearing in GoF or the visit to young Tom Riddle in HBP), but he, too, wouldn't remember the details if he'd removed the memory unless he was studying it in the Pensieve, in which case he'd have a secondary memory, a memory of the memory, like Harry's memories of his visits to the Pensieve. In a sense, Hokey's and Morfin's and Bob Ogden's and Snape's and Dumbledore's memories are now his memories, too. And we can throw in Tommy Riddle's diary memory (presumably of the copied-and-pasted variety) as well.

Or a particular memory works the way JKR needs it to work in the plot of a particular book in the sequence. Consistency is not her forte.

Carol, just tossing out random thoughts here