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I didn't find any instance of memory reuse in the Harry Potter books. Once it's in the Pensieve and watched, it's never indicated if it can be taken out again and reviewed.

One counterexample one can use is the first memory of Slughorn, but it could be said from just looking at it that it was tampered with, it was not required to watch it.

Was it possible to reuse memory strands from the Pensieve after watching them? Note that I'm not talking about just storing, but reusing.

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Didn't Dumbledore say at sometime he has been through the memories searching for clues? – Skooba Jan 27 at 19:59
What do you mean by “reusing”? How is reusing different from watching it in the Pensieve? Do you mean whether the same memory can be watched multiple times in the Pensieve? – Janus Bahs Jacquet Jan 28 at 1:17
@JanusBahsJacquet Yes. Snape and Dumbledore are shown storing and watching memories in the Pensieve, but never taking out a strand from the Pensieve back and storing it for reuse later. I was just wondering if that was possible. It seems now that yes, it is. – cst1992 Jan 28 at 5:12
Are your memories reusable? – user32390 Jan 28 at 8:22
up vote 40 down vote accepted


Though it isn't completely clear in the book, I found multiple parts that make it highly likely.

  1. Dumbledore, in THBP, said that he took memories from a house elf and ministry official.

DumbIedore: "I took this memory from her shortly before he died."

  1. Dumbledore most likely saw the memories he took before showing Harry.

  2. This is very clear: Dumbledore told Harry before showing him the messed up memory of Slughorn:

Dumbledore: After we see this, tell me what looks different.

This means that Dumbledore had to have seen it before if he knew that it was messed up and corrupted.

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Yes they are.

In Harry Potter and The Half-blood Prince we see Dumbledore showing Harry a memory

of Slughorn

that Dumbledore himself has already used.

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He may not have; I had thought about that. See the second paragraph. – cst1992 Jan 27 at 7:28
@cst1992 he had. He knew the memory had been tampered with, that's why he took Harry with him on his mission to recruit Slughorn. – ATB Jan 27 at 7:29

Yes. Memories in the pensieve are reusable and capable of being viewed more than once:

In GoF, Harry fell into the Pensieve and Dumbledore's memories witnessing several trials: Igor Karkaroff, Ludo Bagman, and then the Deatheaters that tortured Frank and Alice Longbottom (Neville's parent's). Harry realized that it was a memory and noted the passage of time; so that he experienced not only one memory but several in one sitting. Eventually, Dumbledore joined Harry and removed him from the pensieve, after which Dumbledore proceeded to explain the purpose of the device:

"I use the Pensieve. One simply siphons the excess thoughts from one's mind, pours them into the basin, and examines them at one's leisure. It becomes easier to spot patterns and links, you understand, when they are in this form." -- Goblet of Fire, Chapter 30

Dumbledore also make a comment along the line of having so many thoughts that he finds it necessary to use the pensieve quite often.

Furthermore, it is even possible to alter one's own memories as seen in HBP, when Slughorn modified the memory that he was ashamed of - though Dumbledore said that it was crudely done. And of course, we know that memories can be altered by others, even against one's will or knowledge by using the Obliviate charm - which Lockhart confessed to doing in CoS and we know that Tom Riddle did to his uncle Morphin and Hoki, the old house-elf, in HBP.

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Well, that's correct, but by 'reusable', I was meaning taking out of the Pensieve after watching, kind of like taking film out of a projector(stupid example, I know). – cst1992 Mar 26 at 6:33
You mean the way Snape kept removing his memories back and forth from the pensieve so that Harry wouldn't see them while they were practicing Occlumency? That would make me ask a different question...Does removing your memory and placing it in the pensieve keep you from remembering it? Have you in essentially forgotten the memory? – Jinoshio Mar 26 at 19:51

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