So, split off from a discussion in another thread, the question is: what is put into a Pensieve, and what are the ramifications?

Is it the memory itself? If so, then it would seem that the originator loses that particular memory. There might be evidence of this when Snape removes the memories of Harry's father and puts it in a Pensieve. I'd always thought that he did it just in case Harry got into Snape's mind. That may not be accurate however.

Is it a copy of a memory? Is that why a memory drawn and put into a Pensieve can be altered as Slughorn's memory was? Like taking a video clip and splicing it together or exposing part of the old film?

That leads to other questions. Can one person absorb another person's memory? If not, why not? What happened if they tried? It's possible that the brain codes every person's memory differently, so one person couldn't make sense of someone else's memory. But if what's drawn is a copy, then the memory's already been put together and decrypted it seems for a Pensieve, which means anyone else could absorb the memory as well.

Anyone else have any thoughts on the subject?

 

I don't think you can put someone else's memory in your own head, that's why a magical device like a pensieve is needed to view them (as you'll be viewing them as an outsider, not from that person's perspective). I think it's a copy, though I think Dumbledore's description could be interpreted in a few ways (the part about having too many memories in his head, and having to withdraw one for undestracted recollection.

I've seen fics where you can buy memories, though it's been awhile since I've seen it. They were pretty much just training videos, but instead of a video, you just watch the memory as many times as you want to learn a spell. The part I don't like is that it suggests that pensieves are common items.

 

I agree with Anarchy that a Pensieve wouldn't be necessary if you could interact with someone else's memories directly. And I agree that Pensieves should be hard to make and rare, so some kind of "training video" memory in lieu of actually going to school wouldn't be feasible for most.

I haven't read the books thoroughly in a while so I could be wrong, but he might've just been obsessively reliving those memories. But it could also be that while the memory isn't removed, the copying process "dulls" it somehow, making it harder for Harry to find and see them.