Operations of a Pensieve

[Bart Lidofsky]

No: HPFGUIDX 164163

Bart:
This is pretty much working backwards, in that I am figuring out what would make sense within the context of the canon.

It appears that the Pensieve stores the records of sensory input from a memory. This allows someone to view the memory as if an outsider (or an outsider to view the memory). As Dumbledore has collected memories from others, it would also make sense that memories in a Pensieve can be copied and restored to their original "owners". The best clue to this is that Sluggy still retains his original memory of the Horcrux question, including the unedited parts. It may well be that putting the memory in the Pensieve in the first place doesn't remove it from the original owner, but there are too many clues that this is not the case.

On the other hand, thought is a complex thing. As has been pointed out, just because the original memory is gone, the memories of the memory, such as the thinking one has done of the original incident, are still intact. And, since the Pensieve only contains the sensory information, one still must retain the subjective aspect of the memories in question. My guess is that, once one puts a memory into the Pensieve, one's thinks of the memory as a story told by someone else, rather than something that has happened to one's self. 

I can see two reasons why Snape empties some memories into the Pensieve. First of all, the phenomenon of "beginner's luck" is usually due to the fact that a beginner will do something that is so disadvantageous that it is completely unexpected to the more experienced person. Most of the time, the experienced person will take advantage of the disadvantage, but, sometimes, the move is such a surprise that it actually works. Therefore, paradoxically, especially during a training session, Harry has a better chance of getting through Snape's defenses than, say, Voldemort (not unlike the way Harry brings down Snape in a duel by unexpectedly breaking the rules in HBP). Therefore, these are memories that Snape doesn't want Harry to even have a chance of seeing. Secondly, as we are told that shutting down emotion is key to occlumancy, it would make sense that Snape would put away memories that have a high emotional content, particularly if they would relate to Harry. 

Bart