[v4dok]

There would be no way to find out if that would be true however. The person in the vat might say they are the same person but you don't know if they really are. Also what happens if you create a copy? Is that two people or is there some kind of shared consciousness? If it is, how do they communicate?

[gat1]

Same with teleportation, you cannot know for sure if the person after the teleportation is the same as the one before, they can just be a copy.